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EK-PS780-TD-001

March 1979

171 pages

Original

12MB

Document:	VAX-11/780 Power System Technical Description
Order Number:	EK-PS780-TD
Revision:	001
Pages:	171
Original Filename:	EK-PS780-TD-001_VAX11780_Power_System_Technical_Description_Mar79.pdf

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EK-PS780-TD-001

VAX-11/780 Power System
Technical Description

digital equipment corporation « maynard, massachusetts |

First Edition, March 1979

The material in this manual is for informational
purposes and is subject to change withoutnotice.
Digital Equipment Corporation assumes no re-

sponsibility for any errors which may appear in
this manual.

Printed in U.S.A.

This document was set on DIGITAL’s DECset-8000
computerized typesetting system.

The following are trademarks of Digital Equipment Corporation,
Maynard, Massachusetts:

DIGITAL
DEC
PDP
DECUS
UNIBUS

DECsystem-10
DECSYSTEM-20
DIBOL
EDUSYSTEM
VAX
VMS

MASSBUS
OMNIBUS
OS/8
RSTS
RSX
IAS

2/80-15

CONTENTS
Page

PHYSICAL CONFIGURATION......... cece ccc eeccceseceeeeceseeeueeeaeeceseaseeeaeeseeeens 3-3
Main Cabinet ..........ccccccccccccseccsececscececececceesteeseeeecceceeesteucesusseuceaeeessuseaeeeneeges 3-3
Unibus Expansion Cabinet.............cccccccccsscscccessceceseeeeeausceesseecceseeeeseessensessaees 3-5

—

POWER SYSTEM DESCRIPTION

WwW

CHAPTER 3

PERFORMANCE SPECIFICATIONS

CHAPTER 2

PURPOSE 20... ceccceccccccccceccnncccnseecueceeeeeeeceeaeeeeaeeeeseceseeteaeceuseeteneeeeneeeenesseneeeasenseeenaes l-1
RELATED DOCUMENTATION...... ooo cccccececeneceeneceesecsesceeseeeeneseeseseeeeas 1-1
SUMMARY DESCRIPTION OF POWER DISTRIBUTION SYSTEM............. 1-]
MANUAL ORGANIZATIONo.oo cccccsncceeesceceecnaeeceeeeeeeeeseneeseeeeaeesuesenees 1-2
ENGINEERING DRAWINGS 2.0.0... cccccccseccaeececeecca cece eesaneesenessaseeaeeeseseeses 1-2

INTRODUCTION

CHAPTER1

3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.2.4.1
3.2.4.2
3.2.4.3
3.3
3.3.1
3.3.2
3.3.2.1
3.3.2.2
3.4
3.4.1
3.4.1.1
3.4.1.2
3.4.1.3
3.4.1.4
3.4.1.5
3.4.1.6
3.4.1.7

VAX-11/780 Expansion Cabinet (H9602-HA/HB).............. cc :scseseseeeeseeeeeenees 3-5

AC POWERDISTRIBUTION... cece ccseceeceeceeeeceeceeeeeaeeeaeeeeenenees 3-5
Power Control Bus............ccccccccsescccesceceseceeeceueceenesesscceeeeeeseeseuseeessensneeeaeeeges 3-19
AC PowerDistribution with 866 and 861 Power Controllers..................008 3-19
AC Power Distribution of Systems Using 869 3-Phase and
Single Phase Power Controllers............ccccccccecceccecseeescsecceseescececesescsseseeceeseses S72)
Controller Functional DeScriptioms ...............cccecccesecceeecuececeeeetenseseeseeneceeaaes 3-4]

869 Controllers .......ccccccccccccsscscesssscsecececeecsecueeesuceecceeeseeeauaesesessseseeeeeeess 3-4]

866 Controllers .........ccccceccecccsecceseceeceueeceeccceseeeeesecseeeauecsececeseeeeeeeesenaes 3-48
861 Controllers ........c ccc cccccecccceeecceeccceececeeceeeeceeeceeseeaeeeceecesseeeesenseeneees 3-50
DC POWER DISTRIBUTION AND GENERATION........ eee ccee cee eeeees 3-50
Power DistriDutiOn ...........cccccccccesscccsscceeneeeeeeceeeeseeeeseseeseeceeeeeaeeeeeaeseeaeeeseerees 3-50
Power Generation - H7100 DC Power Supply............. cc ceeccceeeceateseenaeeeaneees 3-53
GeMeral 00... cece ecceccceeccesececeueecnsensecanecseceaueceeceeuessaeeeecsecegseceeeeaneegees 3-53

Block Diagram DeSCTIPtiONn .............ccccccecceceeeesceeeeeuececeesaeseeeseeaueneesenas 3-67

POWER-FAILURE PROVISIONS... ccc ccccccneccssecseeeesseeeescetesesseeesaaes 3-70
Power Sequencing Circults...........cccccccsececcseeeceseecceseecnececeaueceeeeceeaeseeseeeeauaees 3-70
REQUIFEMEMNIS .........ccccecceeccesecceeeceeceeenccececeneeeeeeaeceeeeeeeeeaeeeeneeeeeeaeeseseees 3-70
SBI Power-Fail Contraints............ccccccecceseccceeeceeceeseccseeeaeecesseeeeeeeeeneens 3-70
Q-Bus Power-Fail Contraints..........cccccccccecccccscecessscseecaceseuseuseusuesenss 3-7]
CPU Comtraimts...........cccccecccsseccsscceeceeseceeceeeseeccseceeeeeauesseeaeecegeseneseaues 3-72
Power System Contraints ...........cccccccccesceseeccececeuseesceeeseesesesseececueeeeeess 3-73
Circuit DeSCrIPtiONn ...........ccceccccsceceseceeneceeeeceeceeeeceeesecsuseeeseesuecesaeeseeeens 3-73
Sequencer Operation .........cceccseccccsseeeeeceeeeeaeecenceseeesaeeceecesueseeseeeeeeees 3-74

111

CONTENTS(Cont)
Page

3.4.1.8
3.4.2
3.4.2.1
3.4.2.2
3.4.3
3.4.4
3.4.5
3.5
3.5.1
3.5.2
3.5.3
3.6

Power Sequencing Terminology............cccccceccecssseeceeeeceeenecesseescessanseseas 3-75
Battery Backup Power Supplies ...............ccccccsssecceecceseeceeeceeesseueeseeessessseens 3-76
H7112 Memory Battery Backup Power Supply................ccccssseeeeseeeeees 3-76
H7111 Time-of-Day Clock (TODC) Battery Power Supply ................. 3-81
Power-Failure Provisions in the H7100 DC PowerSupply...................:000008 3-86
Power Controller Overtemperature Sensor..............cccccseecssscceeceececesececeeseeens 3-87
Air FIOW SeMmsOfrs..........ccccssssceccenssceceueecccceuvcecteusecsauseeseeeneceeeaeceeuesessegueesessees 3-88
CABLING Lo... ei cccccccccssccsececnsccunsceseceneesecseceeuscecsusecseceseeteseeeesenecegustssesegeeeeeesenes 3-88
AC Interconnections. ...........ccccsccccssccesseceseceececsueeesseceuseeeeeeseeseaeceseceseecensnees 3-88
Power ControlSignal Interconnections...............ccccceccceseeceescceeceeeecaneceeeseenes 3-89
Backplane DC Interconnections............ccccecccecsseccaceeeeeeenecessnesceeesceesaueesesees 3-89
GROUNDING LL... eee ccceccsseceueeceeeeeeneccaececescecsecnaceeeusecaeeceusegesseesenenstaseesees 3-89

CHAPTER 4

H7100 DC POWER SUPPLY FUNCTIONAL SECTION DESCRIPTIONS

4.1
4.2
4.3
4.4
4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
4.4.6
4.4.7
4.4.8
4.4.9
4.5
4.6
4.6.1
4.6.1.1
4.6.1.2
4.6.1.3
4.6.1.4
4.6.1.5
4.6.1.6
4.6.1.7
4.6.1.8
4.6.1.9
4.6.2
4.6.2.1
4.6.2.2
4.6.2.3

GENERAL... cce cc ccccccescccesscecenceeaesceceeeeeeesesecueceeenseseusseeeucecaecenseessaeeceuesensaess4-1
FRONT PANEL (AC INPUT ADAPTER))........ 0... .ccccccccccccseeceeeseceeeseeusecsuesetenees4-9
MIDDLE PANEL... cece cesceccnsececeeseceensceceneceauscecencessueceagecesecesseeeeaueseeagess4-9
MOTHERBOARD 7.0... ce cc cecccesececeeeceeeceeeeccuececesceceseaueecsucecseeeeectsusesnnseesseseees4-9
Start-Up and AC Sense Transformer (MB1)..............ccccccessseccsseeceaeeseceneeseeees4-9
Raw DC Supply........cccccccccccssecceseceaecceseeceeecenscensusesecceueceeecesenecseseeasessaneeaaes4-12
Power Switch and Base Drive Transformer.................ccccceescceeccesceeceeeecsenes4-12
Snubber Networks............ccccssscccssecccseecceesscceenececesceseeeeceeceseseeeeseessesegeg senses4-12
Reset DIOdes ..............cccccseccsssccsusccusecsuecenssceeeseceueccescseesseeeessnceseeessussseeseegeees4-12
Raw DC Semse..........cceccccecssscccecceucececcuscecsneseeeceneeeeecescseuceseceeeeceeseuceeneceesages4-12
CIOWDAL........cccecccssccneccnseccencecescecsnscuseceesseceueesauucesnecegectsaeesenesaesauecessasesseeegs 4-12
+30 Vdc Section ..........ccccccescccssccsseeccsecceuececsscesesceeeeeeseceeeseseceeesseseeauseneeeeees4-12
Floating 30 Vdc Section 00... cceccecccescceseccseceeuecesecuceenseeeeeueteseeeuseeecessassuees4-12
REAR PANEL 2.0... ceccceccccncccnscceseceeeecseeccsaecesnseceneceescsaeeceseceseeeaueetsaecesseeagaes4-12
BIAS/CONTROL BOARD. .... icici ceecccececeeeeeeeceeeeeeeeneeeeeeeeeaeaaeaaaaaaaeeeeteenesseees4-14
Bias/Control Power Supply ............cccccccccccccensssseeceececceseteusaseeceeeseeseusaneeens4-14
Snubber-Suppressor (BC1) ...........cccccsssceccsscccnseeceeeceeseeeeeceeuecesuaeseeeenss4-14
Bias Power Switch (BC2) ..........cccceccccsscecceeecceeceseeecceseecesceseuecenseseeeanes4-18
+12 V Bias Supply (BC3)............ccceccceccesescccesecnenseeecceeeeceeeseeeeaseeseneees4-18
5 V Bias Regulator..........ccccccccsecseccceceseecscccuceesececcuseeseusceuseeceenseenseeceeess4-18
Power Switch Driver (BCS).............cccccccesesesecsececeeseceecesasseueceeseuseeseeeess4-18
Bias Ramp Generator (BC7)............ccccsscccsseccescceseeceecesusceeecenscecenseneneees4-18
Bias Clock (BC8) .........cccccscsccccseceeessceceseeceenccceeucssceseaueeecseeaueceseeeesegass4-18
Bias Pulse Width Modulator (BC9)..............cccceccccseccsscceeeeeerecsseeeeneees4-18
Start-Up Supply/AC Monitor (BC10) ....... ee eeeeeeeeeeeeeeeceeeeeeeneeaeanes4-18
$5.1 V, 100 A Regulator... ccc ccccccssececnseeccesuscecececeeseseeseeseceeseeesseeseeeenes4-18
Feed-Forward Circuit (BC11)............cccccccsecccsecccesseceseceeueceseecseeaeeeeeaees4-19
5. V/100 A Control Amplifier (BC12) 0... eeeeccceccsssseeeeeeeeeeneesneeeeees4-19
Ramp Generator (BC13)............ccecccccccececessceeeeeeseeeceneseaceeusceeceseseeeseeecs4-19
iV

CONTENTS(Cont)
Page

4.6.2.4
4.6.2.5
4.6.2.6
4.6.2.7
4.6.2.8
4.6.2.9
4.6.2.10
4.6.2.11
4.6.2.12
4.6.2.13
4.6.3
4.6.3.1
4.6.3.2
4.6.3.3
4.6.3.4
4.6.3.5
4.6.3.6
4.6.3.7
4.6.3.8

4.6.3.9
4.7
4.7.1
4.7.1.1
4.7.1.2
4.7.1.3
4.7.1.4
4.7.1.5
4.7.1.6
4.7.1.7
4.7.1.8
4.7.1.9
4.7.1.10
4.7.1.11
4.7.1.12
4.7.1.13
4.7.1.14

4.7.2
4.7.2.1
4.7.2.2
4.7.2.3
4.7.2.4
4.7.2.5
4.7.2.6
4.7.2.7

20 KHz Clock (BC1A4) oo... ccccccsseccneseceenecenseceeenecseeeeeeegesensencesseeeees4-19
Pulse Width Modulator (BCI15) ....................dea eecaeeeeeeeeesesseseesaeeeuseeaues4-19
Control Switch (BC16)...........cccccesccescccsseceeeceececeesecseeeuseauesesaeeseneeeees4-19
Power Switch Driver (BC17) ............ccccccessscccsseeeeeseecesceseseccesueceeneeseeeaes4-19
Turn-Off-Drive Buffer (BC18) .............ccccccessceeccescecesseescusseneseeseeseseess4-19
Reset Sense Circuit (BC19) oo... ccccessscceesecceescereseeeeececueseeeaeeeenenes4-19
Power-Switch-Fail Detector (BC20).............cccccessccescccesecescecessseeeseneees4-19
5 V/100 A Overcurrent Detector (BC21)......ceeeseeeeeeeeeeeeeeeeeees4-19
Crowbar Detector (BC22)............cccccccccssecccscecenseccneceesausessensesseeeeseneens4-20
Peak Primary Overcurrent Detector...............cccccccssseececeeseeseceeseesaeeeeees4-20
Protection and Status Circuits............cccccccsssscccsssccceseececsaeeeceeeeeeeeseesecseaeesens4-20
AC LO (BC24)... ccc ecccceccnsecccseceeseeceeceeseceeeseecesencessnsecuseeueeetseecnen senses4-20
DC LO (BC25) .o.cc i ceccccccecccccsssceceeesceeescenensecceaeeeeecseuscessaceessuaeeseaeeeeeas4-20
—9 Vde Source (BC26) 0.0... cecccccecescccescceseccnscssseeeesecsaceceaeesessessaeeages4-20
Output DC LO Detector (BC27) 00... eccccssseceesecetsneceseueeeeeeeeeeeees4-20
Regulator-Fail Gate (BC28)..............ccccccsseccsssccsseeceeeceeseeeseeeeeeeeeeeeeeees4-20
Run-Up Reset Buffer (BC29) .0.......e ee ccccsesececsseseceeesceeeaeescetessessaeseees4-20
Slow Run-Up Circuit (BC30)....... cc cccceccscccsseeceesceceeeeeenscesssnceeanecsaees4-20
Initial Turn-On and DelayCircuit (BC31)....... ees cceeeceseeeeseereeeenGed I
Relay Driver (BC32)...........ccccccccseccseccssteeccuseceecenssseeeccensteuseeeeseeseneeceees4-21
REGULATOR OPTIONS... cece cceccccesecceseececescceeneseeeeceeeaseceuecessaueseeaneeuenes4-21
H7101 (-5.2 V) Regulator .......... cc ceccccescccesececesceeeeeeeeececeeseseusecessgeeeasenes4-21
Base Drive Circuit ...........cccccesccsseccessccescececeneusseusceeuseeseeseeussessestenseageres4-21
Power SWItch............ccccccsscccssccceneseceseeceeeecceecceeseceeeeseseenecseseeeenneeseneeenes4-21
Output Filter... ces ccsseccccssececeeeeeceseecesansececseseceseeeeseesuseseesenetenses4-21
Overcurrent Circuit ..........ccceccccecccesecesescueccenececeseseucceeececeeceseueceeseteusenes4-23
Error Amplifier ...........cccccscccseecsecccsccceseecuscesesceuccecsceescseussessessneseneses4-23
RAMp GeNeLatOr .........ccccccceecceeccencceescnceseceseecucenseseseeuceensceecenseneeesees4-23
Pulse Width Modulator (PWM).............cc.:sssceccccssessceceessseeceeseeeesessaees4-23
20 KHZ CLOCK 200... eecccesssceceescceseceeenseeeeeseceeeaseceseusceeseuueecessanseesnes4-24
Turn-Off-Drive Circuit .............cccccccsscceeseceenececeeceeeesccseesessusseseusessestens4-24
Flyback Di0de.........ccceccceccceesccescceececssececcesseseussssesaeeseusesseeesteeesenenes4-24
DC OK Circuit ........ ccc ccccceescccesceecsceenececeseceeesceneeeecceseeseeuseeeeaeesenseesees4-24
CrOWDAL 2... cece cecccessccaneccascceneceeecceueceeseeeeceseseceaceeeseseeceatecceeseaeseegeseaees4-24
Voltage Reference..............cccccccsssecccesececseeeeecensceceeeseeeeueeseceaensseeegaeseanes4-24
Slow Run-Up Circuit... ecccesecceeccneeccsscessecseescneeeceeecesenseesesenenenes4-24
H7102 (4:12 V) Regulator ........ ccc cccccsscccneccceececceseccesessensseceseeseessaeensuees4-24
Power SWItch............ccccccsscccsscecenccecsceneececeececsscecseesenesesseeesessueseauasesees4-25
Power Switch Diver...........cccccccsscccseccescecseceseetenscesuceeeceeuseeseceseseeeeees4-25
Output Filter oo... cecccsecceseeeeseeceneceececeeceensseceecssecceueesenseeenseeeees4-25
Overcurrent Circuit ..........cccccscccssscccescceseceascecencceauesesseesesseseeeeseesaeeeas4-25
Error AMplifier ...........ccccccesccceeccccsscceesecesececeescceuceceeenceseuncessesensessenaess4-25
Ramp Generator.........ccccccceccccecceesceceeeceecscueeeeceesseueuseeusseussueeseuseeaseeees4-25
Pulse Width Modulator ...........cccccccecccsscccsscecssecceescceeenesceeeceaeeceeeestenees4-25

CONTENTS(Cont)
Page
4.7.2.8

20 KHZ CLOCK... ccc ccecccceeccceesecensecececeeescceeeececuceceusecsaueceesceceseceeeneesees4-27

4.7.2.9
4.7.2.10
4.7.2.11

Turn-Off-Drive Circuit .............cccccccescccescceeccecececsesscnsseseescecuseceseaeesees4-27
Flyback Di0de..............ccccccsesseceenscecceesececessceeeeecessseecsuucesssensesenseseesees4-27
DC OKCircuit....... ccc ccecccssssecneessecceeesceceesceaueecesseaeccseuececeegessessueseeenes4-27

4.7.2.13
4.7.2.14

Voltage Reference...............cccccccsecccecesseceesceensuseceeusccsceeeesscusseeeeansecenenees 4-28
Slow Run-Up Circuit.........cccccccsssssseececcecaeeesessecececccceseauegeseseeseeeeeeseeeas 4-28

4.7.2.12

4.7.3

4.7.3.1

4.7.3.2
4.7.3.3
4.7.3.4

CLOWDAL..........cccccssscccsscecescesnsccesceceuceesseeceensenseceseuscesaeeeseneetseeeessesenes 4-28

H7103 (£5 B) Regulator ............cccccccccccccsscccsssccceeescceesscecsuesceeauseeeseegeseesguses4-28

+5 VB Regulator..........ccccccccccssscecsecceescceeecceeecccseneseneceeseesseceeegecenes4-28

—5 VB Regulator..........ccccccscccccesececescceesccuseecesecccsueeceaeeeeeuscetsneeeaeaeesses4-31
12 V Bias Supply for —5 VB Regulator............. ccc cceccceeccsesccneeceeeeeeeeeeees4-32
Status and Sequencing Circult............ccccceccccsescceeseceeeeeeeeseesesceeeseeeaeees4-32

APPENDIX A

GROUNDING

APPENDIX B-

H7100 POWER SUPPLY AND REGULATOR REPLACEMENT

FIGURES

Figure No.

3-1
3-2
3-3
3-4

Title

Page

VAX-11/780 Control Panel on Main Cabinet... ccc cceeeccccccessnssseseeeeeeeeeceeeeneeens 3-2
VAX-11/780 Basic Configuration ...........:..cccccccceccceeseseeeecececceaeaneesseeeeeeeeeeeseaeaaae oes 3-4

3-5
3-6
3-7

Equipment Space Allocation in Add-On Cabinets (Front View)..............ccssssceseeees 3-6
Space Allocation for DZ11-A Multiplexer and RK611 Controller in
BA11-K Mounting Box ............ccccccccssccsccceecessensceeeccecuceeecesceeceseeeeceeecenseageeneeeees 3-7
BA11-K 10.5 Inch Mounting Bok ...............cccccccesccesseceeeeceeseceencesseeeceeeceeseecessaeeegee 3-8
H765 Power Supply Assembly ................ccccccsscccesceeseceeeeeeceeseceescesaeeceeeseeeaeaceseeseaes 3-9
VAX-11/780-C/D Main Cabinet (Front View, Cabling Data) .......... eee 3-10

3-9
3-10

Simplified Block Diagram — 866 and 861 Power Controllers................cccccceeseeeeees 3-18
VAX-11/780 AC Power Distribution System Using the 866 (3-Phase) and

3-8

VAX-11/780-C/D Main Cabinet (Rear View, Cabling Data)...........ceeeeeereees 3-13

861 (Single Phase) Power Controllers... eee ccsescesseeeeeeeeeeeeeeneeseeeeeereeseeeaees 3-21

3-11

VAX-11/780 Main Cabinet Power Distribution (3-Phase, 120 Vac, 60 Hz).......... 3-23

3-13
3-14
3-15
3-16

3-Phase Power Controller .............cccccccssseccssececceneececneceesuseceeauseceauaceeeeeesceessesssenses 3-25
869 Power Controller — Simplified Block Diagram .................ccccccccsececeeeeesueseeeeees 3-27
869D Power Controller (Front View).............cccccccsseceseeceseceescenseceeeseeeusseeeecssneeanes 3-28
869D Power Controller (Rear View).............ccccccsscecsssccessccenscecensetenscetsueeeeueseeeeees 3-28
869E Power Controller (Front View).............c.ccccccesccscccceceeuscceseceeuecececeucnseassceeaes 3-29

3-12

VAX-11/780 AC Power Distribution System Using the 869

FIGURES(Cont)

Figure No.
3-17
3-18
3-19
3-20
3-21
3-22
3-23
3-24
3-25
3-26
3-27
3-28
3-29
3-30
3-3]
3-32
3-33
3-34
3-35
3-36
3-37
3-38
3-39
3-40
3-4]
3-42
3-43
3-44
3-45
3-46
3-47
3-48
3-49
3-50
3-51
3-52
3-53
3-54
3-55
3-56

Title

Page

869E Power Controller (Rear View).........c..cccccceccececseccueeseuceeecceuseeusseuseeessusceeeeeees 3-29
866D Power Controller (Front View)...........cccccccecsssceccsccesecssscscessesceeseuseueseneeeses 3-30
866D Power Controller (Rear View) .............ccccccccsecseccecceeccesseneeeesenstseeeesecseaueeeess 3-30
866E Power Controller (Front View) ..........cccccceccceeccecececeseeesenceeuecuseeeeeuseeceeeseuss 3-3]
866E Power Controller (Rear View).............ccccesccccecsscceeeteueteueceeceeeeceeeseeseeesenenetes 3-3]
7015036-00 Air Flow Interface (+15 Vdc Power Supply)...............cccccescceeseeeeeeeees 3-32
869C Power Controller (Front View) ............ccccecccesccseecesccesceeneceeceesceeeeseeseeseeesees 3-32
869C Power Controller (Rear View)............ccccccccccesececscecescccescesseeeessusessaseeeeeeees 3-33
869B Power Controller (Front View) ............ccccccccccseccescecesceeeesceueceeuceeseseeeueeeeseaes 3-33
869B Power Controller (Rear View) ...........ccccccccccccsscecceeccucceseeesseseceseuceusseeseeeseees 3-34
861C Power Controller (Front View)..............cccccececesccceneceesecaececesceaseceeeeeeaeesseuses 3-34
861B Power Controller (Front View) ...........c.ccccccccecceeceecseecdesceeceseeeececeeseeeeeuestass 3-34
869 Power Controller Input/Output Relationships - LOCAL ON Mode............. 3-38
869 Power Controller Input/Output Relationships -OFF Mode.................008 3-39

869 Power Controller Input/Output Relationships -R EMOTE Mode............... 3-40

869D Power Controller Block Diagram ................cccccccececesesecseeeceeeeeeneceeeeeeceeeneees 3-42
Simplified Diagram of Air FIOW Sensor ..............cccccesccesccescecesseessseeeseeeesseuseeaueens 3-43
Schematic of 869D 3-Phase Power Controller ..............cccceccccssccseceeeeeeeeceeeeeeaeeees 3-45
866D Power Controller Schematic ............c.ccccccecccsssssceeeesesececeseseeceeeageeeseeeueseeseees 3-49
866E Power Controller Schematic...............ccccccsssscecceeeeceeeececeaescceeaeceeseeseseasaeeeens 3-51
Main Cabinet DC Power Distribution .............. cc ecccceeccceseeeceeeeeeeececeeeeeeseceaueeesees 3-52
Basic Conceptof a Switching Regulator.............ccc cc ccccceccssccesceeucceeceenscesseenecnseseecs 3-54
H7100 DC PowerSupply — Functional Block Diagram...............cccecceceecceeeeseee anes 3-55
Block Diagram of Typical H7100 DC Power Supply Regulator..................c 3-56
H7100 Power Supply — Rear Panel Connectors...............cccccccccesceeeeceeeseseeeeneceeees 3-58
Decals Showing Regulator Complement of H7100 Power Supplies..................... 3-59
H7100 DC PowerSupply — Top View ............ccccsecceccccaseseeeeceeececeeaeeeeeeeseseeeeeeeues 3-62
H7100 DC PowerSupply Front Panel AC Input Adapter (Front View)............... 3-63
H7100 DC PowerSupply Front Panel AC Input Adapter (Rear View)................ 3-64
H7100 DC Power Supply - ComponentIdentification
(Front and Rear Panels Detached from Chassis) ................ccccceccescccseeeeecenssenseeeees 3-65
H7100 DC Power Supply - Component Identification
(Front and Rear Panels Attached to Chassis) ................cseccseccsscesecceeeeeseeseeseeeeees 3-66
Control Circuit Simplified Schematic - H7100 DC Power Supply....................... 3-69

POWER DOWN/POWER UP Timing Diagram for

SBI Power-Fail Conditions.............ccccccesccescceeeecceeecceseeeusccaeseeausesauecsasessesensueeeaaes 3-71
POWER UP/POWER DOWNTiming Diagram for Q-Bus
Power-Fail Conditions ..............ccccsccccsscecaceceeeeeteeesceeeeseececeeeeeceseaseeaeesesaueeseqeeeens 3-72
Power-Fail Sequencer — Inputs and Outputs .............ccccceccccessscccneeeeeeseeeeeeeesenenas 3-75
H7112 Memory Battery Backup Power Supply — External View...................:0c0008 3-77
H7112 Memory Battery Backup Power Supply — Interior View ...................0000008 3-78
H7112 Memory Battery Backup Power Supply — Electrical Schematic................. 3-80
H7111 Time-of-Day Clock Battery Power Supply ............... cc ccccccecssceeeseseeeeeeeeeeees 3-82
H7111 Time-of-Day Clock Battery Power Supply - Block Diagram.................... 3-84
Vil

FIGURES(Cont)
Figure No.
3-57
3-58
4-]

4-2
4-3
4-4
4-5
4-6
4-7
4-8
4-9
4-10
4-11
4-12
4-13
A-|
A-2
A-3
B- 1

Title

Page

H7111 Time-of-Day Clock Battery Power Supply - Timing Diagram.................. 3-85

Grounding Details for RP05/06 Drives 0.0... cccccceeeecceeeceeeeeeececeeasaeeseeeeseneees 3-90
H7100 Power Supply - Connector Locations
(View from Right Side Looking Toward Motherboard)...............cccccccssseceeeseeeeneees4-2
H7100 DC Power Supply —- Component Identification ............. cc ecccceeeceeeeeeeeeeees4-3
H7100 Power Supply Interconnection Diagram ................ccccsssccesceceseeececaeceeeeeeeees4-4

H7100 Front Panel /Middle Panel Block Diagram ................cceecceeestseeteeeeeeeneeens4-10

H7100 Motherboard Block Diagram ................cccccccccescseecuseeeeeceeeccustesetenseeereesenes 4-11
H7100 Rear Panel Block Diagram 2.0.0.0... cccccccccccccecceeccenseceeeeeeecesseeceeseeeeceeees4-13

H7100 Bias/Control Board Block Diagram ...............ccccccsseseesceceneneeeeeeceeeeene totes4-15

H7101 (-5.2 V at 30 A) Regulator Block Diagram. ............ cece cesccceeeseeeseeeeees4-22
H7101 Regulator Timing Diagram ................ccccccccscccseeceeeceeneceeeeccesceueseeeneessseeaaes4-23
H7102 (+12 V) Regulator Block Diagram ..............ccccccccccssscccaeeeeaeeceseeeeeeeeeeneeess 4-26
H7102 Regulator Timing Diagram ................ccccccscecceeceeneccensccseseceeeeessensuceseseaneees4-27
H7103 (£5 B) Regulator Block Diagram ............. ccc eeccseccescceesceceeeceeeeeneceanseeaaes 4-29
PWM Timing Diagram for +5 V Switching Regulator of H7103 Board..............4-3]
Lightning Stroke Current Path
(Shown with System Groundedto Building Steel) ........... ccc ceecccseecceeeeseneeeenees A-2
Earth Ground Stake (Ground Rod).............c cc cecccescccseeeeseceeneceeneeeeeceeseetesegeeeeeneees A-5
Ground Reference Distribution ...............cccccescccssccceeeceeseeeeeeceeeceeceeseeseeecneceeeeeeees A-7
Basic H7100 DC Power Supply, Regulator Boards, Cables and Harness
for Corrective Maintenance on Failed DC Supply................ccceecccsssecesseeeeeeeeeeeeenes B-2

TABLES
Table No.
1-1
1-2
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
3-1
3-2

Title

Page

Available Related Documents.............ccccieccccsssccesesccnesecuesceceeeceeeceaseecsueeecaaeseanaees 1-1
Reference Schematics and Wiring Interconnection Diagrams...............ccceecesseeeeees 1-2

VAX-11/780 Main Cabinet Specifications.............cccccccccccesnseseseetececeeecesseuseseseeeeees2-1
Model 869D/E Power Controller Specifications .............cccccessesseseeeeeeeeeeeeaeeeeees2-3
Model 869C/B Power Controller Specifications ......... ec cecsceeseeeseeeeeeeeeueaneeseees 2-6
Model 866D/E Power Controller Specifications........ ee ceeseseeeceeeeeeaeeeeeeeeaeeees2-8
Model 861B/C Power Controller Specifications. ...........eeeeeeeeeeeeceeeeteeeeeeeeeeenees2-11

H7100 DC Power Supply Specifications...............ccccescccsscccesceccseseceecessesesseesennenss 2-13
BA11-K Mounting Box - DC Power Supply Specifications..................cccccceesceeees 2-15
H7111 TODC Battery Power Supply Specifications .............. cc ceecccsececeteceessseeeeeees 2-19
H7112 Memory Battery Backup Power Supply Specifications..............ccccccsseeseees 2-20

Standard DEC Power Controllers Used in VAX-11/780 Systems... eee 3-16
Power Cords, Plugs and Receptacles for Controllers Used in

VAX-11/780 Systems .........:ccccecccccccenesseeseececeeecenaeenaaaensceececeeeeeasaaaneseeeeseeeeeanenaeges 3-17

TABLES(Cont)

Table No.

3-3

Title

Page

Comparison of 869D and 866D 3-Phase Power Controllers...............c.ccccccseeeeeeees 3-36
Comparison of Major Component Differences in 869 Power
Controller Family.............cccccccccsscccscccnscecsscccseccseesuseeeseseaecseeseseeeeeessneeeeaseeeeeenas 3-4 /
Comparison of Regulator Features in H7100 Power Supplies....,.............cccceeceeees 3-57
H7100 Power Supply Output Connectors J6 and J7.- Pin Identifications............. 3-60

VAX-11/780 DC Power Supply Options............ cc cceeeccsceeceeceeeeaeesseeseseeseeeeseesseneas 3-61

H7100 Power Supply Regulator Options................cccccccssecsseecesecceectenseeeeceesceenes 3-61
VAX-11/780 Battery Power Supplies... ee eeseeeceecceneaeeeseaeeeseeeeeeeeeeeeeneaags 3-61

H7100 DC Power Supply Battery Adapter (Connector)

J2 — Pin [dentifications 2.0... cecccscccscecesceceseceeeecuecccsceeecceaeceenectuseseeseseeeesaneeses 3-67

CHAPTER 1
INTRODUCTION

1.1 PURPOSE
This technical description provides all presently available information on the VAX-11/780 Power
System. The purpose of this documentis to provide DIGITAL field engineers, and/or customerpersonnel trained by DIGITAL’s Educational Services, with an engineering-level understanding of power
control and distribution within the system.
12

RELATED DOCUMENTATION

Table 1-1 lists available related documents.
Table 1-1

Title

Document No.

Notes

861-A,B,C,D,E,F Power

EK-861AB-MM-002

Available on microfiche

BA11-K User’s Guide

ED-BA11K-OP

Available on hard copy

BAI1-K 10.5 Inch Mounting

EK-BA11-TM-003

Available on microfiche

Controller Maintenance Manual

Box Technical Manual

Available Related Documents

SUMMARY DESCRIPTION OF POWER DISTRIBUTION SYSTEM

Centralized control of the ac and dc power within the VAX-11/780 systems is made possible by the 3phase or single-phase powercontroller used in each of the cabinets, exclusive of peripherals. Control is
effected through a key-operated switch on the control panel of the main cabinet (refer to Figures 3-1,
3-2 and 3-3) and the DEC power control bus that interconnects all power controllers and enables
normal power-up and power-downroutines as well as emergency shutdownin response to such sensed
conditions as overtemperature and insufficient air flow within the main cabinet.
The powercontroller in each cabinet receives its primary ac power from a separate customer-provided

receptacle. In the VAX-11/780 main cabinet, the 3-phase controller distributes 120 Vac or 240 Vac

single-phase powerto the dc powersupplies, to three blowers, an 11/03 microcomputer, and an RXO1
floppy disk. The H7100 dc powersupplies (up to five, depending on the system configuration) provide
the regulated —5.1, -5.2, and +12 Vdc required by the system.
The 3-phase controller for the VAX-11/780 main cabinets and SBI (synchronous backplane interconnect) cabinets shipped prior to June 1978 is the DIGITAL 866D (120/208 Vac) or 866E (240/416

Vac). Shipments subsequent to that date use an improvedversion of the 866; 1.e., the 869D or 869E.

Unibus expansion cabinets shipped prior to September 1978 use the single phase 861C (120 Vac) or
861B (240 Vac) controller. Shipments subsequent to that date use an improvedversion of the 86]; 1.e.,
the 869C (120 Vac) or 869B (240 Vac).
1-1

This manualdescribes the equipment configuration of each cabinet in a basic VAX-11/780 system and
shows its physical and electrical relationships to the power distribution system. For corresponding
details on VAX-11/780 peripherals, reference should be madeto the appropriate manual or manuals
for each.

14 MANUAL ORGANIZATION
The principal specifications for the VAX-11/780 main cabinet, the power controllers, H7100 power

supply, the power supply (H765) for the BA11-K mounting box, and the battery backup supplies
(H7111 and H7112) are given in Chapter 2. Chapter 3 is a system-level technical description covering
the system configuration, the ac powerdistribution, the dc power generation and distribution, powerfail provisions, and cabling. Chapter 4 provides a block diagram-level description of the H7100 dc
power supply, including regulator options. Appendix A is a general discussion of grounding considerations extracted from the Corporate Site Preparation Manual. Appendix B coversthekitting provi-

sions for corrective maintenance on the H7100 dc powersupply.
15

ENGINEERING DRAWINGS

Table 1-2 lists reference schematics and wiring interconnection diagrams containedin thefield maintenance print set for the power distribution system units used in VAX-11/780 system configurations.
Table 1-2

Reference Schematics and Wiring Interconnection Diagrams

Title

DEC Dwg.No.

No.of Sheets

11780 System Power Diagram

D-IC-11780-0-1

11780 Subsystem Interconnect

D-IC-11780-0-3

869D Power Controller
869E Power Controller

D-CS-869-D-1
D-CS-869-E-1

l
l

H7100 Interconnect Diagram
Motherboard STAR (H7100)

E-IC-H7100-0-3
D-CS-5412550-0-1

-5.2 V Regulator Board
+12 V Regulator Board
5 V Regulator Battery
Status Card

D-CS-5412554-0-1

l
l

D-CS-5412560-0-1
D-CS-5412556-0-1
D-CS-5412558-0-1
D-CS-5412562-0-1

Bracket AC Assembly
H7112 Interconnect Diagram
Battery Charger

E-AD-7014122-0-0
C-IC-H7112-0-3
D-CS-5412675-0-1

I
2
l

T.O.D.C. P.S. and Backup

D-CS-5412763-0-1

11780 System Interconnect Diagram

H7100 Bias/Control

D-IC-11780-0-2

|
l
l
l

CHAPTER2
PERFORMANCE SPECIFICATIONS

This chapter summarizes the performancespecifications for the major elements of the VAX-11/780

OWI AARWN-

powersystem.

Main cabinet (Table 2-1).
Model 869D/E 3-phase power controllers (Table 2-2).
Model 869B/C single-phase power controllers (Table 2-4).
Model 866D/E 3-phase powercontrollers (Table 2-3).
Model 861B/C single-phase powercontrollers (Table 2-5).
H7100 power supply with H7101, H7102 and H7103 regulator options (Table 2-6).
H765 power supply of BA11-K mounting box (Table 2-7).
H7111 TODC Battery Power Supply (Table 2-8).
H7112 Memory Battery Backup Power Supply (Table 2-9).

Table 2-1

VAX-11/780 Main Cabinet Specifications

PHYSICAL CHARACTERISTICS
Cabinet Type

Double-Width Highboy

Height

152.4 cm (60 in)

Length

118.8 cm (47 in)

Depth

76.2 cm (30 in)

Weight

595.0 kg (1200 Ib)

ELECTRICAL CHARACTERISTICS
AC Power

Full Load

120/208 V, 3-phase, 50/60 Hz

6.0 kVA nominal; 7.2 kVA maximum
240/416 V, 3-phase, 50/60 Hz
6.0 kVA nominal; 7.2 kVA maximum

Voltage/Frequency Tolerances

100-127 Vac (phase to neutral)

47-63 Hz

200-254 Vac (phase to neutral)

47-63 Hz

Table 2-1

VAX-11/780 Main Cabinet Specifications (Cont)

ELECTRICAL CHARACTERISTICS(Cont)
Current
Steady State

20 A/phase; 20 A in neutralline

Surge (powerturn-on)

150 A/phase

Surge Duration

5 ms at 120/208 Vac

Power Cable
Length
Plugs/Receptacles

869D/E Controllers
866D/E Controllers
DC Power

4.5 m (15 ft)
(Table 2-2)

(Table 2-3)
Refer to H7100 Power Supply
Specification (Table 2-6)

ENVIRONMENTAL CHARACTERISTICS
Temperature
Operating

15° to 32° C (58° to 95° F)

Non-Operating

-40° to 60° C (-40° to 151° F)

Relative Humidity
Operating

20 to 80% with maximum wet bulb

25° C (77° F) and minimum dewpoint 2° C (36° F)
Air Flow at Inlet

705 1/s (1500 ft3 /min)

Altitude
Operating

2400 m (8000 ft), maximum

Non-Operating

9100 m (30,000 ft), maximum

Heat Dissipation

5500 kg cal/hr (22000 Btu/hr) 6450 W
2-2

Table 2-2

Model 869D /E Power Controller Specifications

AC INPUT

869D
869E

Phase
WJ

Voltage

Phase-to-Neutral

Nominal

90-132 Vac
180-264 Vac

120 Vac
240 Vac

Frequency |

869D
869E

47-63 Hz
47-63 Hz

Current Capability

869D
869E
Input Power Capability

869D
869E

24 A/phase at 120 Vac
12 A/phase at 240 Vac
Full Load

8.640 kVA
8.640 kVA

Inrush Current Capability

869D
869E

450 A peak for 1/2 cycle at 60 Hz

225 A peak for 1/2 cycle at 50 Hz

Input Overvoltage Transient
(power controller only)

869D
869E

150 V for 1 s, phase to neutral

300 V for 1 s, phase to neutral

Leakage Current Contribution
(power controller only)

869D
869E

1.5 mA at 250 V, 50 Hz
1.5 mA at 250 V, 50 Hz

Circuit Breaker Rating

869D
869E
Primary Power Connections

869D
869E

30 A/pole (4 poles) with inrush protection
15 A/pole (4 poles) with inrush protection

3 phases, 120° displaced
120/208 Vac wye, 4-wire plus safety ground
240/416 Vac wye, 4-wire plus safety ground

2-3

Table 2-2

Model 869D/E Power Controller Specifications (Cont)

AC INPUT(Cont)
AC Connection

869D

Power Cord — 7015253
Receptacle — 12-123 15;
Hubbell 2810; NEMA L21-30R

869E

Power Cord - 7015254
Receptacle — 12-14378-02*;
Hubbell 52OR7; NEMA N/A
Without powercord — Five 10-32 studs

CONTROL PARAMETERS
Thermoswitch (exposed to
outside ambientair)
Opens contactorat
Automatically resets at

71°C (160° F)
49° C(120° F)

Input-Signal Current Levels
High
Low

500 wA maximum

20 mA maximum

Input-Signal Voltage Levels
High
Low

3to35 V
Oto 1.8 V

Connectors

Female (3)

Male (3)

Power Control Bus

DEC 12-09350-03 with DEC 12-09379 pins
DEC 12-09351-03 with DEC 12-09378 pins
Meets DEC Standard 123:
Pin 1 - Power Request
Pin 2 - Emergency Shutdown
Pin 3 - Ground

Air Flow Sensors

Texas Instrument 2SE (DEC 12-14447)

AC OUTPUT
Duplex Receptacles

869D
869E

9 (120 Vac, 20 A; J11-J19)
9 (240 Vac, 15 A; J11-J19)

*DEC-supplied with the 869E Controller.

2-4

Table 2-2

Model 869D/E Power Controller Specifications (Cont)

AC OUTPUT (Cont)
Circuit Breakers

869D
869E

20 A perduplex outlet
None

Maximum Output Current/Phase
869D

Phase 1 (J11, J12, J13)-24A

Phase 2 (J14, J15, J16)-24A

Phase 3 (J17, J18, J19) -24 A
869E

Loads

Phase | (J11, J12,J13)-12A
Phase 2 (J14, J15, J16)-12 A
Phase 3 (J17, J18, J19)-12 A

CAUTION

No loads external to the cabinet are to be plugged
into the controller.

MECHANICAL AND ENVIRONMENTAL
Size
Height
Width
Depth

12.7 cm (5 in)
48.26 cm (19 in)
25.4 cm (10 in)

Weight

13.5 kg (30 Ib)

Cooling

Convection

Mounting

48.26 cm (19 in) rack

Temperature
Operating

5° to 50° C (41° to 122° F)

Non-operating

-40° to +66° C (-40° to 151° F)

Humidity

10 to 95% with maximum wet bulb 32° C (90° F)
and minimum dew point 2° C (36° F)

2-5

Table 2-3

Model 869C/B Power Controller Specifications

AC INPUT
Voltage

Phase

Range

Nominal

869C
869B

l
l

90-132 Vac
180-264 Vac

120 Vac
240 Vac

Frequency
869C
869B

47-63 Hz
47 - 63 Hz

Current Capability

869C
869B

24 A/phaseat 120 Vac
16 A/phase at 240 Vac

Input Power Capability

869C
869B

2.88 kVA (full load)

Inrush Current Capability

869C
869B

540 A peakfor 1/2 cycle at 50 Hz
270 A peak for 1/2 cycle at 50 Hz

Input Overvoltage Transient
(power controller only)

869C
869B

150 Vforls
300 V for ls

Leakage Current Contribution

(powercontroller only)
869C
869B

1.5 mA at 250 V, 50 Hz
1.5 mA at 250 V, 50 Hz

Input Circuit Breaker
869C
869B

30-20-20 A with inrush protection
20-15-15 A with inrush protection

Primary Power Connection

869C
869B

120 Vac, 2-wire with ground
240 Vac, 2-wire with ground
2-6

Table 2-3

Model 869C/B Power Controller Specifications (Cont)

AC INPUT(Cont)
AC Connection

869C
Power Cord

and Plug Assy
Plug
Receptacle

DEC

NEMA

Hubbell

7015253
12-11193
12-11194

L5-30P
L5-30R

2611
2610

N/A
N/A

320P6
320R6

869B
Power Cord and

Plug Assy
Plug

Receptacle

7015474

12-14379-03

12-14378-03

CONTROL PARAMETERS
Thermoswitch (exposed to outside
ambient air)
Opens contactorat
Automatically resets at
Controls

71° C (160° F)
49° C (120° F)
Total Shutdown

Input-Signal Current Levels
High
Low

500 vA maximum
10 mA maximum

Input-Signal Voltage Levels
High
Low
Power Control Bus

3to35 V
Oto 1.8 V

Meets DEC Std 123
Pin 1 - Power Request
Pin 2 - Emergency Shutdown
Pin 3 - Ground

Connectors

Female (3)
Male(3)
Air Flow Sensors

DEC 12-09350-03 with DEC 12-09379 pins
DEC 12-09351-03 with DEC 12-09378 pins
Texas Instrument 2SE (DEC 12-14447)

AC OUTPUT

Duplex Receptacles

869C
869B

5 (120 Vac, 20 A; J1-J5)

5 (240 Vac, 15 A; J1-J5)
2-7

Table 2-3

Model 869C/B Power Controller Specifications (Cont)

AC OUTPUT(Cont)
Circuit Breakers

869C
Branch 1 (J2, J4, J5)
Branch2 (J1, J3)

16 A maximumper duplex outlet
16 A maximum per duplexoutlet
(Sum of branches | and 2 not to exceed 24 A)

869B
Branch 1 (J2, J4, J5)
Branch 2 (J1, J3)

12 A maximum perduplex outlet
12 A maximumperduplex outlet
(Sum of branches| and 2 not to exceed 16 A)

Maximum Output Current
869C
869B

16 A per duplex outlet
12 A per duplex outlet

MECHANICAL AND ENVIRONMENTAL
Size
Height

8.18 cm (3.22 in)

Width

48.26 cm (19 in)

Depth

21.20 cm (8.35 in)

Weight

6.75 kg (15 Ib)

Cooling

Convection

Mounting

48.26 cm (19 in) rack

Temperature
Operating
Non-Operating

5° to 50° C (41° to 122° F)
-40° to 66° C (-40° to 151° F)

Humidity

10 to 95% with maximum wet bulb 32° C
(90° F) and minimum dewpoint 2° C (36° F)

Table 2-4

Model 866D/E Power Controller Specifications

INPUT
Voltage
866D
866E

90-132 Vac, 3-phase wye
180-264 Vac, 3-phase wye

2-8

Table 2-4

Model 866D/E Power Controller Specifications (Cont)

INPUT (Cont)
Frequency
866D /E

47 to 63 Hz

Current

866D
866E

24 A maximum at 120 V
12 A maximum at 240 V

Input Power at No Load

866D/E

10 W maximum

Input VA at Full Load

866D/E

8640

Inrush Current

866D
866E

450 A peak for 1/2 cycle at 50 Hz
225 A peak for 1/2 cycle at 50 Hz

Input Overvoltage Transient
(power controller alone)

866D
866E

150 V for 1 s, phase to neutral
300 V for 1 s, phase to neutral

Leakage Current
(power controller alone)
866D/E

1.5 mA at 250 V, 50 Hz

Circuit Breaker

866D
866E

30-30-30-30 A, 4 pole

15-15-15-15 A, 4 pole

Power Cord and Plug

866D
866E

5 wire #10; NEMA L21-30P; Hubbell 2811
5 wire #14; NEMA L22-20P; Hubbell 2521

CONTROL PARAMETERS
Thermoswitch (exposed
to outside ambientair)
Opens contactorat
Auto resets at

71° C (160° F)
49° C (120° F)
2-9

Table 244

Model 866D/E Power Controller Specifications (Cont)

CONTROL PARAMETERS (Cont)
Input Signal Current Levels
High
Low

500 nA maximum
20 mA maximum

Input Signal Voltage Levels
High
Low

+35 V minimum
+1.8 V maximum

Connectors

Female (3)
Male (3)

DEC 12-09350-03 with DEC 12-09379 pins
DEC 12-09351-03 with DEC 12-09378 pins

AC OUTPUT
Duplex Receptacles

866D
866E

5 switched; 2 unswitched; 125 V phase to neutral (20 A, NEMA

5-20R)

5 switched; 2 unswitched; 250 V phase to neutral (15 A, NEMA

6-15R)

Current
Per Duplex Receptacle

866D
866E

16 A peak at 120 Vac, phase to neutral
12 A peak at 240 Vac, phase to neutral

Per Phase

866D
866E

24 A at 120 Vac, phase to neutral
16 at 240 Vac, phase to neutral

Loads

CAUTION

No loads external to the cabinet are to be plugged
into the controller.

MECHANICAL AND ENVIRONMENTAL
Dimensions

Height

Width

Depth

12.7 cm (5 in)
48.6 cm (19.1 in)
20.3 cm (8 in)
2-10

Table 2-4

Model 866D/E Power Controller Specifications (Cont)

MECHANICAL AND ENVIRONMENTAL (Cont)
Weight

12.15 kg (27 lb)

Cooling

Convection

Mounting

48.26 cm (19 in) rack

Temperature

5° to 50° C(41° to 122° F)
-40° to 66° C (-40° to 151° F)

Operating
Non-Operating
Humidity

10 to 95% with maximum wet bulb 32° C (90° F)
and minimum dew point 2° C (36° F)
Table 2-5

Model 861B/C Power Controller Specifications

INPUT
Voltage
861B
861C

180-264 Vac, single phase
90-132 Vac, single phase

Frequency

861B/C

47-63 Hz

Current
861B
861C

16 A at 240 Vac
24 A at 120 Vac

Input Power at No Load

861B/C

10 W maximum

Input VA at Full Load
861B
861C

3840
2880

Inrush Current

861B
861C

225 A peak for 1/2 cycle at 50 Hz

340 A peak for 1/2 cycle at 50 Hz
2-11

Table 2-5

Model 861B/C Power Controller Specifications (Cont)

INPUT (Cont)
Input Overvoltage Transient
(powercontroller alone)

861B
861C

300 V for 1 s, phase to neutral

150 V for 1 s, phase to neutral

Leakage Current
(power controller alone)
861B/C

1.5 mA at 250 V, 50 Hz

Circuit Breaker

861B
861C

20-20-20 A, 3-pole
20-20-30 A, 3-pole

Power Cord and Plug

861B
861C

3 wire #14; NEMA L6-20P; Hubbell 2321
3 wire #12; NEMA L5-30P; Hubbell 261 1

CONTROL PARAMETERS
Thermoswitch (exposed
to outside ambientair)
Opens contactorat
Autoresets at

71° C (160° F)
49° C (120° F)

Input Signal Current Levels
High
Low

500 wA maximum
20 mA maximum

Input Signal Voltage Levels
High
Low

+35 V minimum
+1.8 V maximum

Connectors

Female (3)
Male (3)

DEC 12-09350-03 with DEC 12-09379 pins
DEC 12-09351-03 with DEC 12-09378 pins

AC OUTPUT
Duplex Receptacles
861C

4 switched; 2 unswitched; 125 Vac

861B

4 switched; 2 unswitched; 250 Vac

phase to neutral (20 A NEMA5-20R)
phase to neutral (15 A NEMA6-15R)
2-12

Table 25

Model 861B/C Power Controller Specifications (Cont)

AC OUTPUT(Cont)
Current
Per Duplex Receptacle
861C
861B

16 A peak at 120 Vac phase to neutral
12 A peak at 240 Vac phase to neutral

Per Phase, Maximum
861C
861B

24 A at 120 Vac phase to neutral
16 A at 240 Vac phase to neutral

Loads

CAUTION

No loads external to the cabinet are to be plugged
into the controller.
MECHANICAL AND ENVIRONMENTAL
Dimensions
Height
Width
Depth

12.7 cm (5 in)
48.6 cm (19.1 in)
20.3 cm (8 in)

Weight

4.5 kg (10 Ib)

Cooling

Convection

Mounting

48.26 cm (19 in) rack

Temperature
Operating
Non-Operating

5° to 50° C (41° to 122° F)
—40° to 66° C (-40° to 151° F)

Humidity

10 to 95% with maximum wet bulb 32° C (90° F)
and minimum dew point 2° C (36° F)
Table 2-6

H7100 DC Power Supply Specifications

MECHANICAL AND ENVIRONMENTAL
Dimensions
Width
Height
Depth
Weight

17.8 cm (7 in)
27.9 cm (11 in)
40.6 cm (16 in)
15.9 kg (35 lb)
2-13

Table 2-6

H7100 DC Power Supply Specifications (Cont)

MECHANICAL AND ENVIRONMENTAL (Cont)
Cooling

External forced air at 2.22 m/s (400 linear ft/min)

Temperature
Operating
Storage

5° C (40° F) to 50° C (122° F)
-40° C (40° F) to 65° C (149° F)

Altitude

Operating
Non-Operating

3000 m (10,000 ft) maximum
9100 m (30,000 ft) maximum

ELECTRICAL
Input
Voltage (single phase,
2-wire)

90-128 V, rms
180-256 V, rms

Frequency

47-63 Hz

Current, maximum
At 120 Vac, nominal
At 240 Vac, nominal
Inrush Current

10.0 A, rms
5.0 A, rms

80 A peak maximumfor 1/2 cycle at 128 V rms
or 256 V rms

Power, apparent

1200 VA

Powerfactor

>60% at full load (90-128 V rms)

Input protection

2-pole circuit breaker, 20 A/phase

Output
Power

500 W

Voltage/current

+5.1 V at 10.0 to 100 A (H7100)
+12 V at 1.0to 10 A (H7102 regulator option)
—5.2 V at 3.0 to 30A (H7101 regulator option)
+5.0 V at 2.0 to 20 A (H7103 regulator option)
-5.0 V at 0 to 0.2 A (H7103 regulator option)

Regulation (all dc outputs)

+5%
2-14

Table 2-6

H7100 DC Power Supply Specifications (Cont)

ELECTRICAL (Cont)
Status Indicators

Power normal
Overcurrent
Overvoltage
Powerinverter failure
Plug-In regulatorfailure
Overtem perature

Green LED
Red LED
Red LED
Red LED
Red LED
Reflective Indicator (yellow)

Battery Backup (Optional H7112 Unit)
Duration

10 minutes, minimum

Voltage/current

+5 V at 18.5 A (H7103)
+12 V at 4.6 A (H7102)

-5 V at 0.2 A (H7103)
Table 2-7
1.

BA11-K Mounting Box - DC Power Supply Specifications

120 Vac Input Power - BA11-KE

Parameter

Input power

Specifications
90-132 Vac, 120 Vac nominal

47-63 Hz, single phase

Inrush current

175 A peak for 10 ms maximum at 120 V line voltage

Input power

1200 W maximum at 120 V nominalline voltage

Input current

12 A maximum at 120 Vac

Circuit breaker rating

20 A at 120 Vac

Power factor

Noise Transients

The ratio of input power to apparent power must be greater than

0.85

Single transient 300 V at 0.2 W-s maximum
Single transient, survival: 1000 V at 2.5 W-s maximum
Average transient power survival: 0.5 W maximum

CW Noise

RF field susceptibility

10 kHz-3 MHz: 3 V rms
3 MHz-500 MHz: 1 V rms
500 MHz-1000 MHz: 0.5 V rms

10 kHz-1000 MHz: 1 V/m
2-15

Table 2-7

BA11-K Mounting Box - DC Power Supply Specifications (Cont)

Parameter

Specifications

Power fail

H765 power system is capable of withstanding power interruptions of any magnitude and duration without damage. Storage
time of power supply at low line and full load shall be 20 ms
minimum. Storage time is measured from the time the poweroutage occurs until the time the 5411086 regulator or a regulator unit
(1 through 4) voltage drops below its specified regulation limits.

2. 240 Vac Input Power - BA11-KE
Parameter

Specifications

Input power

180-264 Vac, 240 Vac nominal
47-63 Hz, single phase

Inrush current

80 A peak for 10 ms maximum at 240 Vac line voltage

Input power

1200 W maximum at 240 Vac nominalline voltage

Input current

6 A maximum at 240 Vac

Circuit breaker rating

10 A at 240 Vac

Power factor

The ratio of input power to apparent powershall be greater than

0.85.

Noise
Transients

Single transient, without loss of data: 300 V at 0.2 W-s

Single transient, survival: 1000 V at 2.5 W-s maximum
CW Noise

10 kHz-3 MHz: 3 V rms
3 MHz-50 MHz: 1 V rms
500 MHz-1000 MHz: 0.5 V rms

RF field susceptibility

10 kHz-1000 MHz: 1 V/m

Powerfail

H765 power system is capable of withstanding power interruptions of any magnitude and duration without damage. Storage
time of power supply at low line and full load shall be 20 ms
minimum. Storage time is measured from the time the 5411086
regulator or a regulator unit (1 through 4) voltage drops belowits
specified regulation limits.

2-16

Table 2-7
3.

BA11-K Mounting Box - DC Power Supply Specifications (Cont)

Power-Up and Power-Down Characteristics

Parameter

Specification |

Mounting Box Power Down

5 ms minimum from ACLO._L asserted to DCLO asserted

Mounting Box Power Up

1 ms minimum from +15 V to DCLOL negated
2 ms nominal from DCLO L negated to ACLO L negated

Static Performanceat full load*
Mounting Box Power Down
Mounting Box Power Up

ACLO L drops to LOW: 83-88 Vac
DCLO L drops to LOW: 73-78 Vac
DCLC L goes to HIGH: 75-80 Vac

ACLO goes to HIGH: 85-90 Vac

H765 Regulator Unit Assembly Configurations
Regulator
Unit

Quantity

115

H744
H745
H754

2
l
l

H765-B

230

H744
H745
H754

2
l
l

H765-C

115

H744
H745

2
l

H765-D

230

H744
H745

2
l

70-13323-02

115

H7441
H745
H754 (MOS/core)
H765P

2
l
l
l

70-13323-04

230

H7441
H745
H785 (BBU)*
H765R

2
l
l
l

70-13323-00

115

H7441
H745
H765P

2
l
l

Item

Power System

AC Input

H765-A

*Response to changing ac input (less than 10 V/s).

2-17

Table 2-7

BA11-K Mounting Box - DC Power Supply Specifications (Cont)
Regulator
Unit

Quantity

230

H7441
H745
H765P

2
l
|

70-13323-01

115

H7441
H745
H765P

2
l

70-13323-05

230

H7441
H745

2
l

Item

Power System

AC Input

70-13323-03

H754 (MOS/core)
H765R
5.

Mounting Box Physical and Environmental Characteristics

Item

Description

Chassis size (with H765 power
system and pop panel)

26.52 cm (10.44 in) high
43.48 cm (17.12 in) wide
67.39 cm (26.53 in) deep

Chassis size (with H765 power
system without console panel
and bezel)

26.52 cm (10.44 in) high
43.48 cm (17.12 in) wide
63.50 cm (25 in) deep

Chassis size (without H765
power system, console panel,
and bezel)

26.52 cm (10.44 in) high
43.48 cm (17.12 in) wide
43.82 cm (17.25 in) deep

Expander box chassis weight
(with regulator units and
without system units)

39.47 kg (87 Ib)

H765 power system size

26.37 cm (10.38 in) high
43.48 cm (17.12 in) wide
19.69 cm (7.75 in) deep

Slide extension (three-section
slide)

68.58 cm (27 in) maximum

Slide weight capacity
(box fully extended)

68.04 kg (150 Ib)

3-stop slide

Positions: horizontal, 45° F and 90° F (front panel facing up)

Fan air movementdirection

Horizontally toward rear of chassis
2-18

Table 2-7

BA11-K Mounting Box - DC Power Supply Specifications (Cont)

Item

Description

Moduleslots

22 maximum (2 double system units and | single system unit),
using DIGITAL standard configuration backplanes

Operating temperature range

5° C-50° C

at inlet to box

(41° F-122° F)

Operating humidity

10 to 95% (no condensation)

Cooling efficiency for both fans
at 90 Vac, 50 Hz

Temperature rise no greater than 10° C (18° F)
inlet air temperature to exhaustair.

Table 2-8

H7111 TODC Battery Power Supply Specifications

AC INPUT
Current

0,1 A, maximum rms

Voltage
90-128 Vac, rms
180-256 Vac, rms

H7111A
H7111B

Frequency

47 to 63 Hz

Protection

1/8 A slow-blow fuse

DC OUTPUT
Voltage

+5 Vde £5%

Current

Oto25mA

BAT DCLO
Highstate
Lowstate

Connector

4.0 to 4.5 Vdc

Less than 0.4 Vdc at sink 4 mA maximum

6-pin universal Mate-N-Lok

MECHANICAL AND ENVIRONMENTAL
Dimensions
Height
Width
Depth

8.9 cm (3.5 in)
48.26 cm (19 in)
10.20 cm (4.0 in)

2-19

Table 2-8

H7111 TODC Battery Power Supply Specifications (Cont)

MECHANICAL AND ENVIRONMENTAL (Cont)
Weight

2.25 kg (5 Ib)

Cooling

Convection

Mounting

48.26 cm (19 in) rack

Temperature
Operating

5° to 50° C(41° to 122° F)

Non-Operating

-40° to 66° C (-40° to 151° F)

Humidity

10% to 95% with maximum wet bulb 32° C (90° F)
and minimum dewpoint 2° C (36° F)

Altitude

3000 m (10,000ft)
9000 m (30,000ft)

Operating
Non-Operating
Battery Shelf Life

At 70° C (158° F)
At 0° C (32° F)

40 days, maximum

6000 days, maximum

Battery
Type

Sealed lead-acid (DEC P/N 1212499-00)

Voltage range

10-16 Vdc

Overcurrent protection

2 A fuse

Capacity

5 Ah

Charge time

Less than 24 hr (90% charge)

Operating time

100 hr, minimum

Table 2-9

H7112 Memory Battery Backup Power Supply Specifications

AC INPUT
Voltage
Range

Voltage
Nominal

90-128 Vac
180-256 Vac
90-128 Vac
180-256 Vac

120 Vac
240 Vac
120 Vac
240 Vac

Frequency

Current

60 Hz +1 Hz

60 Hz +1 Hz
50 Hz +1 Hz

50 Hz +1 Hz

2-20

1.0 A, maximum

0.5 A, maximum
1.0 A, maximum

0.5 A, maximum

Table 2-9

H7112 Memory Battery Backup Power Supply Specifications (Cont)

AC INPUT(Cont)
Charge Time (90% charge)

16 hr, maximum

Input protection

120 Vac

240 Vac

1.0 A slow-blow fuse

0.5 A slow-blow fuse

DC OUTPUT
Voltage

27-45 Vdc

Power

250 W (constant powerload)

Battery Holdup Time

10 minutes, minimum

INPUT SIGNALS
Regulator input voltage

30 Vde

AC OK voltage

-~12 +3 Vdc

Closure

J7-3 to J7-6

BATTERIES(3 in series)
Type

Sealed lead-acid (DEC P/N 1212499-00)

Voltage range

30-48 Vdc

Overcurrent protection

15 A fuse

Powerrequired

280 W

ENVIRONMENTAL AND PHYSICAL
Dimensions
Height
13.2 cm (5.2 in)
Width
48 .26 cm (19.0 in)
Depth
13.64 cm (6.16 in)
Weight

11.25 kg (25 lb), approximately

Cooling

Convection

Mounting

48.26 cm (19 in) rack

Temperature
Operating
Non-Operating

5° to 50° C (41° to 122° F)
—40° to 66° F (-40° to 151° F)

2-21

Table 2-9

H7112 Memory Battery Backup Power Supply Specifications (Cont)

ENVIRONMENTAL AND PHYSICAL(Cont)
Humidity

10 to 95% with maximum wet bulb 32° C (90° F)
and minimum dew point 2° C (36° F).

Altitude
Operating
Non-Operating

3000 m (10,000 ft)
9100 m (30,000ft)

Battery Shelf Life*
At 70° C (158° F)

40 days, maximum

At 0° C (32° F)

_ 6000 days, maximum

Connectors and Cables

Two 3-pin (J10, J11)
AC input cable
BATTERY OUTinterface cable
Twobindingposts for external battery

*Shelf life is linear between these extremes.

2-22

CHAPTER 3
POWER SYSTEM DESCRIPTION

This chapter discusses the VAX-11/780 Power System under the following basic headings:
1.

Physical configuration (includes a brief description and illustrations showing relationships
between power system and other system elements)

AC powerdistribution

DC power generation and distribution

Power failure provisions (e.g., power-fail sequencing, battery backup power supplies, and
power supply status displays)

Cabling.

In overview, power distribution within the system is not complicated. Each cabinet powercontroller
receives its 3-phase or single-phase primary powerdirectly from an individual customer-supplied receptacle. The controller then distributes this power throughout its cabinet, providing 120 Vac or 240
Vac to the individual loads (e.g., dc power supplies, fans, microcomputer, floppy disk, air flow interface, etc.).
In the main cabinet (refer to Paragraph 3.1) the microcomputer and floppy disk have their owninternal power supplies. The dc power supplies provide +5.1, -5.2 and +12 regulated outputs for the
numerous modules in the CPU, UBA, memory, MBA, and FPA. Theair flow interface (used with the
866 controllers only) provides +15 Vdc for the air flow sensors. In the 869 controllers this voltage is
provided by circuits in the unit.
All cabinets in the VAX-11/780 (main cabinet, expander cabinet(s), and tape drive cabinets) are powered up and down via the DEC powercontrol bus that interconnects them. However, system standalone peripherals operate autonomously. Although an emergency shutdownsignal on the control bus
shuts down those devices operating off “‘switched”’ controller outlets, the units (e.g., memory power
supply, memory powersupply fan, andair flow interface) on “‘unswitched”’ receptacles will continue to
operate until the controller’s main circuit breaker can be manually set to OFF. This restriction does
not apply to the more advanced 869 series controllers, whose main circuit breaker incorporatesa trip
coil permitting total shutdown of both switched and unswitched power. Details of 869 operation are
discussed in the following sections.
Centralized control of power distribution initiates at a key-operated switch at the right end of the main
cabinet control panel (refer to Figure 3-1).
3-1

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3.1 PHYSICAL CONFIGURATION
The basic VAX 11/780 computer system comprises (refer to Figure 3-2):
1.

A 1.5 m (5 ft) tall, 1.2 m (4 ft) wide (double-width) highboy central processor unit (CPU)
cabinet

A 1.5 m (5 ft) tall, 0.6 m (2.2 ft) wide (single-width) highboy Unibus expansion cabinet

Storage devices (e.g., tapes, disks, etc.)

LA36 DECwriter II console terminal.

3.1.1 Main Cabinet
The main cabinet houses the following basic equipment:
l.

Central processor unit (KA780)

256K-byte MOS memory (MS780)

Unibus adapter (DW780)

Two powersupplies for the CPU

One power supply for the memory

Three cooling blowers

Time-of-day clock battery power supply

11/03 microcomputer

RXO1 floppy disk subsystem

10.

869 or 866 3-phase power controller (located behind the RXO1 in Figure 3-2).

In addition, the main cabinet provides space for the following optional equipment:
1.

FP780-AA(AB) high-performancefloating-point accelerator.

Writable Control Store (WCS) of 1K locations (KU780)

Upto 4 megabytes of ECC MOS memory

Two Massbus adapters (RH780)

Power supply for floating-point option

Power supply for Massbus option

Memory battery backup power supply option.

3-3

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3-4

3.1.2 Unibus Expansion Cabinet
The Unibus expansion cabinet is an integral component of all VAX-11/780 systems. It houses a maximum of two BAI1-K mounting boxes, (each with integral power supply) and provides spaceto accommodatethree distribution panels for handling a total of up to 48 asynchronous multiplex lines.
At installation, the expansion cabinet is physically mated to the main cabinet or, the model H9602
expansion cabinet (if used).
3.1.3 VAX-11/780 Expansion Cabinet (H9602-HA/HB)
The VAX-11/780 expansion (SBI) cabinet (refer to Figure 3-3) is a single-width highboy having the
same dimensions as the Unibus expansion cabinet. When used, it is physically mated with the main

cabinetat its left end and the Unibus expansion cabinetat its right end. The H9602-HA/HB provides
mounting space for:
1.

Up to one million bytes of expansion memory with memory control

Two Massbus adapters (RH780)

One memorybattery backup option (H7112-A/B)

Power supply for the memory

Power supply for the MBAs.

To expand the VAX-11/780 system beyond the limits of the Unibus expansion cabinet shown in
Figure 3-2, an add-on Unibus expansion cabinet (H9602-DF/DH) is available. Figure 3-3 showsthe

space allocations of the Unibus add-on expansion cabinet and the VAX-11/780 H9602-HA/HB ex-

pansion cabinet as seen from the front. Figure 3-4 is a top view of the BA11-K extension mounting box
used with the Unibus expansion cabinet and the add-on Unibus expansion cabinet. Shown in this
figure are the DD11-DK peripheral mounting panel, DZ11-A asynchronous multiplexer for the video
terminals (e.g., VI'52s) used in some configurations, and the RK611 controller (five boards and backplane) for the RK06 disk drives. Figures 3-5 and 3-6 show the configuration of the mounting box and
its power supply, respectively.
The RK611 and DD11-DK each occupy 2 SUs (system units) of space and provide a total of 8 hex
slots and 3 quad slots of additional mounting space.

Figures 3-7 and 3-8 showfront and rear exterior views of the 11/780-C main cabinet, respectively.

Accompanying sheets for each figure give cabling data.

For details of the BA11-K extension mounting box,refer to the BA/1-K Mounting Box Manual (DEC11-HBKEF-A-D)included in the documentation package for VAX-11/780 systems.

3.2 AC POWER DISTRIBUTION
In VAX-11/780 systems delivered after June 1978, the 866 3-phase controllers are replaced by more
versatile equivalents of the new 869 series. To simplify the discussion on ac powerdistribution, it
should be pointed out that all of these DEC standard powercontrollers (refer to Tables 3-1 and 3-2)
have similarities. Figure 3-9 shows their commonbasic concept.

3-5

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(REAR MOUNTED)

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oon, Y
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POWER

PANEL SPACE FOR
BA11-K #4

cCerl/ eo

SUPPLY
FOR MBAs

COOLING

PANEL SPACE FOR
BA11-K #3

MEMORY BATTERY BACKUP OPTION
THREE-PHASE
PWR. CONTROLLER

SINGLE-PHASE
PWR. CONTROLLER

VAX -11/780 EXPANSION CABINET

UNIBUS EXPANSION CABINET

(SBI CABINET)
(H9602-HA/HB)

(H9602-DE)

Figure 3-3 Equipment Space Allocation in Add-On Cabinets (Front View)

3-6

MLILLLLLLLL
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TK-0436

Figure 3-4 Space Allocation for DZ11-A Multiplexer
and RK611 Controller in BA11-K Mounting Box

3-7

H765 POWER SUPPLY ASSEMBLY

—

CARD GUIDE

BOX

TRANSFORMER
ASSEMBLY

REGULATOR #3
(H744/H7441)

|
LOGIC
BACKPLANE

REGULATOR #4

: (H754)

POWER DISTRIBUTION
BOARD

REGULATOR #2 X<(|

(H744/H7441)
REGULATOR ON
(H745)

AIR
VENTS

AC INPUT BOX (5413089 POWER

CONTROL BOARD AND
5411086 REGULATOR ARE
INTERNAL TO THE AC INPUT BOX)
TK-0483

Figure 3-5

BA11-K 10.5 Inch Mounting Box

3-8

H745 REGULATOR #1 ASSY.
(NOT VISIBLE BELOW)
H754/H785

|
REGULATOR #4 assy. 11744/H7441
REGULATOR #3ASSY.

AC INPUT BOX ASSY.

H744/H7441
REGULATOR #2 ASSY.

TK-0482

Figure 3-6

H765 Power Supply Assembly

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3-10

11780 CA/DA 115 V.A.C 60HZ SYSTEM
(REE. ONLY)

PART NO.

7014323-06

DESCRIPTION

FROM

|POWER CORD ASSY(FAN 115 V)} CORD-P1
-P2

7014323-06

|POWER CORD ASSY(FAN 115 V)| CORD-P1
-P2

7014323-06

|}POWER CORD ASSY(FAN 115 V)} CORD-P1
-P2

.9107673-09

EXTENSION CORD 115V 15A

CORD-PLUG
-JACK

9107673-06

EXTENSION CORD 115V 15A

CORD-PLUG
-JACK

TO
866-D J9-A
BLOWER #1 J1
866-D J15-A
BLOWER #2 J1
866-D J10-8
BLOWER #3 J1
866-D J10-A
P.S. #2-AC
866-D J14-A
P.S.#4-AC

9107673-06

EXTENSION CORD 115V 15A

CORD-PLUG

866-D J9-B

-JACK

P.S. #5-AC

9107673-09

EXTENSION CORD 115V 15A

CORD-PLUG
-JACK

9107673-09

EXTENSION CORD 115V 15A

CORD-PLUG

866-DJ12-A
P.S. #3-AC
866-D J11-A

-JACK

P.S. #1-AC

AIRFLOW SENSOR BOX

AC CORD-PLUG

866-D J11-B

7015036-00

H7111-A

T.O.D BATTERY

AC CORD-PLUG

866-D J15-B

H7112-A

MEMORY BATTERY

AC CORD-PLUG

866-D J14-B

PDP11/03 AA

16 BIT COMPUTER

AC CORD-PLUG

866-D J13-B

RX01-FA

RX01 FLOPPY U.A.

AC CORD-PLUG

RX01 RELAY-J1

9107673-03

EXTENSION CORD 115V 15A

CORD-PLUG

866-D J13-A

7013928-00

FAN ASSY 115V

-JACK

RXO1 RELAY-P1

AC CORD-PLUG

866-D J12-B
TK-0486

Figure 3-7

VAX-11/780-C/D Main Cabinet (Cabling Data) (Sheet 2 of 3)

3-11

FOR 11780-C/D
ITEM NO.
REF
ONLY

PART OF
KC780 |

DESCRIPTION

FROM

1
2

7014213-OK |CABLE, OVER TEMP.
7014213-0K CABLE, OVER TEMP.

PS #2-J4
PS #3-J5

PS #3-J4
PS #4-J5

KA780-J20

FOR 11780-C
7014213-4A CABLE, OVER TEMP.
7014213-3E CABLE, OVER TEMP.

PS #4-J4
N.C.

5
6
7

PART OF
KC780 ASSY

8
9
|
|
12
,
11

866-J1
PS #2-J5

SCP-J1
KA780-J19
scPu3
BNO
SCP-J2
KA780-J7
KA780-J8

FOR 11780-C WITH H7112
7014213-4A CABLE, OVER TEMP.
866-J1
PS #4-J4
7014213-3E CABLE, OVER TEMP.
H7112-J1 PS#2-J5
CABLE-P2 H711247
7014547-3D |CABLE, BATTERY OPTION CABLE-P1 PS #4-BATT.
ADAPT.

12.
14.
13.

FOR 11780-C WITH FP780
7014213-4A |CABLE, OVER TEMP.
866-J1
7014213-0K |CABLE, OVER TEMP.
PS #1-J4
7014213-3E |CABLE, OVER TEMP.
PS #1-J5

12.

FOR 11780-C WITH H7112 & FP780
17014213-4A CABLE, OVER TEMP.
866-J1

13.
14.

|7014213-3E
|7014213-0K

10.

|7014547-3D

12
1

OPTIONAL ~

PART NO.

CABLE, OVER TEMP.
CABLE, OVER TEMP.

H7112-J1
PS#1-J4
CABLE, BATTERY OPTIONL< ABLE-P2
CABLE-P1

PS #4-J4
PS #2-J5
N.C.
|PS#4-J4
PS #1-J5
|PS#2-J5
[H7112-J7
ie)
[PS #4 BATT. ADAPT.

NOTE: * CONN. J8 ON ADAPTER CABLE (7015155) SNAPS
INTO CUTOUT ON EXPANDER 1|/D CONN. PANEL.

Figure 3-7

VAX-11/780-C/D Main Cabinet (Cabling Data) (Sheet 3 of 3)
3-12

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3-13

11780 CC/DC 115VAC 50 HZ SYSTEM

RE ONLY)

PART NO.
7014323-06

;

7014323-06

DESCRIPTION

FROM

POWER CORD ASSY(FAN 115V)| CORD-P1
-P2
POWER CORD ASSY(FAN 115V)| CORD-P1
:

-P2

TO
866-D J9-A
BLOWER #1 J1
866-D J15-A

BLOWER #2 J1

10
1
12
13
1A

H7111-A
T.0.D. BATTERY
H7112-A
MEMORY BATTERY
PDP 11/03-AA 16 BIT COMPUTER
RXO1-FC
RXO1 FLOPPY UA.
9107673-03 ]|EXTENSION CORD 115V15A

AC CORD-PLUG |
AC CORD-PLUG
AC CORD-PLUG
CORD-PLUG
|CORD-JACK

7013928-00

AC CORD-PLUG 866-D J12-B

3
,
°
6
’
;

FAN ASSY 115V

866-D J15-B
866-D J13-B
RXO1 RELAY-J1
866-DJ13-A
RXO1 RELAY-P1

TK-0537

Figure 3-8

VAX-11/780-C/D Main Cabinet (Cabling Data) (Sheet 2 of 3)

3-14

FOR 11780-D

ITEM NO.
REF ONLY

PART NO.

DESCRIPTION

FROM

"16
15
11

7014213-0K
7014213-4A
7014213-3E

CABLE, OVER TEMP.
CABLE,OVERTEMP.
CABLE, OVER TEMP.

PS #4-J4
866-J1
PS #2-J5

PS #5-J4
PS #5-J5
N.C.

16
15
11

FOR 11780-D WITH H7112
7014213-0K |CABLE, OVER TEMP.
PS#4-J4
7014213-4A |CABLE, OVER TEMP.
866-J1
7014213-3E |CABLE, OVER TEMP.
PS #2-J5

7014547-3D |CABLE, BATTERY OPTION| CABLEP2 [H7112-J7
CABLE-P1 PS #4 BATT. ADAPT.

16
15
13
14

7014213-0K
7014213-4A
7014213-3E
7014213-0K

16
15
13
14

FOR 11780-D WITH H7112 & FP780
7014213-OK CABLE, OVER TEMP.
PS#4-J4
7014213-4A |CABLE, OVER TEMP.
866-J1
7014213-3E CABLE, OVER TEMP.
H7112-J1
PS #1-J4
7014213-0K CABLE, OVER TEMP.

7014547-3D |CABLE, BATTERY OPTION

FOR 11780-D WITH FP780
CABLE,OVERTEMP.
PS#4-J4
CABLE,OVERTEMP.
866-J1
CABLE,OVERTEMP.
PS#1-J5
CABLE,OVERTEMP.
PS#1-J4

FROM

NO.

PARTNO

7014320

17
17
19.
19
19
19
19
19

PS#5-J4
PS #5-J5
1H7112-J1

7015155

CABLE-P2

PS #6-J4
PS #5-J5
N.C.
PS #2-J5
|PS #5-J4
|PS #5-J5
[ps #1-J5
|PS #2-J5
|H7112-J7

CABLE-P1 |PS #4 BATT. ADAPT.

INTERCONNECTION TABLE FOR 11780-C/D

DESCRIPTION
AIRFLOW SENSOR #3

AIRFLOW SENSOR #2
AIRFLOW SENSOR #1
AIRFLOW ADAPTERCABLE|

CONN NO.
P1

P1
Pi
J1
j2
P3
Ja
Pi
P2

18
18
18
18
20
24
22
22

PART NO.

DESCRIPTION

CONN

7014319

AIRFLOW SENSE HARN.

866-D/E

PWRCONTROL BOX
I/O CONNECTOR PANEL
AIRFLOW SENSOR BOX

7015036

J4
J5
Py
P2
J2
«
J3
J4

TK-0505

Figure 3-8

VAX-11 /780-C/D Mair: Cabinet (Cabling Data) (Sheet 3 of 3)
3-15

Table 3-1
Type

Voltage

869B

Standard DEC Power Controllers Used in VAX-11/780 Systems

| Frequency (Hz)

Phase(s)

A/Phase

CB Poles

Max. Load kVA

240

47-63

Single

3.83

869C

120

47-63

Single

2.88

869D

120/208

47-63

Three

8.64

869E

240/416

47—63

Three

8.64

866D

120/208

47—63

Three

8.64

866E

240/416

47-63

Three

8.64

861B

240

47—63

Single

3.83

861C

120

47—63

Single

2.87

3-16

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3-18

3.2.1. Power Control Bus
Powercontrollers interconnected by the power control bus accomplish the following basic functions.
1.

Control of large amounts of power by control signals of relatively low powerlevel.

Convenient distribution of primary power to controlled devices.

Filtering of all primary powerto protect data from noise effects.

Automatic removal of primary powerin the event of overload or overtemperature conditions.

Isolation of portions of the power distribution system to permit servicing of \discrete areas
without interrupting total system operation.

The power controlbusis a series of 3-wire cables harnessed for interconnection of all power controllers
in the central processor cabinet array. Parallel-wired 3-pin Mate-N-Lok connectorsat the rear of each

controller (refer to J4, JS, and J6 in Figure 3-15) are used to interconnect the controllers and the main

cabinet control panel (refer to Figure 3-1). The operation of the power control busis as follows.
1.

Connection of line 1 (POWER REQUEST) to line 3 (ground) energizes the contactor
through the pilot control board to cause ac power to be applied to the switched outlets.
Wheneverthe controller's LOCAL/OFF/REMOTEswitch (Figure 3-12) is in its LOCAL
position, lines 1 and 3 are connected.

Connection of line 2 (EMERGENCY SHUTDOWN)to line 3 (ground) causes disconnect
of all power to the controller’s switched outlets.

3.2.2 AC Power Distribution with 866 and 861 Power Controllers
Figure 3-10 is a single-line diagram showing the ac power distribution for VAX-11/780 systems in
which the central processor cabinets (main cabinet, expandercabinets, tape drive cabinets) use the 866
3-phase and 861 single-phase controllers. The 866D is for 120/208 Vac, 47-63 Hz primary power and
the 866E for 240/416 Vac, 47-63 Hz. The 861C operates off single-phase 120 Vac and the 861 B off 240
Vac primary power.
In the figure, note that the controller receptacles (J9 through J15) are the outlets shown on the rearview drawing of the 866 (Figure 3-21). Receptacle numbers and locations are identical on both the
866D and 866E; however, the polarization for the 866D outlets is 120 Vac and 866E is 240 Vac.
As shown in the diagram, the unswitched phase provides ac powerto: the H7112 Battery Backup
Power Supply option at J14B, the No. 4 power supply feeding dc voltages to the MS780A memoryat
J14A, the H7111 Time-of-Day Clock Battery Backup power supply at JI15B, and the No. 2 blower
(located above the memory dc power supply) at JI5A.
The devices on the unswitched phase continue to operate in the 866/861 controller configuration even
after EMERGENCY SHUTDOWNhas been commanded on the power control bus.
The expander cabinet configuration is only one of several possible combinations, but the basic intercontroller relationship still holds.
Also physically situated outside the controller block are the power supply thermal sensors; each supply
has a single thermal sensorlocated on its output transistor heat sink. The main cabinet air flow sensors
(3 in the VAX-11/780 main cabinet) are located just below the card cage in the narrow space separating the bottom of the cage from the tops of the power supplies. Seen from the front or rear of the

3-19

cabinet, each sensor is located above one of the three blowers. These locations provide optimum
sensing of air velocity and temperature as the downward flow of cooling air leaves the modules in the
card cage.
Note that the primary powercontrol originates at the key-operated switch on the control panel of the
main cabinet, passes through the pilot control circuit, and energizes or deenergizes the contactor
controlling the primary power flow to the ‘“‘switched”’ receptacles. Figure 3-11 shows the ac power
distribution details for the 3-phase, 120 Vac, 60 Hz system. Similar drawings for the 3-phase 120 Vac
and 240 Vac, 50 Hz systems are included in the printset.
AC powerdistribution in each controller follows this basic sequence:
1.

A 3-phaseline filter removes high frequency components entering the system via the primary

power source.

An indicating lamp in eachhotleg of the 3-phase supply illuminates when the powerplug of
the power controller is plugged into the customer’s receptacle.

A 3-phase circuit breaker applies power to the unswitched outlets or, as in the case of the
869D, which hasan individual circuit breaker for each duplex outlet, to the outlet CBs. This

power is also applied to the input contacts of the 3-phase contactor.
4.

Whenthe contactor is energized (closed) by command from the control board, poweris also
applied to the individual outlet CBs grouped under the heading of “‘switched”’ outlets.

With all outlet CBs in the closed position, single phase 120 Vac (869D controller) or 240 Vac
(869E controller) is applied to the equipment plugged into the receptacles of the power
controller.

Since the power controllers of the main cabinet and expansion cabinet are interconnected
via the DEC powercontrol bus, the equipmentin all other central processor cabinets comes
on at the same time as the equipment in the main cabinet to render the system operational.
Peripherals are individually supplied with primary power from customer receptacles, and
are manually switched on.
NOTE
The 869 controller provides an optional 1/2 second
turn-on delay before any power-up or power-down
commandis transmitted to the next cabinet.

3.2.3. AC Power Distribution of Systems Using 869 3-Phase and Single Phase Power Controllers
Figure 3-12 1s a single-line diagram showing the ac power distribution for VAX-11/780 systemsin
which the central processor cabinets use the 869-series 3-phase and single-phase controllers. The 869 D
is for 120/208 Vac, 47-63 Hz primary power; 1.e., is the conterpart of the 866D. Similarly, the 869E is
the counterpart of the 240/416 Vac, 47-63 Hz 866E. Figure 3-13 is a simplified block diagram of the
869 family of controllers, while Figures 3-14 through 3-28 (exclusive of Figure 3-22, the Air Flow
Interface) show the front and rear features of the 869, 866 and 861 controllers. Since the 861s do not
have rear receptacles, only their front views are shown.
The 869C (Figure 3-23) corresponds to the 120 Vac, 47-63 Hz, single phase 861C (Figure 3-27) and the
869B (Figure 3-25) correspondsto the 230 Vac, 47-63 Hz, 861 B single-phase controller (Figure 3-28).

3-20

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3- PHASE POWER CONTROLLER IN CPU CABINET (CONT.)

PHASE 1 SWITCHED

PDP-11/03
MICROCOMPUTER

FLOPPY
DISK RELAY
ASSY.

PHASE 2 SWITCHED
J12B

J12A

P.S.#3
FOR

AIR FLOW
SENSOR

CPU,WCS

ASSY.

J10A

psn

BLOWER #3

@™

@®z

+15VDC

Ps.

J9A

BLOWER #1

RH780

+5.1V @ 40A
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FOR MBA

CPU,UBA
(DW780)

+5.1V @ 30A (H7100)
-5.2 V@ 10A (H7101)
GE

ACCELERATOR
FP-780A

J10B

FOR
;
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P.S.

+5.1V @ 70A
(H7100)

J1I1A

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P.S.#1

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ELOPPY
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J11B

OPTION
+5.1V @ 35A
(H7 100)
aD

Ez a

ea»

VAX-11/780 3-PHASE
CONTROLLER OPTIONS

H7100 POWER SUPPLY
OPTIONS

H7100 REGULATED-DC
OUTPUT OPTIONS

866-D 120/208V., 3¢, 5W, 50/60 Hz, 24A/%, 30A CB
866-E 240/416V., 34, 5W, 50/60 Hz, 12A/¢, 15A CB

H7100A 120V, 50/60 Hz
H7100B 240V, 50/60 Hz

H7100 (BASIC): +5.1V @ 10 TO 100A
H7101: -5.2V @ 3 TO 30A

H7102: +12V @ 1 TO 10A
_f +5V @ 20 TO 20A
H7103: sv -0TO 0.2A

TK-0459

Figure 3-10 VAX-11/780 AC Power Distribution System Using the 866 (3-Phase) and
861 (Single-Phase) Power Controllers (Sheet 2 of 2)

3-22

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P.S. #4
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MEMORY

BLOWER #2

H7100 REGULATED-DC
OUTPUT OPTIONS

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H7101: -5.2V @3 TO 30A
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H7103:
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J14A

CONTROLLER OPTIONS
869-D 120/208V., 30, 5W, 50/60 Hz, 244/0, 30A CB
869-E 240/416V., 30, 5W, 50/60 Hz, 12A/0,15ACB

PHASE 1 SWITCHED

PDP11/03
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TK-0843

Figure 3-12
VAX-11/780 AC PowerDistribution System
Using the 869 3-Phase Power Controller (Sheet 2 of 2)
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Figure 3-19 866D Power Controller (Rear View)

Figure 3-18 866D Power Controller (Front View)

TK-0448

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3-34

Table 3-3 comparesthe 869D and 866D 120/208 Vac 3-phase controllers in terms of front-panel, backpanel, and interior features (Figures 3-14 through 3-21). The significant differences are as follows.
1.

The 869D uses a main (3-phase) circuit breaker having inrush protection and a trip coil that
permits shutdownof primary powerto the controller’s unswitched receptacles in response to
a signal from theair flow sensor located above the memory powersupply, or total shutdown
in response to an overtemperature signal from a sensor in the controller, or from the overtemperature sensor in anyof the powersupplies. The 866D hasneither a trip coil nor inrush
protection, but both controllers can effect shutdown of receptacles on switched power.

The 869D has one more switched duplex outlet and one more unswitched duplex outlet than
the 866D; specifically, the 869 has 3 switched outlets per phase, one unswitched and two
switched.

The 869 provides a +15 Vdc output energizing up to 5 air flow sensors(only 3 are used in the
VAX-11/780 main cabinets), thus eliminating the need for the +15 Vdc provided bytheair
flow interface (Figure 3-22) provided with each 866 controller.

The 869 provides an individual front-panel circuit breaker for each duplex receptacle, to
enable manual disconnect of any device receiving power from this controller.

The pilot control board of the 869 replaces the reed relay and Triac combination (used for
contactor control in the 866) with a solid-state switch. This board also includesdelay circuitry which, if desired, powers up or down a second controller 1/2 second after receipt of a
POWER REQUEST or EMERGENCY SHUTDOWNcommand via the power control
bus.

A rear view comparison of the 869 and 866 powercontrollers (Figures 3-15 and 3-19) shows that both
controllers have three (parallel-wired) connectors for the DEC powercontrol bus; viz., J4, J5, and J6
on the 869 and Jl, J2, and J3 on the 866. The 866 has no other control connectors.
The 869 controllers, because of their more extensive controlflexibility, have four additional connectors

(J7, J8, J9, and J10). These connectors are discussed briefly below (but not in the order named).

Switched Power Shutdown (Connector J8)
Closure of either air flow sensor for the switched fans (Figure 3-10, blowers | and 3), or any low (Table
2-2 under heading of “Input Signal Voltage Levels’) from pin 2 to pin | of J8 on the back of the 869
powercontroller (Figure 3-15) will cause power to the switched outlets to be removed without energizing the emergency shutdown that occurs when an overtemperature signal appears on the DEC power
bus. However, logic levels for a switched power shutdown via J8 must conform with those for the DEC
power bus. Pin connections for J8 are as follows.
4
3
2
l

NC
+15 Vdc switched
Switched shutdown
Ground

3-35

Table 3-3

Comparison of 869D and 866D 3-Phase Power Controllers

FRONT PANEL
869 Controller

866 Controller

3-phasefilter with
cover and inputstuds

Yes

Phase lamps(3)

Yes

Transformerfuses(3)

Yes

LOCAL/OFF/REMOTEswitch

Yes (rotarysel)

Yes (toggle)

Main circuit breaker control

Yes (4-pole)

Phase circuit breaker control

Yes (three 4-pole)

Output receptacle CBs
(1 per duplex receptacle)

Yes (9)

Switched

Unswitched

Power control bus

J4, J5, J6

J1, J2, J3

Delay out

Switched shutdown

Total shutdown

Unswitched shutdown

J10

Main CB

Yes (with trip coil and
inrush protection)

Yes (withouttrip coil
or inrush protection)

Contactor

Yes

Pilot control board

Yes

Pilot control transformer

Yes (3-phase)

Yes (single phase)

REAR PANEL
Output receptacles, duplex

Connectors

INTERIORS

3-36

Total Power Shutdown (Connectors J9 and J10)
Any low (Table 2-2) from pin 2 to pin 1 on J9 and J10 at the rear of 869 power controller will cause the
main circuit breaker to trip, interrupting both the switched and unswitched power to output receptacles. Emergency shutdown on the DEC powercontrol bus will be asserted. Logic levels must conform to those established for the DEC power bus. Pin connections for J9 and J10 are as follows.
2
bo,

m Nw

Ji0

Total shutdown
Ground

+15 Vdc unswitched

NC
Unswitched (total) shutdown
Ground

Air Flow Sensing (Connectors J8 and J10)
The controller is designed to interface with air flow sensor 12-14447 (TI-2SE). These barium-titanate
SCR-switched sensors use the +15 Vdc supplied by connectors J8 and J10 (Figure 3-15). A maximum
of five air flow sensors can be accommodated: three on switched +15 Vdc and two on unswitched +15
Vdc. Figure 3-32, the controller block diagram, showsthe circuit relationships.
Cabinet Power-up Sequencing (Connector J7)
Connector J7 provides an output(at pin 1) for a 1/2 second delay in sequencing a second cabineton, in
response to a power-up request. If an 869 controller is used in the second cabinet, that 869 will provide
another half second delay between the powering up of its cabinet and a third cabinet, etc.
Figures 3-29, 3-30, and 3-31 are matrices showing the effects of five input conditions at the controller

on the three output conditions. Figure 3-29 showsthese effects when the REMOTE/OFF/LOCAL

(ModeSelector) switch on the front panelof the 869 is set to LOCAL MODE. Figures 3-30 and 3-31
show similar effects for the other two switch settings; 1.e.. OFF and REMOTE.
As shown, the five input variables are:
Main circuit breaker (CB1)

Power request (via J4, J5, or J6 - DEC power control bus)

Emergency shutdown (via J4, J5, or J6)
Switched shutdown(via J8)
Total shutdown (via J9) or unswitched shutdown (via J10).
The three output variables are:

Delayed power request
Switched power to outlets (J12, J13, J15, J16, J18, and J19)
Unswitched powerto outlets (J11, J14, and J17).
Possible input states are identified in the legend. Asis seen in Figures 3-29 and 3-30 the outputs for any
given set of input conditions(e.g., condition 1) will be the same regardless of the ON or OFF state of
the power request, as indicated by the column of Xs. In Figure 3-30, the Ys under heading of Delayed
Power Request indicates that the OFF or ONstate of this output is the same as that of the power

request input for that condition. For example, in condition 4, if the power request state is ON and the
other input conditionsare as listed for this OFF modeof the selector switch, then the delayed poweris
ON and a 1/2 second delay will occur in the powering up of successive cabinets.

3-37

INPUT CONDITIONS

OUTPUT CONDITIONS

MAIN CIRCUIT BREAKER

DELAYED POWER REQUEST

POWER REQUEST

SWITCHED POWER TO OUTLETS

EMERGENCY SHUTDOWN

UNSWITCHED POWER TO OUTLETS

SWITCHED SHUTDOWN
UNSWITCHED
(TOTAL) SHUTDOWN

OFF

CONDITION 1

OFF

CONDITION 2

OFF

CONDITION 3

OFF

CONDITION 4

OFF

CONDITION 5

OFF

OFF]

LEGEND:
ON = TRUE
OFF = FALSE

X = EITHER ON OR OFF
Y = SAME ON OR OFFSTATEAS X (POWER REQUEST) FOR THAT CONDITION
TK-0444

Figure 3-29

869 Power Controller Input/Output Relationships — LOCAL ON Mode

3-38

INPUT CONDITIONS

OUTPUT CONDITIONS

MAIN CIRCUIT BREAKER

DELAYED POWER REQUEST

POWER REQUEST

SWITCHED POWER TO OUTLETS

EMERGENCY SHUTDOWN

UNSWITCHED POWER TO OUTLETS

SWITCHED SHUTDOWN
UNSWITCHED
(TOTAL) SHUTDOWN

OFF

OFF]

OFF

CONDITION 1

OFF

CONDITION 2

OFF

CONDITION 3

OFF;

OFF

CONDITION 4

OFF

CONDITION 5

OFF

ON
ore

OFF

OFF
ore

CONDITION N |

OFF

OFF FF

OFF

|on

TK-0443

Figure 3-30

869 Power Controller Input/Output Relationships — OFF Mode

3-39

INPUT CONDITIONS

OUTPUT CONDITIONS

MAIN CIRCUIT BREAKER

DELAYED POWER REQUEST
SWITCHED POWER TO OUTLETS

POWER REQUEST
EMERGENCY SHUTDOWN

UNSWITCHED POWER TO OUTLETS

SWITCHED SHUTDOWN
UNSWITCHED
(TOTAL) SHUTDOWN

OFF OFF

OFF

CONDITION1

OFF

OFF OFF

off

OFF OFF OFF

CONDITION2

ofr OFF

oFF

OFF OFF

CONDITION3

off

ore

conpitiona

oFe|

oFF

OFF]

CONDITIONS

OFF

CONDITION6

OFF

CONDITION7

OFF

ON
TK-0442

Figure 3-31

869 Power Controller Input/Output Relationships — REMOTE Mode

3-40

Note that in Figure 3-29, condition 5 has twodiscrete sets of input conditions that result in a single set
of output conditions. A similar situation exists in condition 6 of Figures 3-30 and 3-31.
3.2.4 Controller Functional Descriptions
This section provides a detailed functional description of the 869 and 866 controllers used in VAX-

11/780 systems. Table 3-1 lists the standard DEC controllers available for these systems.

3.2.4.1

869 Controllers - The 869 controllers used in VAX-11/780 systemsare:

869D - 120/208 Vac, 3-phase
869E — 240/416 Vac, 3-phase
869C - 120 Vac, single phase
869B - 240 Vac,single phase.

869D Controller (3-Phase, 120/208 V)
Figure 3-32 is a block diagram of the 869D controller. The 120/208 Vac is customer provided from a 3phase source to a DEC 12-12315 receptacle (NEMA L21-30R; Hubbell 2810). A 4.5 m (15 ft) 5-wire
power cord with #10 conductors connects the five 10-32 ac input studs at the right front of the controller (Figure 3-14) to a DEC 12-12314 (NEMA L21-30P; Hubbell 2811) plug. Input cord color
coding is: phase | - brown; phase 2 - black; phase 3 - black; neutral — blue; ground - green/yellow.
The input terminals are mounted on and connectdirectly to the 3-phasefilter, which provides low
impedance paths to groundfor high frequency components on the primary powerlines. Filter outputs
(3-phase wires and neutral) connect to the main circuit breaker, a 4-pole inrush-protected type fused at
30 A per pole and having two protective coils built in: a current coil that trips the circuit breaker to
OFFif the inrush current exceeds 30 A/pole steady state or 450 A for 1/2 cycle, and a trip coil that
provides automatic total shutdown of the system power whenair flow and/or overtemperature sensors
detect emergency conditions. Details of emergency shutdown implementation are covered in a later
subsection of this system description.
Three front-panel indicator lamps (Figure 3-14) turn on as soon as the powerplugis inserted into an
energized receptacle, regardless of breaker ON/OFFstatus.
As seen in the block diagram, the 3-phase output of the circuit breaker (CB1) providesfull 3-phase
powerto the following components of the controller:
Main contactor (K1)
3-phase stepdown transformer
Three duplex outlets (one per phase).
Oneleg of the 3-phase CB output is applied to a solid-state switch which, when closed by a command
received via the DEC powercontrol bus (parallel-wired three terminal connectors at the rear of the
controller), passes the 120 Vac to the coil of the magnetic contactor K1 to causeits closure. A paralleled MOV (metallic oxide varistor) and 0.1 wfd capacitor on each leg of the three phase output from
the contactor act to suppress the voltage spikes encountered when switching inductive loads (e.g., the
blower motors) connected to the output receptacles energized by contactorclosure. A total of 6 duplex
receptacles, two on each leg of the 3-phase supply, are energized by the power-up command. Each
duplex outlet receives its power through single pole, 20 A circuit breaker that permits manualdisconnect of any load at any time. These outlet breakers are not shown on the block diagram, and are
not used in the 869E controller.

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The 3-phase transformer (T1) provides a 3-phase output (3 windings) that-is rectified and filtered to
obtain a 25 Vdc output. This output is used to energize the trip coil of main circuit breaker CB1 upon
closure of the controller’s thermostat or receipt of an OFF (low) command from anyof the system
powersupplies. The latter commandoriginates with the closure of the overtemperature sensor located
on the heat sink for the output rectifiers of the +5 Vdc output of each supply. The total shutdown
command reaches the main CB via connector J9 (Figures 3-15 and 3-32). Total shutdown will also
occur uponreceipt of an unswitched shutdown command reachingthe controller via its connector J10.
The 25 Vdc output of the 3-phase transformer also feeds a 14 mA current source and a 15 V regulator.
The current source meets the specific requirements of the solid-state relay input circuit (a light-emitting
diode in series with a resistor). Light emission is cut off and the solid-state switch opens the 120 Vac
control signal to the main contactor (K1) when a LOW (ground)signalis received from either of the
air flow sensors whose associated blower (No. | or No. 2) is connected to switched phase 3 (Figure 312). This signal reaches the solid-state switch via controller connector J8 (switched shutdown). When
the contactor is deenergized, all power to devices connected to switched phasesis killed.
The 15 Vdc regulator outputis fed directly to the unswitched air flow sensor (AFS#2) located above
the memory powersupply (P.S. #3 in Figure 3-11). This outputis also fed to a 15 V switch consisting of
two transistors. After a power-up command hasenergized the system, this switch passes the +15 Vdc
to the two air flow sensors located above blowers | and 3, which operate off switched phase 3 (Figure

3-12).

Each air flow sensor (a pencil-shaped device approximately 4 inches long) is bracket-mounted in a
fore-and-aft position in the narrow space between the tops of the power supplies and the bottoms of
the card cages. Each sensor (Figure 3-33) consists of a barium-titanate sensing element, a control
circuit, and an SCR.
If the air flow sensor for unswitched power responds to a combined temperature/air velocity condition
exceeding design limits, its control circuit triggers the SCR to generate a ground return signal that
energizes the circuit breaker’s trip coil via a line to pin 2 of controller connector J10.
If either switched-powerair flow sensoris similarly energized, the returned ground signal deenergizes
the solid-state switch, which in turn opens the contactor to remove powerto all devices on the two
switched phases (2 and 3).
AIR PORT
+15 Vdc FROM
CONTROLLER
OUTPUT TO
CONTROLLER

CONTROL CIRCUIT

SCR

+ GROUND
[eaRIUM-TITANATE SENSING ELEMENT

Figure 3-33

Simplified Diagram of Air Flow Sensor

3-43

TK-0440

The purpose of the 15 V sense circuit is to detect the loss of +15 Vdc when the controller receives a
total shutdownsignal via connector J9. Upon detection, this circuit initiates a power request signal on
the powercontrol bus after a 1/2 second delay so that other cabinets can continue operation despite
main cabinet shutdown. A normally closed relay in the +15 V sense circuit effects this operation.
Figure 3-34 is a schematic of the 869D 3-phase powercontroller.
869E Controller (3-Phase, 240/416 V)
The 869E controller differs from the 869D controller in only two major points:
1.
2.

Input voltage
The elimination of the individual circuit breakers for each duplex outlet.

As seen from Table 2-2, 869E input voltage is 240/416 rather than 120/208. 869E input current capability and breaker size are correspondingly reduced (12 A/phase rather than 24 A/phase, and 15
A/pole rather than 30 A/pole, respectively).

The front panel drawings (Figures 3-14 and 3-16) show the physical similarity of the two controllers
(with the exception of the individual circuit breakers referred to above). The corresponding rear views
(Figures 3-15 and 3-17) are identical; i.e., the connectors (J4 through J10) are the same and in the same
locations. The duplex outlets are identically located and arranged in the same switched/unswitched
combinations.

The pilot control board 1s identical in both controllers. The input transformerfor this board is a 240 V

3-phase input type delivering the same voltages to the boardasits 120 V equivalent in the 869D. The
power contactor is also a 240 V version, as is the solid-state switch.
At the duplex outlets, the 869E is rated at 12 A per outlet as compared with 16 A peroutlet for the
869D. Output voltage is 240 Vac rather than 120 Vac.
As seen from Table 2-2, the two controllers have the same mechanical and environmental character-

istics, including rack mounting dimension 48.26 cm (19 in).

With one exception, the schematic of the 869D controller is the same as that for the 869E;1.e., the E
model does not have the individual outlet CBs that are provided in the D model. Accordingly, the

869E schematic is not included in this manual, even though provided in the printset.

869 Single-Phase Controllers (869C, 120 V; 869B, 240 V)
The technical description of the 869 3-phase controllers is also applicable to the 869 single-phase
controllers and is therefore not repeated here. However, phase and voltage differences entail some
componentvariations; these are summarized in Table 3-4.
With these differences and two others mentioned below, the block diagram of Figure 3-32 and the
schematic of Figure 3-34 apply to the 869C and 869B devices.
All four controllers in the present 869 family have the following basic similarities.
1.
2.

Use of the same (5413016) pilot control board
Provision for the same control signal inputs.

With respect to item 2, it should be noted that the Mate-N-Lok connectors for the single-phase 869s
have different J-numbers from the corresponding connectors of the 3-phase controllers; note also that
there are only two power control bus connectors (J10 and J11) in the single phase controllers as
compared with the three (J4, J5, and J6) provided in the 3-phase controllers.

3-44

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3-47

Figures 3-23 and 3-24 show front and rear views of the 869C; Figures 3-25 and 3-26 showfront and
rear views of the 869B. With the exception of nameplate differences, the front views of both single
phase 869sare identical; the rear views of the two controllers are identical with the exception of duplex
receptacle polarization (the neutral and the “hot leg’’ terminals are horizontally oriented for 240 V
output receptacles and vertically polarized for 120 V receptacles).
For 869C and 869B controller specifications, refer to Table 2-5.

3.2.4.2

866 Controllers - The 866D and 866E 3-phase controllers will be used in the VAX-11/780

main cabinets and SBI (system expansion) cabinets in systems delivered prior to June 1978. The 866D

is a 90-132 Vac, 47-63 Hz, 3-phase powercontroller. The 866E is its 180-264 Vac, 47-63 Hz equiva-

lent. The pilot control boards for the two controller types are identical and are discussed in the following subsection on the 866D only. Figure 3-9 is a simplified block diagram applicable to both units.
866D Controller (3-Phase, 120/208 V)

Figure 3-35 is a schematic of the 866D. For front and rear panel controls, indicators, outlets, etc., refer

to Figures 3-18 and 3-19. For specifications details, refer to Table 2-4.

As shownin the simplified block diagram, the 866D and 866E are conceptually similar to the 869.
However, the 866 does not have a magnetic circuit breaker that can be tripped for a total shutdown.
However, the control of the switched outlets via the DEC powercontrol bus and contactor is the same.

With the main circuit breaker manually set to ON, poweris always available at the unswitched outlets
until the breaker is manually set to OFF. The three indicator lamps (one for each phase) light whenever the plug of the input powercord is inserted in a live receptacle.
Poweris applied to the terminal block (mounted on the powerlinefilter) via a 4.5 m (15 ft) line cord or,
alternatively, can be hardwired to this block. The 3-phasefilter provides low impedance pathsto
ground forhigh frequency line components. If 120 Vac is present between phase | and neutral, lamp [1
lights. Similarly, if 120 Vac is present between phase 2 and neutral, [2 lights. [3 indicates ON status of
phase 3 when 120 Vacis present between phase 3 and neutral.
All 3-phase lines are connected to 30 A elements in circuit breaker CB1. All loads connected to the
power controller (both switched and unswitched) are controlled by 20 A circuit breakers (CB2, 3, and
4) for each outlet.
The coil associated with contactor K1 is energized by 120 Vac if a relay (K1) on the pilot control board
is closed. If the current through any outlet exceeds 20 A, the respective circuit breaker trips, removing

power from the loads.

Whencontactor K1 is closed, 120 Vac is applied across the switched outlets. The 0.1 wF capacitors (Cl
and C2) and the three MOVs(R2, R3, and R4) connected across the lines at the contactor reduce the
amplitude when switching inductive loads, thereby preventing interference with nearby electronic data
processing equipment.
The pilot control board contains the circuitry which allows remote turn-on and emergencyturn-off of
the switched power outlets in both 866 power control versions. These functions are accomplished by
controlling the voltage applied to the coil of relay K1 in the 866 powercontroller.
Basically the circuit consists of a triac operated by reed relay K1. Controlling this relay is a transistor
network which is’in turn controlled by inputs from connectors J2, J3, J4, JS, and J7. J2, J3, and J4 are
3-pin connectors which carry signals from the DEC power control bus. Pin | is the enable (power
request) line from the power control bus. Pin 2 is the disable (emergency shutdown) line from the
signal bus. Pin 3 is the common line. J7 is a 3-pin connector which carries signals from the LO-

CAL/OFF/REMOTEswitch on the front panel of the 866. Two additional lines (from the thermal

switch) are connected to pins | and 2 of JS.

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If the LOCAL/OFF/REMOTE switchis in the REMOTE position and pins 3 and | (on-J2, J3, or J4)

are connected throughthe transistor network, reed relay K1 turns on. There is a short turn-on delay

caused by an RC network in the base circuit of Q4, the transistor driving K 1. K1 in turn fires the triac,

SCR D21. This causes an energizing potential to be applied, through connector J6, across the coil
associated with contactor K1 in the power controller, thereby energizing the switched outlets. When

pins 2 and 3 of J2, J3, or J4 are connected (emergency shutdown is true) K1 is turned off, turning off

SCR D21. The resultant current through the coil is less than that required for holding the main relay
closed. Therefore, energizing potential is not present at contactor K1 and power is removed from
switched outlets.
Closing T (the thermal switch connecting pins | and 2 of JS) performs the same function as emergency
shutdown(1.e., connects pins 2 and 3 together). This switch is exposed to the ambientair surrounding
the power controller. Temperatures above 71° C (160° F) close the switch disabling the switched
outlets. The switch resets automatically when the temperature drops below 49° C (120° F).

Placing the LOCAL/OFF/REMOTEswitch in the LOCAL position provides a connection to ener-

gize relay K1 regardless of the state of the power request line on the signal bus. This switch position is
normally used for maintenance purposes; operations on the pilot control board are exactly the same
for situations where a connection is provided between pins 3 and | of the signal bus connector due to
closing of a circuit in an external device. A connection between pins 2 and 3 disables the switched
outlets, regardless of the position of the LOCAL/OFF/REMOTE switch.
866E Controller (3-Phase, 240/416 V)
Figure 3-36 is the schematic of the 866E. The operation of this controller as well as the number of
switched and unswitched outlets are identical to those of the 866D. Input voltage for this controller is
240/416, 3-phase, wye connected. The operation of the pilot control board was described in the preceding section on the 866D andis not repeated here.
3.2.4.3 861 Controllers - The model, frequency, and phase options for the single-phase 861B and
861C versions of this controller were listed in Table 3-1. Used in the Unibus Expansion Cabinet, this
controller is covered in detail in the 86/-A, B, C, D, E, F Power Controller Maintenance Manual (EK-

861 AB-MM-002). This manual is included in the VAX-11/780 documentation packages.

3.3

DC POWER DISTRIBUTION AND GENERATION

Figure 3-37 is a simplified diagram of the dc powerdistribution: in the VAX-11/780 system. All dc
poweris generated by the five H7100 power supplies previously referred to and discussed in more
detail in later sections of this manual.
3.3.1. Power Distribution
As seen in Figure 3-37, the basic system is serviced by three of the five power supplies; 1.e., those
designated as No. 2, No. 3 and No. 4 in the figure. Power supply No. 2 provides the 4 modules of the

DW780 Unibus Adapter (UBA) and some of the modules of the KA780/KU780 CPU with +5.1 Vdc

at 30 A; it provides -5.2 V at 10 A for the entire modular load shownin the figure by means of the basic
H7100 and its H7101 regulator. Power supply No. 3 provides +5.1 Vdc at 70 A to some of the modules
comprising the CPU and its writable control store (WCS), 1.e., the KA780/KU780, using the basic
H7100 alone.
Power supply no. 4 provides the five modules of the MS780A memory with +5.1 V at 50 A, +12 V at
10 A, +5 V at 20 A, and -5 V at 0.2 A. The +5 Vdc required by the time-of-day clock is provided by
the H7111 battery power supply (Paragraph 3.4.2.2). The H7112 is an optional battery backup supply
for P.S. No. 4, the memory supply.
Power supply No. | provides the 5 modules of the optional FPA with +5.1 V at 40 A, and power
supply No. 5 provides the two RH780 MBAs with +5 V at 20 A each.

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3-52

The basic dc power supply for the VAX-11/780 is the H7100, which delivers +5 Vdc at 100 A. Plug-in
switching regulators permit this supply to be configuredfor specific additional dc loads (Paragraph 3.3
DC PowerDistribution and Generation). The total load on any one supply never exceeds 500 W;;i.e., if
a supply delivers voltages other than +5 Vdc, the +5 Vdc amperageavailable is reduced by these other
demands. Five status indicators on the front of each supply provide general indications as to the
location of any malfunctions; a sixth indicator is lit whenever power supply operation is normal (Paragraph 3.4.3).
The H7100 power supply:
1.

Delivers the regulated dc output voltages required for central processor operation.

3.3.2

Senses several power supply malfunctions and provides visual (front panel) indications of

same.

Provides an overtemperaturesense signal to the powercontroller.

Incorporates current limiting and overvoltage protection.

Generates AC LO and DC LOsignals for use by the CPU in power-fail sequencing.

In conjunction with the H7112 battery backup power supply (an option), provides memory
refresh voltages during power outages of limited duration.

Power Generation - H7100 DC Power Supply

3.3.2.1 General - The VAX-11/780 power supply is the H7100, a 500 W unit that can supply several
dc output voltages in addition to its basic +5 Vdc, 100 A output. In concept, the supply is an ac-to-de
converter incorporating switching regulation of the dc outputs. The supply offers a choice of three
plug-in regulators. Either of two ac input adapters can be used, thus permitting operation from 120 or
240 Vac at 50 or 60 Hz line frequency. Also incorporatedin each adapterare protection circuits for the
powersupply and its loads, and a status display. The VAX 11/780 main cabinet provides space for up
to six H7100 supplies. The supply weighs 15.9 kg (35 lb) and is 178 mm (7 in) wide, 279 mm (11 in)
high, and 406 mm (16 in) in depth.

The basic concept employed in a switching regulator (Figure 3-38) is to vary the duty cycle of the
pulsed dc applied to a power transformer whoserectified and filtered output providesa relatively lowvoltage, high-current source for the computer’s logic and control circuits. The single-line diagram of
Figure 3-39 showsthe functional elements of the H7100. The +300 Vdc output of the raw dc section 1s
applied to a 20 kHz dc-to-ac inverter whose duty cycle is varied as a function of sensed output voltage
variations relative to an accurate +5.1 Vdc reference signal. The inverter provides isolation between
the line and the load. The variable duty cycle ac is stepped down through a transformer, rectified and
filtered. Duty cycle is controlled by a pulsed transistor switch and a base-driver transformer whose
primary winding is energized by the output of a 20 kHz pulse-width modulator.

3-53

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With one exception (the —5 B output of the H7103 at 0.2 A, as shown in Figure 4-12) the regulation of
all dc output voltages is accomplished in the same way as the main +5 Vdc output. Figure 3-40
illustrates the basic regulator concept, including provision for overcurrent sensing and limiting, and
crowbar load protection from overvoltage generated by the supply. Table 3-5 compares the design
features in the H7100 regulator options. The floating +30 Vdc inputs to the switching buck regulators
correspond to the +150 Vdc inputs to the main switching regulator (Figure 3-39). Op amp output
(Figure 3-40) serves as the input (error voltage) signal to the ramp generator in which a capacitor is
charged to a constant limit voltage equal to the reference. Rate of charge is proportional to error
voltage and determines the projection of the maximum voltage point on the horizontal (duty cycle)
axis of the ramp slope waveform. This relationship causes pulse width to vary as a function of error
voltage, and is referred to as pulse width modulation (PWM). PWM frequencyis determined by the 20
kHz clock. PWM output controls the duty cycle of the switching regulator (and hence the output
voltage) in closed loop operation.
Figure 3-41 is a sketch identifying the +5 Vdc output and return terminals, power-fail connector J3,
overtemperature connectors J4 and J5, and a cutout for installing connector J6 (H7101 regulator
output) or J7 (output from H7102 and H7013 regulators).
Figure 3-42 identifies the decals affixed to individual H7100 power supplies to show their regulator
complement. Table 3-6 lists the pin identifications for H7100 output connectors J6 and J7.

REGULATOR

TRANSISTOR

30 VDC

SWITCHES

CURRENT

SENSOR

STEPDOWN

(SHUNT)

XFMR

RECTIFIER

& FILTER

OUTPUT

V SENSE
REGULATOR

cROWBAR

PRE-DRIVE

0.V.

i
PULSE

ERROR

RAMP

WIDTH
MODULATOR

OP AMP

GENERATOR

REFERENCE
VOLTAGE

KN
20
CLOCK

TK-0468

Figure 3-40

Block Diagram of Typical H7100 DC Power Supply Regulator

3-56

Table 3-5

Comparison of Regulator Features in H7100 Power Supplies

H7101
(-5 V)

H7102
(+12 V)

H7103
(+5 V)

Base Drive Circuit

Power Switch

XxX

Error Amplifier

»4

X (+5 B only?)

Ramp Generator

XxX

Clock

xX
(+5 B and -5 B)

Pulse Width Modulator

Reference Voltage Source

Overcurrent Circuit

X (+5 B)

Overvoltage Circuit

X (+5 B)

CrowbarCircuit

p,4

X (+5 only)

DC Voltage O.K.

Output Circuit

»4

Status & Sequence Circuit*

Xx
X
(on H7103){ (-5 B) and for

+12 V

Turn-off Drive Circuit

Flyback Diode

Slow Run-Up Circuitt

Negative Regulator

—-5 B Regulator

XxX

*S&S circuit is required if the voltage goes to memorychips.
+Slow run-up provides controlled build-up of reference voltage to prevent overshoot when supply
voltage is coming up from zero or from a crowbarshort.

3-57

CUTOUT FOR INSTALLING

OUTPUT JACKS J6 OR J7

OO®
OGIO:
@

<<?

OOOWVd0O

O0000

POO! [Om
acto

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—__|

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(SEE FIG. 3-32)

J3
POWER
FAIL (TO CPU)

AC LO

BLK

REGULATOR
DECAL

Fomen|@plonsarewr
@lsyanrew"
BUS

RED

OVER TEMPERATURE

RETURN

CONTROL @ SIGNAL
.

BUS

(3) OVERTEMP.
TK-0437

Figure 3-41

H7100 Power Supply — Rear Panel Connectors

3-58

H7100
Power Supply
15 —PIN CONNECTOR
a—_.
_—_—

NOT USED IN
THIS OPTION

+5V @ 100 AMPS
OUTPUT BUS

H7100
H7102 & H7103

H7100
POWER SUPPLY

J7 15 PIN CONN

REGULATOR BOARD
,

POWER SUPPLY WITH
BATTERY BACKUP &
REGULATOR BOARD
“

WITH H7101

+5B @ 20A, —5B @.1A
+12 @10A

J6 15 PIN CONN

—5V @ 30 AMPS

OUTPUT BUS
+5V @ 50 AMPS

OUTPUT BUS
+5V @ 75 AMPS

DECAL 3614762-01

DECAL 3614762-00
TK-0433

Figure 3-42

Decals Showing Regulator Complement of H7100 Power Supplies

3-59

Table 3-6

H7100 Power Supply Output Connectors J6 and J7 — Pin Identifications
J6

Pin No.
|
2
3
4
5
6
7
8
9
10
1]
12
13
14
15

Pin Identification

Pin No.

-5V
-5V
-5V
-5V
-5V
-5V
NC
NC
NC
RTN
RTN
RTN
RTN
RTN
RTN

|
2
3
4
5
6
7
8
9
10
11
12
13
14
15

Pin Identification
+12 VB
+12 VB
RTN
RTN
+5 VB
+5 VB
+5 VB
+5 VB
RTN
RTN
RTN
RTN
RTN
-5 VB
-5 VB

NOTE
All return (RTN) leads are tied together.
Tables 3-7, 3-8, and 3-9 summarize the characteristics of the two power supply options (H7100A and
H7100B), the regulator options, and the battery backup power supply options, respectively.
The plug-in regulator optionsare:
Model H7101 —- delivers -5.2 Vdc at 30 A
Model H7102 - delivers +12 Vdc at 1O A
Model H7103 —- delivers +5 Vdc at 20 A and —-5 Vdc at 0.2 A.

The battery backup supplies designed for use with the VAX-11/780 are:
Model H7111 - delivers +5 Vdc at 0.012 A to the time-of-day clock during normal power-up
operation and for a minimum power-fail period of 100 hr.
The H7111 also generates BAT DC LO.
Model H7112 - Under power-fail conditions, delivers +36 Vdc to the H7102 and H7103 regulators at a discharge rate of 250 W for 10 minutes to refresh the MOS memory. Has terminals for
an external battery that can be added to extend operating time.

"PWN

The H7100 dc power supply (Figure 3-43) has the following major assemblies:
Front panel (AC input adapter)
Middle panel
Rear panel
Major (mother) board
Control board.

3-60

Table 3-7

VAX-11/780 DC Power Supply Options

Model No.

Voltage

Input
Freq. (Hz)

Voltage

Output
Amperes

Watts

H7100A

120

50-60

2 P-20A

+5.1

100

500

H7100B

240

50-60

2 P-20A

+5.1

100

500

Table 3-8

H7100 Power Supply Regulator Options

DC Output
Designation

Volts

Amperes

Watts

H7100
H7100 with H7101 Regulator
P/N 7014956-00 for 120 V supply
P/N 7014956-01 for 240 V supply

+5
+5
-5

100
75
30

500
375
150

+5
+12
+5B
-5B

50
10
20
0.2

250
120
100
l

H7100 with H7012 and H7103 Regulators
P/N 7014957-00 for 120 V supply
P/N 7014957-01 for 240 V supply
H7100
H7102
H7103

Table 3-9 VAX-11/780 Battery Power Supplies
Output

Backup
Operating Time

+5 Vat12mA

100 hr

+36V(to+l2and

10 minat 250 W

Designation

Backup For

H7111A

Time-of-day Clock
Battery Supply

BAT DC LO

H7112A

MemoryBattery

H7111B

H7112B
H7112C
H7112D

Backup Power
Supply (optional)

+5 regulators)

3-61

Input Voltage
and Frequency

120 V /50-60 Hz

240 V /50-60 Hz

120 V /60 Hz

240 V/50 Hz
120 V/50 Hz
240 V /60 Hz

CONTROL BOARD

REAR PANEL

MAJOR BOARD

MIDDLE PANEL

FRONT PANEL
(AC INPUT ADAPTER)
TK-0449

Figure 3-43

H7100 DC Power Supply — Top View

3-62

The larger components on each of these assemblies are identified in Figures 3-44 through 3-47.
Table 3-10 lists the pin identifications for the battery adapter connector (9-pin J2) at the bottom right
of the H7100 front panel (Figure 3-44).

(©) POWER NORMAL
(©) PLUG IN REGULATOR FAILURE

H7100A
120V
12A
50/60@ Hz

OFF

O POWER INVERTER FAILURE

(| OVER TEMP

SEE TABLE
\Y~ 3-9

BATTERY
ADAPTOR
TK-0441

Figure 3-44

H7100 DC Power Supply Front Panel AC Input Adapter (Front View)

3-63

AC INTERCONNECTOR
P1/ J8

MIDDLE PANEL
RIBBON
CABLE

TO STATUS
BOARD
CONNECTOR
GY ,
31/32
i

-@Q

—
QC

7
—_—— eee oe

ot x —

STATUS BOARD

2P AC
CIRCUIT
BREAKER
CB1 20A
LINE FILTER

AC INPUT
CONNECTOR
J1

BATTERY
ADAPTER
J2

TK-0447

Figure 3-45

H7100 DC Power Supply Front Panel AC Input Adapter (Rear View)

3-64

FILTER
CHOKES
L1 & L2
FOR +30V
& F30 V
OUTPUTS

REAR OF
MIDDLE PANEL
MAIN LINE
FUSE 1/8A
SLO-BLOW

382, BW
IN-RUSH LIMITING
RESISTOR

J7 (10 TERM.)
BOARD

FLOATING
30V OUTPUT
CAP

REAR
PANEL

11/2 A FUSE
FOR
BIAS/ CONTROL
BOARD

35 wh
+5.1 Vdc
OUTPUT
CHOKE
o

Chae

pu th

T4 BALUN
FOR Q1/Q2

R7-R10
FUSIBLE
RESISTORS
SWITCH |

SENSE

O.T.
SENSOR

MAIN PULSE
TRANSFORMER
T2
SHUNT

FOR

100A 0.C.SENSE

TRANSFORMER
T3

+5 Vdc
OUTPUT CAPS C3 & C4
(15,000 MFD EA.)

HEAT SINK

FOR SCHOTTKY

+5 Vde & 30V(2)

DIODES,
SNUBBER

OUTPUT XFMR

NETWORK,
& CAPS.
FOR +5.1V
OUTPUT
TK-0504

Figure 3-46 H7100 DC Power Supply - Component Identification
(Front and Rear Panels Detached from Chassis)

3-65

+30 Vdc
OUTPUT CAP

J6 TERMINAL
BOARD (BELOW P1/J8)
P1A/J8 MAIN
POWER
INTERCONNECTOR

FLOATING
30 Vde
OUTPUT
CAP
START-UP &
AC SENSE
XFMR
T1

IN-RUSH
RESISTOR
CUTOUT
RELAY K1

REAR PANEL
J1FORH7101 OR
H7103 (24 PIN)

POWER BRIDGE
RECTIFIERS

J2 for H7102
(24 PIN)

POWER SWITCH
TRANSISTORS

HEAT SINK

FRONT PANEL

POWER SWITCH
TRANSISTORS

FILTER CAPS
FOR
BIAS/CONTROL
POWER
|

BIAS/CONTROL
BOARD

T5 BALUN
FOR Q4/Q3
TK-0446

Figure 3-47 H7100 DC Power Supply - Component Identification
(Front and Rear Panels Attached to Chassis)

3-66

Table 3-10

H7100 DC Power Supply Battery Adapter (Connector) J2 — Pin Identification
Pin No.
l
2
3
4
5
6
7
8
9

Pin Identification
+36 V Battery
+36 V Battery
Relay Closure, CB1-C
AC LO
NC
Relay Closure, CB1-N.O.
+36 V Battery Return
+36 V Battery Return
NC

NAARWN

3.3.2.2 Block Diagram Description - The block diagram of Figure 3-39 shows the major functional
areas described in the following subsections.
AC input
Raw dc
Transistor switch and base-driver transformer
30 V section

Bias power supply for control circuits of H7100
Control section
Protection circuits.

AC Input
The ac adapter (front panel) (Figure 3-45) is a rectangular box that is fastened to the middle panel
(Figure 3-43) by two Phillips screws. There is one adapter for 120 Vac input and another for 240 Vac
input. Both adapters consist of an ac connector,line filter, 2-pole circuit breaker, power supply status
board, and the plug portion of the ac interconnection plug/jack combination.
A 3 ohmresistor and a relay (K1) are mounted on the middle panel (Figures 3-46 and 3-47). K1 shorts
out the resistor as soon as the input capacitors of the raw dc section are charged at power turn-on.
Raw DC
Whenthe supply is used on a 240 V input, the rectifiers are connected as a fullwave bridge and,
combined withthefilters of this section, produce an output of approximately 300 Vdc. When operated
on a 120 V input, this circuit functions as a voltage doubler delivering 300 Vdc at nominalline voltage.
The voltage doubler is essentially two halfwaverectifiers of opposite polarity stacked in series.
rransistor Switch and Base-Drive Transformer
The 300 V raw dc is applied to a dc-to-ac inverter that chops the 300 V raw dc at a 20 kHzrate. The
three outputs of the transformer are rectified and filtered to produce two unregulated 30 Vdc sources,
and +5 Vdc output circuit whose regulation 1s effected by varying the conduction pulse width(i.e., the
duty cycle). The inverter consists of two transistor switches, the power transformer, reset diodes, and
snubbercircuits. Each transistor switch is actually two transistors connected in parallel. Base drive to
the transistors is provided by a single transformer with four secondary windings(onefor eachtransistor) and two primary windings. One of the two primary windingsis in the emitter circuit of the dc
powerstage and provides base drive proportional to emitter current. The other primaryis tied to the
inverter control circuits to provide for inverter turn-off and turn-on.

3-67

The duration of a complete cycle is 50 ws. A cycle comprises three segments: conduction, transformer
reset, and dead time. During conduction, all transistor switches (Q1 through Q4) are on, connecting
the dc source to the transformer primary. In the secondary, power conducted through the halfwave
rectifier diodes charges the filter chokes. The voltage across the primary is the raw dc voltage (300
Vdc), while the voltage across any secondary winding is proportional to the stepdown turns ratio.
When conduction stops, the transformer magnetizing current (which builds up during the conduction
portion of the cycle) continues to flow. The transformer primary voltage reverses, increasing until it
reaches the level of the raw dc input, at which point the reset diodes conduct. This reset condition

continues until its time equals the conduction time. During reset, the inductive energy stored in the
core of the transformer is returned to the raw-dc capacitor bank. Reset is completed whenthe transformer primary current is reduced to zero. At this time, the circuit is at rest and no poweris conducted.
Dead time is maximum at high line and minimum atlowline.
30 V Section
The 30 V section provides two unregulated dc outputs for the two optional plug-in regulators. The
outputs of the two 30 V sections are derived in the same wayas the 5 V outputjust described. The 30 V
output is used for the +12 V H7102 regulator; the F30 V outputis for the -5 V H7101 regulator. The
H7103 +5 V regulator uses both 30 V outputs and regulated +12 Vdc from the H7102 board.
Bias Supply for Control Circuits of H7100
The bias supply provides +12, -12 and +5 Vdc bias voltages for the control circuits of the H7100 and
all plug-in regulator options. This supply is a flyback (single-ended switch, off-line converter) type that
operates from the same raw-dc source as the main converter.
Inductive energy is built up in the primary of the transformer when the power switch(a single transistor) is on. Secondary conduction is blocked during this time by the secondary dioderectifiers. When
the switch turns off, power is conducted to the load from the transformer,the inductive source. Regulation is achieved by controlling the conduction pulse width of the powerswitch that regulates the +12
V. The -12 V is unregulated, but closely tracks the +12 V. The +5 V bias voltage is obtained from a 3terminal regulator operating from the +12 V source.
The start-up and ac sense transformer on the motherboard provides +12 Vac for the start-up supply/ac monitor on the bias control board. The supply/monitor circuit provides the +11 Vdc required
for power supply control during the interval required for the bias supply to come upto full power.
Control Section
The control section (Figure 3-48) consists of a regulator control circuit, a clock, and a pulse amplifier.
The regulator control circuit consists of the +5.1 V reference, the comparison operational amplifier,
and compensation circuits, all of which control the +5 V regulation. The feed-forward circuit monitors
the peak pulse voltage on the transformer secondary, which is always proportional to the raw dc
voltage. This signal is used to bias the ramp generator suchthat the control circuit responds to changes
in line voltage. The control and feed-forward signals are summedinto the ramp generator to produce a
delay in the PWM proportional to the sum of the two signals. This delay determines the conduction
pulse width.
Protection Circuits
The output of the PWM canbe shortenedor interrupted by any of several circuits used to protect the
power supply. Overcurrent becomesactive when the +5 V output current exceeds 120 A. Thiscircuit is
a pulsing foldback type that limits the short circuit current to approximately 40 A, rms. Current pulses
occur at approximately 60 ms intervals after the 120 A maximum limit 1s reached. The current limit
circuit resets the slow run-up circuit, which then tries to restart the supply. The peak primary current
limiter terminates a pulse when the switch (primary)current exceeds approximately 16 A. The crowbar
sense stops all pulsing briefly when the crowbarfires.

3-68

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3-69

3.4

POWER-FAILURE PROVISIONS

WkwnNe

The following power-failure provisions are incorporated in the VAX-11/780.
Power-fail sequencing circuitry
Battery backup powersupplies (one for the TODC, and an optional one for the memory)
Power-failure indicators in, and AC and DC LOsignals from, the H7100 power supplies
Power controller overtemperature sensor
Cabinet air flow sensors.

3.4.1 Power Sequencing Circuit
The CPU power-fail sequencercircuit ensures that the CPU, and the 11/03 microcomputer (whichacts
as a CPU console) correctly respond to all power-up/power-down sequences that can be reasonably
expected to occur in a system. Cases resulting from device or componentfailure are not considered.
The sequencer generates the power-fail interrupt for the CPU and theinitialization signals that clear
registers and flip-flops, and force microcode into power-up routines.
3.4.1.1 Requirements —- The power-fail sequencer must satisfy constraints imposed by the SBI (Synchronous Backplane Interconnect) protocol, the Q-bus protocol, the CPU implementation, and the
power system implementation. The following discussion covers the major aspects of the power sequencingcircuitry.
3.4.1.2 SBI Power-Fail Constraints - Figure 3-49 is a timing diagram for the power-down/power-up
sequences. The following constraints are indicated.
1.

The minimum assertion time for either the FAIL (AC LO) or DEAD signals is 5 us.

FAIL maybe asserted without DEAD being asserted, but DEAD must always be preceded
by the assertion of FAIL.

The requirement for an assertion time of not less than 5 ms between FAIL (AC LO) and
DEAD (DC LO)allows program time for the CPU to save state in the memoryand to halt.

The greater than 2 us time between DEAD assertion and CLK indeterminancy allows devices such as memories to complete the cycle in progress at the assertion of DEAD.

The greater than 5 us time between DEAD assertion and loss of DC PWR allows devices
such as the disk controllers to stop disk activity before loss of power.

The greater than 25 us time between the regaining of DC PWR andthe deassertion of
DEAD allows time for the clock to warm up. This interval is the minimum that the power
supply must guarantee. The system will artificially assert FAIL and DEAD foran additional
100 ms that is required bythe oscillator used.

The greater than 2 us interval of stable clock before the deassertion of DEAD allowssynchronousinitialization in devices.

The greater than 5 us time between DEAD deassertion and FAIL deassertion allowsall
initialization signals to be removed before devices attempt to set the POWER UP interrupt.

Minimum deassertion times for FAIL and DEAD arenotspecified.

3-70

(

DC POWER

|
>2 us—|

-—?—.

|.
kK-— >2 uS

(

TC
)

]

po,

CLOCK

——

DEAD L

—+

>5uS

kK-

> 25 us

|_|

POWER DOWN
SEQUENCE

POWER UP
SEQUENCE
TK-0428

Figure 3-49

POWER DOWN/POWERUPTiming Diagram for SBI Power-Fail Conditions

3.4.1.3 Q-Bus Power-Fail Constraints - Figure 3-50 is the timing diagram for the Q-bus powerup/power-down sequence. The following constraints are indicated.
|.

The assertion of BPOK (Q-BUS AC LO) requires 8 ms of de powerreserve and the previous
assertion of BDCOK (Q-BUS DC LO)forat least 70 ms. With these requirementssatisfied,
BPOK must then beasserted for at least 3 ms.

BPOK deassertion requires a dc powerreserve of 4 ms and the deassertion of BPOK for not
less than 1 us.

BDCOK (DC LO)assertion requires that dc power was good for the preceding 3 ms and the
assertion of BDCOK forat least 1 us.

BDCOK deassertion must occur 5 us before the loss of DC power, but at least 4 ms after the
deassertion of BPOK (AC LO). BDCOK mustbe deasserted for at least | us.

Because of the several (up to 5) independent power supplies used in VAX-11/780 systems, the minimum assertion times established for BPOK (AC LO) and BDCOK (DC LO) cannot be guaranteed. If

minimum assertion times for these parameters are not achieved, the effects on the 11/03 micro-

processor and other Q-bus devices can besignificant. For example, if BPOK is deasserted during a
power-up routine and is not followed by a BDCOK deassertion, the microprocessor is left in a hung
condition. For this reason, the power-up and power-down routines must be so designed that the
system is insensitive to the invocation of a power-down routine before the power-up routine is completed.
Since the console system (including the 11/03 microprocessor) does not preserve any processor state
for the duration of a transient powerfailure, the system is insensitive to the incompletion of a powerup routine if BDCOK is deasserted in order to clear the possible hung condition, and force the microcode routine back to the beginning of the power-uproutine.

3-7]

—
BPOK H

3MsMiIN

(

—|

f-—

70MSMIN

—

4MSMIN

|
k—

(

BDCOK H

—
DC POWER __

le-—3 MS MIN

8 MS MIN

—el

5MSMIN

+-—
|

POWER DOWN
SEQUENCE

POWER UP
SEQUENCE

TK-0427

Figure 3-50

POWER UP/POWER DOWNTiming Diagram for Q-Bus Power-Fail Conditions

3.4.1.4 CPU Constraints - Inasmuch as the 11/03 microprocessor and its power supply are part of
the CPU system hardcore, both must be functioning before the CPU can operate. From a system
viewpoint, both CPUs and their power supplies must interact in the following manner.
1.

Anyfailure or outage of a CPU powersupply or the 11/03 power supply should cause both
CPUs to fail; 1.e., the first power supply to assert AC LO will cause assertion of the system
AC LOsignal and deassertion of Q-BUS BPOK H (AC LO).
Neither CPU will recover and powerup until all power supplies are operating normally; i.e.,
the last supply to release DC LO and AC LO causesthe deassertion of system DC LO and
AC LO; it also deasserts Q-BUS BPOK H (AC LO) and BDCOK H (DC LO), thereby
powering up both CPUs.
Since the SBI interface is included in the hardcore, the assertion of CPU system AC LO and
DC LO must be caused bythe assertion of FAIL (AC LO) and DEAD (DC LO) on the SBI.
To avoid multiple interrupts in brownout conditions, and to ensure proper sequencing of the
CPU and the 11/03 microprocessor, the following protocol is enforced within the system.
a.

AC LOand DC LO and their equivalents in the SBI and Q-BUS (i.e., BPOK H, FAIL,
etc.) must remain asserted by the power supply or other driving device for a minimum
of 5 ws. It should be noted, however, that a similar constraint concerning minimum

deassertion time cannot be made because of the asynchronous nature of these signals.
For example, when AC LO goeshigh thereis the possibility that another supply will
immediately assert it, pulling it low again. The result is the possible deassertion of AC
LO and DC LOforarbitrarily short periods. However, a minimum 5 usassertion can
be guaranteedif all drives meet their specifications.
b.

The AC LO seen by the CPU and the 11/03 must, once asserted, remain asserted for at

At the end of the 5 ms AC LOassertion, DC LO (as seen by the CPU and the 11/03)
must be asserted for at least 1.0 ws in order to force microcode in both CPUs into
initialization routines.

least 5 ms in order to prevent multiple power-fail interrupts.

3-72

AC LO (as seen by the 11/03, and hence the rest of the system) must remain asserted

Under normal conditions, DC LO should not be asserted unless AC LO 1s asserted.

for a minimum of 70 ms after the negation of system DC LO. This constraint is imposed by the 11/03 and various Q-busperipherals, but will not hurt system performance because power up may not be completed without intervention by the 11/03
anyhow.

It should be noted that a CPU system powerfailure does not cause the assertion of FAIL and DEAD
on the SBI. The location of the SBI clock and terminator in the CPU backpanel is such that the SBI
protocol for these signals is correctly executed, being independent of CPU internal operation.
3.4.1.5 Power System Constraints —- The H7100 supplies (but not the 11 /03’s supply) conform to SBI
timing constraints, FAIL L being equivalent to AC LO H and DEAD L being equivalent to DC LO H.
As indicated, the minimumassertion time of the fail signals can be guaranteed, but minimum deassertion cannot be.

I AUWARONS

Barring catastrophic failure, each power supply will be so designed as to guarantee the following.
DC LO will never occur without AC LO.
AC LO can beasserted without DC LO.
The minimum assertion time of AC LO or DC LOis 5 us.
AC LO 1sasserted at least 5 ms before DC LO.
AC LO 1s asserted for a minimum of 5 ws after DC LO deassertion.
Poweris good for 5 us after DC LO assertion.
Poweris good for 25 us minimum before DC LO deassertion.

It will be recalled that the CPU receives its power from as manyasthree supplies; the 11/03 microprocessor has its own internal power supply.

3.4.1.6

Circuit Description - The circuits used to implement the CPU power-fail and initialize se-

quencing are located on the clock (CLK) module. The drivers and receivers for the Q-bus are located
on the console interface (CIB) module.

Fail-Safe Bus Drivers
To guarantee the integrity of the SBI and Q-bus power-fail signals (FAIL, DEAD, BPOK, BDCOK)
during transitions of the power supply output, special drivers are required for these signals. An Nchannel J-FET is used in a common-source configuration to drive the bus power-fail signals. The JFET is seen as a 10-ohm resistance to ground whenthe gate source voltage is approximately zero.
Whenthis potential is more negative than -7 V, the J-FET appears as an open circuit to ground and
the drain is pulled up to +3 V bythe bus terminator.
Each power supply in the CPU asserts AC LO H and DC LO byguaranteeing that the output
voltage at these terminals is zero. AC LO H and DC LO aredeasserted by applying -12 V to these
terminals.

The AC LO H and DC LO H outputsof the power supplies should not be wire-ORed, butthe contrary

is true for the drains of the J-FETs. Each supply can drive as many of the J-FETsas is necessary. A
circuit identical to the bus driver and in parallel with it is used to generate internal AC LO L and DC

LO L.

3-73

The CPU power-fail and initialize circuit uses a set of four J-FETs with wire-OReddrains to generate
each of the following signals:

FAIL L
DEADL
BPOK H
BDCOKH
PSACLOL
PSDCLOL

(SBI)
(SBI)
(Q-bus)
(Q-bus)
(CPU)
(CPU).

Other Bus Drivers and Receivers
Thesignals that drive the SBI and Q-bus power-fail signals artificially (to meet system constraints) will
always have good powerat the times they are relied upon and can therefore be standard, open-collector TTL gates. The bus power-fail signals must be received with a low-input current, high-threshold
bus receiver; 1.e., DEC 8640. The received bussignals used by the sequencercircuit are:
DEAD L
FAIL L
AC LO (Q-bus, buffered BPOK H).
The power-fail receivers are buffered from any edge-triggered circuits by a “‘glitch catcher’’ for the
power-fail deassertion edge of the signals. Thefiltering provided by the “glitch catcher’’ is necessary
because, in the “last one to let go releases the bus” implementation, transients will occur on the bus
when the current from a just-released driver redistributes amongthestill-asserted driver or drivers.
The length of the transients will be one round trip time on the busor less. The circuit used filters out
transients up to 100 ns (approximately), which is approximately two round trips on the SBI or the Qbus.
Inputs and Outputs
Figure 3-51 shows the inputs and outputs of the power-fail sequencer circuit. This circuit is edge
triggered from AC LO, butis self-restoring. Thus, without continuedassertion of a DC LO equivalent
the normalstate will be resumed. The console reset input forces SYSTEM INIT (U Program initialize)
without affecting the remainder of the sequencercircuit.
3.4.1.7 Sequencer Operation — The power-fail sequencercircuit is triggered from the assertion edge of
ORed AC LOequivalents; a signal called AC LO OR FAIL. This signal clocks the power-fail interrupt
flop and is used as a 1-bit BEN (branch enable) test by microcode. Assertion of power-fail interrupt
results in the starting of the power-fail timeout and the setting of the FORCE AC LOflop. At the end
of timeout, FAKE DC LOisset, which in turn sets the FORCE DC LO flop. FAKE DC LOis an
internally generated DC LO equivalent and is ORedin with the other DC LO equivalents. The ORing
of the DC LO equivalents sets the FORCE DC LOflop and causesthe assertion of the SYSTEM
INIT, and the UPROG (U-Program) INIT signals that initialize the CPU.
On the deassertion edge of the ORed DC LO equivalents, a 3 ms timeout to clear FORCE DC LO
starts. After FORCE DC LOis cleared, a 70 ms timeout to clear FORCE AC LOisstarted. Once
FORCE AC LO 1scleared, the circuit 1s ready to accept another power-fail signal.
A maintenancecircuit, activated by grounding a backpanel pin, causes the power-fail sequencercircuit
to cycle repeatedly through a series of power fails and returns.

3-74

FAIL (FROM SBI)
CPU ACLO

ACLO (FROM Q-BUS)

CPU DCLO

ACLO (FROM ORED POWER SUPPLIES)
DEAD (FROM SBI)

POWER-FAIL
SEQUENCER

DCLO (FROM ORED POWER
| SUPPLIES)

CLOCK OF
MODULE

_»

POWER FAIL INTERRUPT
ACLO (FAIL}

DCLO (FROM TODC BATTERY
BACK-UP POWER SUPPLY)

>
a

ACKNOWLEDGE POWER FAIL

SYST INIT

CONSOLE RESET

UPROG INIT

(FROM INTERRUPT ARBITRATION LOGIC)

TK-0430

Figure 3-51
3.4.1.8

Power-Fail Sequencer — Inputs and Outputs

Power Sequencing Terminology

FAIL Signal
The FAIL signal is asserted by NEXUS* (whose existence in the system is necessary for the proper
restart after a powerfailure, i.e., memory and CPU NEXUS. The purpose of FAIL is to provide a
restart signal to the CPU, so that a system restart operation may be initiated. CPUs are the only
NEXUS that recognize the FAIL signal.
Assertion of FAIL
A NEXUS asserts FAIL asynchronous to the SBI clock during the assertion of the power supply AC
LO at that NEXUS. The assertion of FAIL inhibits CPUs from activating a power-up routine. SBI bus
Operation may continue during the assertion of FAIL.
Deassertion of FAIL
FAIL is deasserted asynchronously when all NEXUS required for the power-up routine operation
have detected the deassertion of AC LO. CPUs sample the FAIL signal at an appropriate time after a
power-downroutine (assertion of FAIL) to determine if a power-up routine should be enabled.
DEAD Signal
The DEAD signal is asserted asynchronously to the SBI clock when an impending powerfailure to the
clock circuit or bus terminating network is detected. NEXUS attached to the bus usethis signal to
prevent invalid data from being received while the busis in an unstable state. NEXUS maynotassert
any SBI signal when DEAD is asserted. Dead is to be interpreted as a reset function equivalent to
NEXUS DC LO.
* Any device connected to the SBI (synchronous backplane interconnect).

3-75

Assertion of DEAD
The assertion of power supply DC LOtothe clockcircuit or terminating networks causesthe assertion
of DEAD. DEAD isasserted asynchronously to the SBI clock and occursat least 2 us before the clock
becomes inoperable. When the clock is inoperable due to powerloss, its behavior is unpredictable.
Deassertion of DEAD
DEAD is deasserted when DC LO is deasserted at the clock circuit or terminating networks. The clock
is operational for at least 2 us before the deassertion of DEAD.
3.4.2 Battery Backup Power Supplies
The basic VAX-11/780 system includes a battery backup power supply for the system time-of-day
clock, and an optional battery backup powersupply for refresh of the MOS memoryis also available.
Both supplies operate as uninterruptable power sources having dual-rate chargers andself-contained
batteries. When a powerline outage or voltage dip occurs, both supplies are automatically transferred
to a mode in whichthe batteries take over the functions of the associated dc power supplies.
3.4.2.1.

H7112 Memory Battery Backup Power Supply - The H7112 comprises:

A constant-current, dual-rate battery charger

Three 12 V, 5 A/hr, sealed lead-acid batteries (DEC P/N 12-12499-00).

When fully charged, the battery pack will supply up to 250 W into a constant power load for 10
minutes. The power required from the external battery is 280 W. Recharge time is 14 to 16 hr. For
other H7112 performance specifications, refer to Table 2-9.
Mechanical Configuration
The H7112 (Figures 3-52 and 3-53) is housed in a rack-mountable cabinet that is side and top ventilated by natural convection through louvers. The cabinet weighs approximately 11.25 kg (25 Ib) and
has the following dimensions:
Height - 13.2 cm (5.2 in)
Width —- 48.3 cm (19.0 in)
Depth - 15.6 cm (6.2 in)
Interchangeable input assemblies permit operation from either 120 or 240 Vac supplied by the power
controller of the cabinet containing the H7112 unit (refer to the ac powerdistribution diagrams of
Figures 3-10 and 3-11). Two auxiliary battery terminals (J12 and J13) enable connection of an external
battery supply if extended holduptime is desired. However, a charging circuit is not provided for this
external source. Since the internal and external batteries are diode-buffered only, their load-sharing

characteristics and relative discharge rates will depend upon theparticular situation.

Two 3-pin connectors (J10 and J11 at the rear of the unit) provide for H7112 interface with the DEC
powercontrol busin order to effect shutdown of the H7112 whenever the emergency shutdown command appearsin the bus.
The output connector J7 is mounted on the single PC board (5412675) in the H7112. Connections to
the 11/780 are via a cable entering theleft side of the unit (refer to detail A of Figure 3-52).

3-76

SEE DETAIL B

FUSE
1A/0.5A

LED FAST-CHARGE INDICATOR
(VISIBLE THROUGH COVER LOUVERS)

SEE DETAILA

SLO-BLOW

nense

13.2 CM.
(5.2 IN.)
SHIELD ASSY

SSUES
SSSSSSSSS
SSS) SS WSS

OFF/ON
SWITCH

Re~
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~
15.6 CM
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SSSSSS

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TK-0451

Figure 3-52.

H7112 Memory Battery Backup Power Supply — External View
3-77

15.6 CM.
(6.2 IN.)

COVER

CHASSIS

HEAT SINK

AUX

BATTERY
TERMINALS

CHARGE

CKT BD

BATTERIES

(3-12V IN SERIES)

ACINPUTASSY

SLO-BLOW

FUSE

BATTERY LIFE EXPECTANCY: 10 MINUTES @ 250V (AFTER POWER DOWN)

Figure 3-53.

H7112 Memory Battery Backup Power Supply — Interior View

3-78

OFF/ON

SWITCH
TK-0450

Electrical Characteristics
The H7112 battery charger circuit is comprised of the following:
An ac input assembly
Rectifier
Bias voltage supply

Fast/slow charger

Battery-out circuit
Emergency shutdowncircuit.

Figure 3-54 is a simplified electrical schematic of the charger.
AC Input Assembly
The AC input assembly (Figures 3-53 and 3-54) consists of an ac input cable with plug, a 4-pole, 2position ON/OFFtoggle switch, S1, a slo-blo fuse, F1, a barrier strip used in changing from 120 to 240
Vac, constant-voltage transformer, T1, and output connector Pl. This entire assembly is replaced
when going from 120 Vac to 240 Vac operation, or vice versa.
The following circuits are on the 5412675 PC board of the H7112.
Rectifier
The low-voltage ac from T1 is fed to the rectifier bridge via connector P1/J1. The voltage developed
across capacitor Cl is 50 to 70 Vdc.
Bias Voltage Supply

This circuit provides the +15 vdc bias voltage for the various control circuits in the H7112.
Fast/Slow Charger

The charger operates as a constant-current source. Whenthe batteries reach a 90 percent charge stage,
the fast/slow charge circuit switches automatically to a trickle charge that is maintained until the
battery is needed for power down or powerdip situations. While the H7112 is operating in its fastcharge state, a LED is turned on, being visible through the top louvers of the cover. Charge rates for

two modes are 500 mA and 10 mA, respectively.

Battery Out Circuit
If an outage occurs, the generation of an automatic ACLOsignal by the H7100 powersupply causesa
transistor switch to turn on, supplying the full battery voltage (36 Vdc) to the H7102 and H7103
regulators of the H7100 power supply. The H7102 normally supplies +12 Vdc at | to 10 A; the H7103
provides +5.0 Vdc at 2 to 20 A and -5.0 Vdc at 0 to 0.20 A.
The corresponding power available under battery backupis:
From H7102: +12 Vdc at 4.6 A
From H7103: +5 Vdc at 18.5 A, and -5 Vde at0.2 A
A sensecircuit on the BATT OUTline monitors the dc voltage at the input to the regulators of the
H7100 de powersupply so as to ensure that initial dc voltage is available. An AC OKsignal (-12 +3
Vdc) is sensed and, when AC LOisasserted (AC OK goes to ground), the battery takes over and
supplies dc voltage to the regulators.

Whentheinitial voltage level of the battery at takeover (approximately 40 Vdc) has decreased to 27 V,

the battery voltage low-sense circuit disconnects the batteries to protect them from deep discharge.

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If the DEC powercontrol bus senses a thermal problem, it will inhibit the battery output voltage by
connecting pin 2 of either J10 or J11 to ground (EMERGENCY SHUTDOWN- refer to Paragraph
3.2.1, Power Control Bus).
In series with a relay coil (not shown in the schematic) is a set of contacts on the ON/OFF switch (S1)

and two pins on the BATT OUTconnector J7. If the ON/OFF switch is in the OFF position, or if

closure of the relay is not provided across pins 3 and 6 of J7 (AUX SW), no battery charging or battery
out voltage is available.
|
To charge the batteries when the H7112 is out of the system, the following steps must be taken.
1.
2.

Onthe interface (BATT OUT) cable, pin 3 must be jumpered to pin 6 and pin | to pin 8.
The H7112 must be plugged into a properac outlet.

The ON/OFFswitch (S1) must be set to its ON position.

Emergency Shutdown
If a thermal problem developsin the 11/780 system, a ground is asserted between J2 and J3 (Figure 354), thereby turning off the transistor switch in the BATT OUTline.
CAUTION
An important consideration in storage of the DEC
12-12499-00 lead-acid battery is its storage temperature. With storage temperatures above 18.5° C (65°
F), the acceptable storage period falls off significantly, becomingas short as 6 months at 35° C (96°
F).
3.4.2.2 H7111 Time-of-Day Clock (TODC) Battery Power Supply - The H7111 is comprised of the
following:
1.
2.

A constant-current, dual-rate battery charger
One 12 V, 5 A/hr, sealed lead-acid battery (DEC P/N 12-12499-00).

Whenfully charged, the battery will supply 5 Vdc at 25 mA forat least 100 hours. Recharge timeis less
than 24 hours. For other H7111 performance specifications refer to Table 2-8.
Mechanical Configuration
The H7111 (Figure 3-55) is housed in a rack-mountable cabinet that is side and top ventilated by
natural convection through louvers. The cabinet weighs approximately 2.25 kg (5 lb) and has the
following dimensions:
Height - 8.9 cm (3.5 in)
Width — 48.3 cm (19 in)
Depth — 10.2 cm (4.0 in).

Primary powerfor the H7111 is supplied by the controller of the main cabinet(refer to the AC Power
Distribution System of Figures 3-10 and 3-12). The +5 Vdc, BAT DC LO, and GND outputsare sent

to the TODC, but the +12 Vdc outputis for test only.

3-81

12V
BATTERY

Figure 3-55

ON/OFF SWITCH
FUSE
(1/8A, SB)

H7111 Time-of-Day Clock Battery Power Supply

3-82

TK-0457

Electrical Characteristics

CM AMADMNRWNS

Dual-Rate Battery Charger
The charger (see the simplified electrical schematic of Figure 3-56) comprises:
Input cord and plug assembly
Stepdown transformer
Bridge (full-wave) rectifier and filter
Trickle charge circuit
Fast charge circuit
Charge level control circuit
Battery low-voltage detector
Battery low-voltage disconnect relay
5 V regulator
Battery DC LO generator.

Input Cord and Plug Assembly
The 1.1 m (3.5 ft) 3-wire line cord connects to the transformer at an input terminal board.
Stepdown Transformer
The stepdown transformer (120 Vac or 240 Vac primary, depending on the system installation) supplies approximately 22 Vac, rms.
Rectifier and Filter
The solid-state bridge rectifier output is filtered by a 1900 uf capacitor whose size maximizes the
average dc output. A 2.2 KQ, | W resistor serves as a bleeder and, in the event that fuse protection is
lost, as a load.

Trickle Charge Circuit

Thetrickle charge circuit uses a zener diode/transistor combination as a current source providing a 10
mA trickle current to the battery and 22 mA to the H7111 control circuits.

Fast Charge Circuit
The fast charge circuit also uses a zener diode/transistor combination to provide a 215 mA charging
current to the battery.
Charge Level Control Circuit
The charge level control circuit controls only the fast charge current source, turning it on or off as
required. When battery voltage reaches 14.6, which represents a 90 percent chargestate, the fast charge
current source turns off. Turn-on reoccurs whenbattery voltage falls below 13.0 Vdc. At powerup, the
unit always starts up on fast charge.
Battery Low-Voltage Detector
The purpose of the battery low-voltage detector is to protect the battery by disconnecting it when
terminal voltage falls below 10.5 Vdc. Operation assumesthat no line voltage is present; otherwise,
discharge would not have occurred. Detection of the 10.5 Vdc level causes closure of a transistor
switch in the low-voltage detector circuit. Switch closure opens the coil circuit of a battery-disconnect
relay. Relay unlatching disconnects the battery from the fast charge circuit.
The battery then remains disconnected until primary poweris regained, fast charge comeson, and the
battery voltage rises to 11.6. At this point, the relay pulls in to reconnect the battery to the fast charge
circuit. The low-voltage detector uses a single transistor and one section of a 3-section LM339 com-

parator.

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3-84

Low-Voltage Battery Disconnect Relay
The battery disconnect relay is a very low coil current type usedas a latch. Its function was described
previously.
5 V Regulator
The purpose of the 5 V regulator is to provide the required +5 Vdc to the time-of-day clock during
poweroutagesor voltage dips, using the battery as its power source. The 3-terminal 7805 is used in the
H7111. This regulator has an internal current-limit feature and is heat-sinked by contact with the etch
on the H7111 PC board.
Since maximum load current is 25 mA, 7805 powerdissipation is very low. Diode buffering keeps the
trickle charge current source independent of load variations.
Battery DC LO Generator
Like the AC LO and DC LO signals generated by the H7100 dc power supply under power-fail conditions, the BATT DC LO generated by the H7111 goes to the CPU whereit is used in decision processes
relative to the loss of +5 Vdc for the TODC. BATT DC LOis generated by a p-channel FET thatis
turned on by one section of the LM339 3-section comparator and results from turn-off of the lowvoltage disconnect relay, and shorting of capacitor at the input to the comparator to effect its turn-off.
The FETis normally on until its gate is made 6 V more positive than the source for complete turn-off.
On power up, the charging time for the capacitor at the input to the comparator results in a 200 ms
delay before BATT DC LO goeshigh (refer to the timing diagram of Figure 3-57). BATT DC LO H is
+4 to 4.5 Vdc; BATT DC LO L 1s less than 0.4 Vdc.

VOLTAGE

|OFF
|

BATDCLO —+»

|
|

100 HOURS,

| MIN.

+12VDC

200

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5
0
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24 HOURS MA} |
XK

OFF,

NOTE 1
ASSUME BATTERY WAS FULLY

CHARGED (90% CAPACITY).

Figure 3-57

|
:

_/)

NOTE 2
FAST CHARGE MAY CYCLE UNTIL BATTERY CHARGE IS TOPPED OFF

AT ABOUT 125% CAPACITY.

H7111 Time-of-Day Clock Battery Power Supply — Timing Diagram

3-85

TK-0439

12 V Lead-Acid Battery (DEC P/N 12-12499-00)
The H7111 12-12499-00 battery is a 5 A/hr, sealed lead-acid type whose 6 cells deliver a terminal
voltage of 12 Vdc. As previously indicated, terminal voltage varies appreciably with battery charge
state: e.g., at 90 percent of full charge, voltage is 14.6; at full discharge, voltage is 10.5.
The H7111 is on fast charge mode at power up and wheneverterminal voltage falls below 13.0 Vdc.
Trickle charge replaces fast charge when voltage hasrisen to 14.6 (90 percent charge point). At 10.5 V,
battery state is “‘full discharge’’ and auto disconnect occurs.
CAUTION
Discharge to less than 9 Vdc can cause permanent
damageto the battery.
After one week on trickle charge, battery voltage will level off at 14.2, the battery then being at
approximately 120 percent charge.
CAUTION
An important consideration in storage of the DEC
12-12499 lead-acid battery is the storage temperature. With storage temperatures above 18.5° C (65°
F), the acceptable storage period falls off drastically,
becoming as short as 6 monthsat 35° C (96° F).
3.4.3. Power-Failure Provisions in the H7100 DC Power Supply
The power-failure provisions incorporated in the H7100 are as follows.
Front-panel status indicators providing visual indication of:

eon of

POWER NORMAL condition
Plug-in regulator failure

Overcurrent condition

Overvoltage condition
Powerinverter failure.

A reflective indicator for an overtemperature condition within the supply.

AC LO and DC LO outputs to the CPU.

An OVERTEMPERATURESENSE signal for the power controller.

Power Normal
Whenlit, the POWER NORMAL lampindicates that all dc outputs from the H7100 are normal. For
this condition to exist, the other four status lamps must be unlit; i.e., there can be no regulator failure,
no overcurrent condition, no overvoltage condition and the powerinverter must be functioning normally.
Plug-In Regulator Failure
Whenlit, the PLUG-IN REGULATOR FAILURE lamp, merely indicates that one of the plug-in
regulators is malfunctioning; since it does not indicate which one, the operator must perform instrument checksto isolate the defective board.

3-86

Overcurrent
The overcurrent lamp lights when the load current of the +5.1 Vdc supply rises to 120 A. It does not
indicate overcurrent conditions existing on other H7100 dc outputlines. Pulsing is stopped when the
120 A limit is exceeded.
Overvoltage
The overvoltage lamp lights when the regulated +5.1 Vdc voltage malfunctions and produces an
output reaching 6.2 or more Vdc. Whenlit, this lamp also indicates that the crowbar hasfired, a
condition that causes the H7100 to turn off. However, automatic reset occurs after approximately 100
ms and, if overvoltagestill exists, the overvoltage lamp will reilluminate. This cycle will repeat itself
until the power supply circuit breaker is set to OFF.
Power Inverter Failure
Whenlit, the POWER INVERTER FAILURE lampindicates a hardware failure on the H7100
motherboard. Under battery backup conditions, this lamp will remain lit, but in this case a power
inverter failure would be unlikely since the power-fail condition preceding battery backup would not
produce inverter failure.
Overtemperature
The overtemperature lampis a reflective indicator that illuminates when the 100° C sensor on the heat
sink for the outputrectifiers turns on. Note that sensor output is fed to controller via a 2-wire cable
leading from parallel-wired connectors J4 and J5 on the rear panel of the H7100 supplies (Figure 3-41).
J4 and J5 connect with TOTAL SHUTDOWNconnector J9 at the rear of the 869 controller or with
daisy-chained J1 and J3, the power control bus connectors, on the 866 controller. In the latter case, the

overtemperaturesignal will shut down all power supplies on “‘switched”’ power, but the memory power
supply, blower number 2 (adjacent to the memory card cage) and the battery backup powersupplies
will remain energized. The overtemperature sensor on any powersupply can initiate shutdown of the
entire system (or the switched loadsin the case of the 866 controller), but cannoteffect direct shutdown
of the power supply in which they are located. If an overtemperature condition occurs, the dc input
from the H7112 memory battery backup power supply automatically disables.
AC LO and DC LO

These outputs, initiated on the bias/control board of the H7100, are transmitted to the CPU so that

suitable power-fail sequencing can be effected to cope with a sensed imminent power-fail situation. AC
LO (i.e., AC LO deasserted) is -9 Vdc. Whenasserted (failure imminent) AC LO goes to 0 Vdc. DC
LO has the same signal levels as AC LO.

3.4.4 Power Controller Overtemperature Sensor
Each of the DEC standard powercontrollers used in VAX-11/780 systems incorporates an ambientair overtemperature sensor. The sensor is mounted on theleft side of the controller chassis in the 866
and at the rear of the chassis in the 869 (to the right of the total shutdown connector, J9, as seen from

the rear of the chassis). In all cases a small (3/4 in diameter) cutout exposes the sensor to ambientair in
the vicinity of the controller; e.g., Figure 3-15.

In the 866 controllers, activation of the overtemperature sensor causes shutdown of all devices on
switched power only. In the 869 controllers, activation of the overtemperature sensor causes a total
shutdown of the cabinet in which the particular controller is located, operating independently of the
powercontrol bus. Thus, cabinets other than the one experiencing the overtemperature can continue

to operate.

3-87

3.4.5 Air Flow Sensors
Eachof the impeller-type blowers in the main cabinet (normally three blowers) and the single blowerin
the SBI cabinet (Figure 3-3) has an associated air flow sensor unit. The location and operation of these
sensors was discussed earlier (869D Controller). In Figure 3-11, the air flow sensors are shown as AFS
1 through 3.
NOTE
The air flow sensor control box (7015036) that provides +15 Vac for sensor actuation is the same as the
air flow interface shown in Figure 3-22. This unit is
not required with the 869 controller because the +15
Vdc is provided byit.

3.55 CABLING
VAX-11/780 main cabinet cabling falls into three basic areas:
AC interconnections
Powercontrol signal interconnections (e.g., PCB, OT, AFS)
Backplane dc interconnections.
Data cables are not covered in this power systems manual.
3.5.1 AC Interconnections
Sheet 1 of Figure 3-7 illustrates the cabling configuration of the VAX-11/780-C/D main cabinet. The
item numbers on this sheet are explained in the tables provided by sheets 2, 3, and 4. For each item
these tables show the associated part number, item description, and “‘from-to” cable locations. Three

tabulations are given CA/DAfor 115 Vac, 60 Hz; CB/DB for 230 Vac, 50 Hz; and CC/DC for 115
Vac, 50 Hz.

In Figures 3-19 and 3-21 (rear views of the 866D and 866E powercontrollers), the 120 V (866D) or 240
V (866E) duplex outlets are identified as J9 through J15; with the exception of receptacle polarization,
the backpanel configurations of the two controllers and the loads assigned to each receptacle are
identical. The single-line diagram of Figure 3-10 shows the ac powerdistribution for systems using the
866 controller. Figure 3-12 shows the same distribution for the 869 power controller.
Referring again to sheet | of Figure 3-7, the loads connected to the power controller are:
1.

Six H7100 dc power supplies (although space for 6 supplies is provided, the actual number
used will varywith the particular system configuration. In the minimum “C”’ configuration,
only 3 H7100s are used; in the ““D”’ configuration, 4 H7100sare used. If the FP780 option is
included in either configuration, an additional supply is provided for it. Thus, in VAX11/780 systems presently available, a maximum of 5 H7100s will be used.)

Three impeller-type blowers (numbers 1, 2, and 3)

11/03 microprocessor

H7111 TODC battery backup powersupply

H7112 memory battery backup power supply (optional)

RX0O1 floppy disk

7015036 air flow sensor control box(air flow interface).

3-88

The 11/03 and RXO1 have integral power supplies that are powered through the 866 controller.
3.5.2. Power Control Signal Interconnections
In an overview sense, the power control signal interconnections provide:
1.

Bus connections from power controller connectors Jl and J3 to the individual overtemperature output connectors (J4 and J5) on each power supply rear panel; these connectors are daisy-chained from supply to supply.
Bus connection from the power controller (connector J3) to the System Control Panel (SCP)

at the top front of the main cabinet.

Overtemperature bus connection from the H7112 memory battery backup power supply
(connector J1) to PS No. 2 (connector J5).

SCP connection to the RXO1 floppy disk.

Air flow sensor power connection to the air flow sensor control box and control signal
connection from sensor to power controller via the power control bus.

3.5.3 Backplane DC Interconnections
Drawing D-IC-11780-0-3 of the print set details the dc interconnections between:
1.
2.

The de power supplies and the logic modules.
The RXO1 floppy disk, SCP, and KA780-A CPU.

Sheet 2 of the referenced drawings provides item descriptions and cable termination data similar to
that provided for Figures 3-7 and 3-8 of this power system manual.
A quick-reference, single-line diagram showing these power supply to logic module connections is
given in Figure 3-37. Also shownin this diagram are voltage and current characteristics for each load.
3.6 GROUNDING
The only grounding external to the main cabinetis for the disk drives (RP05/06, RK06 or RM0O3). The
required cablesare installed as part of the system installation (VAX-11/780 System Installation Manual, EK-SI780-IN-PRE).
To verify that the prescribed grounding has been accomplished, see that:
1.

The first disk drive of daisy-chained drive complements is connected to the main frame by
DEC 25 ft standard ground connector.

The second drive of the daisy chain is connectedto thefirst drive by a 3 ft standard ground
connector.

All subsequent drives of the daisy chain are similarly connected as in step 2.

Refer to Figure 3-58 for details.
The material in Appendix A extracted from the DIGITAL Site Preparation Guide is provided to show
the importance of, and DIGITAL’s basic approach to, the grounding of computerinstallations.

3-89

MAIN CABINET

FIRST DRIVE

(A) MAIN CABINET TO FIRST DRIVE

GROUND STRAP FROM

PREVIOUS DRIVE

GROUND STRAP TO

NEXT DRIVE

TK-0592

(B) ALL DRIVES BETWEEN FIRST AND LAST

Figure 3-58

Grounding Details for RPO5/06 Disk Drives

3-90

CHAPTER 4
H7100 DC POWER SUPPLY
FUNCTIONAL SECTION DESCRIPTIONS
4.1

GENERAL

Physically, the H7100 power supply comprises:
1.
2.
3.
4.
5.
6.
7.

Frame
Front panel (ac input adapter)
Middle panel
Motherboard
Rear panel

Plug-in bias/control board

Two plug-in regulator boards (optional).

The system description of Chapter 3 covers these elements. The block diagram level discussion of
Chapter 4 provides functional details of the motherboard, bias/control board, regulator boards, and
the associated discrete components mounted on the middle panel and rear panel. Note that when the
H7100 is installed, its motherboard is vertically oriented along the left side of the supply. The plug-in
boards connect with the motherboard throughjacks J1, J2, J3, and J4 (refer to the connector location
diagram of Figure 4-1). The status board (described in Paragraph 3.4.3, Power-Failure Provisions in
the H7100 DC Power Supply) connects to the sensing circuits on the bias control board via a ribbon
cable (Figure 4-2). Figure 4-3 is the interconnection wiring diagram for the H7100.
In the system description (Chapter 3), the H7100 dc power supply was discussed under headingof its
functional sections. Since the following block diagram description is keyed to the physical breakdown
(front panel, middle panel, motherboard, rear panel, bias/control board and regulator boards) of the
supply, a few points regarding their functional/physical relationships are in order.
First, consider the basic H7100 power supply with its single (+5.1 Vdc) output. Primary power from
the single-phase input connector on the front panel reaches the raw dc supply (MB1) via connector
P1/J8 at the top right corner of the middle panel (viewed from the front of the supply). Figure 4-1
shows the connector and the 7-point terminal board J6 on the motherboard supplying 120 or 240 Vac
to the rectifier/filter components comprising the raw dc supply section. After the dc-to-ac inverter has
converted the +150 Vdc output of the raw dc supply to 20 kHz ac, the pulse output is fed to output
transformer T1 on the rear panel. Therectifier, filter, snubber network, voltage sense, and current
sense circuits are also located on the rear panel. The current and voltage sense outputs from the +5.1
Vdc output section are then fed to the +5 Vdc 100 A regulator circuits on the bias/control board
(Figures 4-3 and 4-7). Details of regulator operation are given under Paragraph 4.6 (bias/control
board).
The same transformer (T1) providing the 5.1 Vdc output provides the ac outputs for the F30 and +30

Vdcrectifiers and filters located on the motherboard.

The bias/control board carries the bias/control power supply, which generates regulated +12 and +5
Vdc as well as -12 Vdc unregulated for use by the power supply control circuits.
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4-8

The bias/control board also incorporates protection and status circuits (Figure 4-7). All status signals
except AC LO energize the status indicators on the front panel. These signals leave the B/C board via
connector P3/J2 (Figure 4-1).
As shown in Figure 4-1, the H7102 (+12 VB) regulator interfaces with the motherboard via 24-pin
connector J2. Connector J1, which is parallel-wired with J2 (Figure 4-3) accepts either the H7101 (-5.2
Vdc) or H7103 (+5 VB) regulator board. The B designation indicates that the board has battery
backup capability (Paragraph 4.7.1, H7103 Regulator).

OA BR WN =

4.2 FRONT PANEL (AC INPUT ADAPTER)
As seen in Figure 3-35, the front panel (ac input adapter) is comprised of the following.
AC input connector, Jl
Battery adapter, J2
Single phaseline filter
2-pole, 20 A ac circuit breaker, CB1

Status card with ribbon connector J1/P2.

Figure 4-4 is a simplified block diagram showing the powerflow from input connector J1, through the

line filter and circuit breaker to connector P1/J8 located on the middle panel. Also shownis the AC
LO line from the AC LO circuit (BC24) on the bias/control board. The function of this line is dis-

cussed in Paragraph 4.6 (bias/control board).

Two front-panel (ac input adapter) configurations are available for the H7100 - one for 120 Vac and
one for 240 Vac controller outputs.

4.3

MIDDLE PANEL

Also shownin Figure 4-4 are the components mounted on the middle panel:
1.
2.
3.
4.

Connector P1/J8 (projects through the panel)
Fuse Fl, a 1/8 A, slo-blo (on the panel backside)
Relay K1 (panel backside)
3 ohm inrush limiting resistor (panel backside).

As shown in the interconnection diagram of Figure 4-3, primary poweris provided to the motherboard
raw dc supply via P1/J8. Relay K1 is energized by a 24 Vdc, 100 mA signal from relay driver BC32 on

the bias/control board (refer to Paragraph 4.6).
4.4

MOTHERBOARD

OW NANDWNEWNS

The motherboard (refer to the block diagram of Figure 4-5) comprises the following circuits:
Start-up and ac sense transformer
Raw dc supply
Power switch and base drive transformer
Snubber networks
Reset diodes
Raw dc sense
Crowbar

+30 Vdc rectifier/filter section
Floating 30 Vdc rectifier/filter section.

4.4.1 Start-Up and AC Sense Transformer
This transformer steps down the 120 or 240 Vac to 12 Vac for use in power supply start-up and for ac
line monitoring after start-up.

4-9

STATUS CARD
FRONT PANEL

MIDDLE PANEL

> CD GD

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90-127V
50-60 Hz
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TO T.B. J6-1

120 OR 240 VAC
TO T.B. J6-4
ON M.B.

12 VAC @ 100 mA
FROM RELAY DRIVER
(BC32) VIA P5/J5
ON MB

SINGLE
PHASE
LINE
FILTER

ooON

—_

Figure 4-4 H7100 Front Panel/Middle Panel Block Diagram

4-10

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AC LO

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4.4.2 Raw DC Supply
The raw dc supplyis the source of the +150 Vdc used by the inverter. With 120 Vac input, the raw dc
supply functions as a voltage doubling rectifier; with a 240 Vac line, the supply is connected as a
fullwave rectifier. Large (4500 uF) capacitors provide storage for powerline ride-through.
4.4.3 Power Switch and Base Drive Transformer
The power switch controls the main flow of power through the power supply by delivering a variablewidth pulse to the power transformer. Fourtransistors, all turned on (or off) simultaneously, connect
the power transformer to the dc source during the pulse. Base drive is achieved by means of a second
transformer, whose inductive energy triggers on the bases of the four transistors. Emitter currents in
two of these transistors couple more base drive energy through this transformer for the remainderof
the pulse. Four fusible link resistors protect the transformer against overload.
4.4.4 Snubber Networks
Twoidentical snubber networks, each consisting of a capacitor in series with a parallel resistor/diode
combination, divert inductive current from each of the two pairs of powertransistors during turn-off.
4.4.5 Reset Diodes
The reset diodes provide a path for the inductive current stored in the power transformerafter the
power switch has turned off. The inductively stored current forces the polarity of the transformer to
reverse until all the stored energy is returned to the raw dc supply. Polarity reversal time is equal to
pulse time.
4.4.6 Raw DC Sense
The raw dc sensecircuit measures the raw dc (£150 V) and comparesit to a reference voltage. When
the raw dc increases to 225 Vdc, a low signal is producedat J3 to turn on the power supply. When the
raw dc decreases to 175 V, this signal goes high and the powersupplyis turned off. This circuit floats at
a -150 Vdclevel. A resistor/diode combination provides the +15 Vdc required for operation of the
raw dc sensecircuit.
4.4.7 Crowbar
The crowbarprovidesa short circuit across the +5 Vdc output wheneverthis output exceeds 6.3 Vdc.
A sense signal is provided to the crowbar detector (BC22) on the B/C board to shut off the power
supply when the crowbarfires.
4.4.8 +30 Vdc Section
In the +30 Vdccircuit a power pulse from the power transformer is LC-filtered to 30 Vdc nominal.
Under no-load conditions, a resistor holds this voltage below 50 Vdc. When either regulator cardis
pluggedin, the filter capacitor is automatically connected. The +30 Vdc negative returnis tied to the
+5 Vdc return.
4.4.9 Floating 30 Vdc Section
The floating 30 Vdc section operates in the same wayas the +30 Vdcsection, but is wired as a negative
output. Since neither output is referenced to ground, this section can be used foreither positive or
negative regulators.
4.5 REAR PANEL
Figure 4-6 is a block diagram of the circuitry on the rear panel of the H7100. The principal component
on the rear panelis the output transformer, T1. When energized by the 300 V (peak) 20 kHz pulsetrain
from the dc-to-ac inverter on the motherboard, this transformer provides low voltage outputs for the

+5.1 Vdc rectifier and filter located on the back panel, and for the two 30 V rectifier/filter sections

located on the motherboard.

4-12

FROM J1/P7 ON H7103 (+5 VB)
-—K< OPTIONAL REGULATOR BOARD
INSTALLED AT J1/A

FROM J1/P9 ON H7101
(—5.2 V) OPTIONAL REGULATOR
BOARD AT J1/A
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OF APPENDIX
|

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MOTHERBOARDVIA T.B. J7-1/2.
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Figure 4-6 H7100 Rear Panel Block Diagram

4-13

TK-0586

The temperature sensor (located on the +5.1 Vdc output diode heat sink mounted below output
transformer T1 on the back panel) receives +15 Vdc from line 2 of the DEC power control bus. When
the design temperature of 100° C (212° F) for sensor closure is reached, emergency shutdown is
generated on the power control bus when sensor closure grounds the +15 Vdc overtemperaturesignal.
As seen in Figure 4-6, the AC LO and DC LOsignals from corresponding circuits (BC24 and BC25) on
the bias/control board are fed to the CPU through backpanel connector J3 for use in power-fail
sequencing.
Connectors J6 and J7 are never used together. Connector J6 is used with the H7101 (-5.2 Vdc) regulator board, and J7 with the paired battery backup boards, H7102 (+12 VB) and H7103 (+5 VB). The
connector used is inserted in a backpanel rectangular cutout (Figure 3-31). Figure B-1 shows the
cabling configuration from regulator boards to output connector, and the connection to the battery
backup power supply used with the H7102/H7103 board combination.
The +5.1 Vdc, 100 A output is parallel-wired to 5 positive (red) output terminals and 5 negative
(black) return terminals. The back of the output connector box provides the mounting surface for the
two 15,000 uf output capacitors of the +5.1 Vdc supply.

4.6

BIAS/CONTROL BOARD

The circuits on the bias/control board can be functionally divided into three principal elements (refer
to the block diagram of Figure 4-7).
1.
2.
3.

Bias/control power supply
5.1 Vdc, 100 A regulator circuitry
Protection and status circuits.

The 5.1 Vdc, 100 A regulator was functionally described in Paragraph 3.3.2 (power generation — H7100
dc powersupply). Paragraph 4.6.1 describes the functional composition of the basic H7100 regulator.
The bias/control power supply section of the bias/control board provides regulated +5 Vdc and +12
Vdc as well as unregulated -12 Vdc for the H7100 control circuits and LEDs.
As the name implies, the protection circuits (e.g., I sense, crowbar sense, etc.) generate signals that
protect the supply from destructive malfunctions, but do not provide visual indications of the condition. The status circuits provide front-panel indications of power supply status (Paragraph 3.4.3 power-failure provisions in the H7100 dc powersupply).

—,

SO eNIANR WN

4.6.1 Bias/Control Power Supply
The bias/control power supply (Figure 4-7) comprises:
Snubber-suppressor (BC1)
Bias power switch (BC2)
+12 V bias supply (BC3)
+5 V bias regulator (BC4)
Bias power switch driver (BCS)
Bias control amplifier (BC6)
Bias ramp generator (BC7)
20 kHz bias clock (BC8)
Bias pulse width modulator (BC9)
Start-up supply and ac monitor (BC10).

4.6.1.1 Snubber-Suppressor (BC1) - The snubber-suppressorprotects the single-transistor bias power
switch (BC2) during turn-off by diverting inductive currents away from the transistor and limiting the
maximum voltage caused by any ringing to a safe value.

4-14

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4.6.1.2 Bias Power Switch (BC2) - The bias power switch controls the main powerflow into the £12
V bias power supply by changing the inductance of the flyback transformer’s primary winding.
4.6.1.3 +12 V Bias Supply (BC3) - The +12 V bias supply is the basic source of the voltages (+ 12,
—12, and +5) required for H7100 control and for its LED indicators. When thetransistor switch for
bias power (BC2)is off, two diodes (one in each leg of the flyback transformer’s secondary) discharge
the transformer-stored energy into the output capacitors and loads. These diodes are reverse biased
whenthe transistor switch is on and the flyback transformer is charging. Signals for drive turn-off and
transistor-switch hold-off are provided for the power switch driver (BCS).
4.6.1.4 5 V Bias Regulator —- An LM340T-5 3-terminal regulator uses the +12 V output from the bias
supply to produce +5 V at 0.25 A for the H7100 internal logic circuits and LEDs.
4.6.1.5 Power Switch Driver (BCS) - The power switch driver is energized by a variable-width pulse
from the bias supply pulse width modulator (PWM) (BC9) and drives the bias powerswitch transistor
through the power switch driver transformer. When the driver switch transistor is off, the bias power
switch transistor (BC1) is triggered by the inductive energystored in the driver transformer and driven
by the current through its secondary windings. Whenthe driver switch transistor is driven on, the bias
power switch transistor is turned off. A forward-biased diode holds the driver switch transistor on
until the energy in the flyback transformer of BC3 is depleted.
4.6.1.6 Bias Ramp Generator (BC7) - The bias ramp generator accepts a variable ramp voltage
(above 5.7 V) and produces a ramp waveform of fixed amplitude and variable ramp time. The precision reference for comparison with the input ramp voltage is also generated here.
4.6.1.7 Bias Clock (BC8) - The bias clock produces a 20 kHz rectangular waveform that establishes a
maximum pulse width. This signal synchronizes the bias supply and provides a clock output to sync
the main +5.1 V supply and the plug-in regulators.
4.6.1.8 Bias Pulse Width Modulator (BC9) - The bias pulse width modulator accepts 20 kHz clock
pulses from BC8 and a variable width ramp input from the ramp generator (BC7) to produce rectangular waveform with variable pulse width to drive the power switch (BC2).
4.6.1.9 Start-Up Supply/AC Monitor (BC10) - During initial power up of the H7100, 12 Vac from
the start-up transformeris rectified by the start-up supply/ac monitor circuit to produce +11 Vdc.
This voltage energizesall of the bias supply circuits and pulses the transistor switch of the power switch
(BC2) to power up the 12 VA flyback power supply. When the output of this supply reaches 10.5 V,
normal operation is possible and the ac input to the start-up supply/ac monitor is unloaded. The
unfiltered, rectified ac waveform is used to measure line voltage to determine AC LO at BC24.

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4.6.2 +5.1 V, 100 A Regulator
The +5.1 V, 100 A (main) regulator comprises (Figure 4-7):
The feed-forward circuit (BC11)

+5.1 V/100 A control amplifier (BC12)

Ramp generator (BC13)
20 kHz clock (BC14)
Pulse width modulator (BC15)
Control switch (BC16)
Power switch driver (BC17)
Turn-off-drive buffer (BC18)
Reset sense circuit (BC19)
Power-switch fail detector (BC20)

5 V/100 A overcurrent detector (BC21)

Crowbardetector (BC22)
Peak primary overcurrent detector (BC23).
4-18

4.6.2.1 Feed-Forward Circuit (BC11) - The feed-forward circuit peak-detects the 150 V (nominal)
pulses from the power transformer (T1) on the rear panel. This input, referred to as “‘turn off drive’”’
Originates at one leg of the 30 V winding. Since the detected peaks are proportional to line voltage, the
output is a dc current proportional to line voltage; e.g., at 120 Vac this current is 130 yA.
4.6.2.2, 5 V/100 A Control Amplifier (BC12) —- The 5 V/100 A control amplifier compares the +5.1 V
output (nominal) of the H7100 supply with a precision reference generated by the ramp generator
section (BC13) and a voltage from the slow run-upcircuit (BC30). R/C feedback circuits control the
frequency response of the regulator loop. When the feedback signal (from the ramp generator) is
negative, the power supply is off. The output of the control amplifier is a current whose magnitude
depends upon a combination of line and load conditions.
4.6.2.3 Ramp Generator (BC13) - The ramp generator accepts variable-current inputs from the feedforward (BC11) and control amplifier (BC12) circuits, adds them, and produces a ramp waveform of
fixed amplitude and variable ramp time. This section also includes the circuit for the 5.130 V reference
that determines the output voltage.
4.6.2.4 20 kHz Clock (BC14) - The 20 kHz clock produces a rectangular waveform whose positive
portion determines the maximum pulse width for the powerstage. A signal from the bias/control clock
(BC8) synchronizes the two clocks.
4.6.2.5 Pulse Width Modulator (BC15) - The pulse width modulator synchronizes ramp generator
output with the negative edge of the clock pulse waveform to produce a rectangular waveform whose
pulse width is equal to the ramp time. Inputs to the NE555 timer of the PWM circuit from the crowbar
sense or switch I sense will cause pulsing to cease under overvoltage or overcurrent conditions.
4.6.2.6 Control Switch (BC16) - The control switch provides a positive output when the clock signal
is low, when a low is received from the reset sense circuit (BC19), and during turn-on from thestart-

up/ac monitor (BC10).

4.6.2.7

Power Switch Driver (BC17) - The power switch driver amplifies the pulsed signal from the

PWMandcontrol switch and drives the main power inverter. When the transistor switch controlling

the drive to the main powerinverter is on, the powerswitches are off. When this switch is turnedoff,
energy in the transformer of the power switch (MB3) triggers the power stage and it turns on.

4.6.2.8 Turn-Off-Drive Buffer (BC18) - The turn-off-drive buffer responds to a 150 V pulse from one
leg of the 30 V winding of the power output transformer on the rear panel by storing energy in a
capacitor. This energy provides a source of powerfor fast turn-off of the power switches. After capacitor discharge, current through a resistor provides energy storage in the transformer of the power
switch (MB3) to retrigger the power switches.
4.6.2.9 Reset Sense Circuit (BC19) — The reset sense circuit detects the negative portion of the turnoff-drive pulse from the 30 V winding of the output transformer when the powerswitches are off and
the transformer is reverse-biased and resetting. During reset, the switches are held off by the control
switch (BC16) through a connection to the start-up supply/ac monitor circuit (BC10).
4.6.2.10 Power-Switch-Fail Detector (BC20) — The power-switch-fail detector provides a logic low to
the status card whenever the power switches of MB3 are driven on and no pulseis issued from the

power transformer, a condition that only happens when the power switches are not working. This
failure condition is indicated by the red “‘powerinverter failure’ indicator on the H7100 front panel.

4.6.2.11 5 V/100 A Overcurrent Detector (BC21) - The 5 V/100 A overcurrent detector accepts a 50
mV/100 A voltage proportional to the 5 V load current, compares this voltage to a threshold
reference and produces an overcurrent signal (negative edge) when the threshold is exceeded. The
threshold is approximately 60 mV (120 A) with the output at 5 V, and 30 mV (60 A) with the outputat
0 V (short circuit).
4-19

4.6.2.12 Crowbar Detector (BC22) - The crowbardetector is a diode that isolates the timing circuit
from the crowbarcircuit (MB7). When the crowbarfires, the crowbar detector is pulled low (to 1 V).
4.6.2.13 Peak Primary Overcurrent Detector - The peak primary overcurrent detector receives a pulse
(from the switch I sense transformer T3 on the motherboard) that is proportional to the current in the
powertransformer (T2 on the motherboard) primary. The detector comparesthis signal with a reference and pulls detector output low when the 30 V (15 A peak) reference is exceeded.

CO PANAMNRWNH>

4.6.3 Protection and Status Circuits
The protection and status circuits (Figure 4-7) comprise:
AC LO circuit (BC24)
DC LO circuit (BC25)
~9 Vdc source (BC26)
Output DC LO detector (BC27)
Regulator-fail gate (BC28)
Run-up reset buffer (BC29)
Slow run-up circuit (BC30)
Initial turn-on and delay circuit (BC31)
Relay driver (BC32).

4.6.3.1 AC LO (BC24) - The AC LO circuit accepts unfiltered full-wave-rectified ac from the start-up
supply/ac monitor (BC10). An LM301 op amp in the AC LO circuit compares the ac peaks to a
reference from the ramp generator BC13) of the +5.1 V, 100 A regulator and producesa train of pulses
at twice the powerline frequency. When the ac peaks are above the reference level (90 Vac input), op
amp output to a 9601, 15 msdelay, 1-shot multivibrator stretches the pulse train to a dc level that turns
the AC LO output transistor off, causing AC LO to go to -9 V (1.e., AC LO 1s deasserted).
4.6.3.2 DC LO (BC25) - Whenall three logic inputs to the DC LOcircuit are low,a logic high is
producedfor the status card and the AC LO outputtransistor turns off, allowing -9 V at DC LO (DC
LO deasserted). The three logic inputs to the DC LO circuit are the output DC LO detector (BC27),
regulator-fail gate (BC28) and initial turn-on and delay (BC31).
4.6.3.3 -9 Vde Source (BC26) - The zener regulator of the -9 Vdc source circuit provides the -9 Vdc
for AC LO and DC LOoutputs.
4.6.3.4 Output DC LO Detector (BC27) - The output DC LO detector is an LM339 comparator that
provides a low output whenever the 5 Vdc busrises above 4.75 Vdc.
4.6.3.5
Regulator-Fail Gate (BC28) - The regulator-fail gate produces a logic high when the +12 Vdc
OK inputis pulled low, indicating a failed plug-in regulator card. The logic high output of BC28 is
supplied to the DC LOcircuit (BC25) andthe status card (via J2/P3) on the bias/control board, the

ribbon cable, and J1/P2 on the status board.

4.6.3.6

Run-Up Reset Buffer (BC29) - The run-up reset buffer produces a logic high that initiates

slow run-up through BC30 and the 5 V/100 A control amplifier (BC12) if the crowbar (MB7)fires or
the peak primary overcurrent detector (BC21) is activated.

4.6.3.7 Slow Run-Up Circuit (BC30) - The slow run-up circuit accepts logic signals from the run-up
reset buffer (BC29) and the initial turn-on and delaycircuit (BC31). With either input high, the output
diode of the slow run-upcircuit is held negative. When both inputs are low, a capacitor charges slowly
until the slow-run-up output diodeis reverse-biased, allowing the precision reference voltage to determine output voltage.
4-20

4.6.3.8 Initial Turn-On and Delay Circuit (BC31) - The initial turn-on and delay circuit accepts a low
signal from the raw-dc sense circuit (MB6) and producesa logic low output after a delay of approximately 100 ms.
4.6.3.9 Relay Driver (BC32) — The relay driver accepts a logic low from theinitial turn-on and delay
circuit and produces +12 Vdc at 100 mAto drive the inrush relay (K1) whose other terminal is a -12
Vdc. Closure of the relay shorts out the 3 ohm inrushresistor located adjacent to the relay on the back
of the middle panel.
4.7 REGULATOR OPTIONS
The regulator options for the H7100 dc power supply are:

1.
2.
3.

H7101 —-5.2 V at 30 A (54-12560)
H7102 —- +12 VB* at 10 A (54-12556)
H7103 —- +5 VB(+5 VB at 20 A; -5 VB at 0.2 A) (54-12558).

The H7101, H7102 and the +5 VB section of the H7103 use the switching regulator concept described
in Paragraph 3.3.2.1. Because of its low (200 mA) load current requirement, the -5 VB regulator of the
H7103 is a switching polarity inverter used in conjunction with a 3-terminal output regulator.

ODO NAARWN >

4.7.1 H7101 (-5.2 V) Regulator
As seen from the block diagram of Figure 4-8, the H7101 comprises:

10.
11.
12.
13.
14.

Base drive circuit
Powerswitch
Output filter
Overcurrent circuit
Error amplifier
Ramp generator
Pulse width modulator (PWM)
20 kHz clock
Turn-off-drive circuit
Flyback diode
DC OK circuit
Crowbar
Voltage reference
Slow run-upcircuit.

4.7.1.1 Base Drive Circuit - The base drive circuit consists of a pulse transformer and base drive
transistor whoseinputis controlled by the duty cycle control signal from the pulse width modulator.
Power for the H7101 regulator is unregulated -30 V from the 350 wh chokeof the floating 30 V supply
on the motherboard. Line protection is provided by a 15 A fuse at the input to the pulse transformer
secondary. A 1,000 uF filter capacitor is automatically connected to the 30 V source when the regulator is plugged into jack Jl (Figure 4-1). Sensing of pulse transformer input for the turn-off-drive
circuit of the H7101 regulator is accomplished at the primary of the pulse transformer.
4.7.1.2 Power Switch — The power switch consists of a balun transfomer and two powertransistors
that are switched by the pulse transformer output of the base drive circuit. The balun divides the
current equally between the twotransistors.
4.7.1.3

Output Filter - The output filter consists of a 25 wh choke and 15,000 uF capacitor.

*The ‘‘B” suffix indicates a battery backup capability.

4-21

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4-22

4.7.1.4 Overcurrent Circuit - Current limiting in the overcurrentcircuit is provided by two paralleled
resistors in series with the 25 wH chokeof the outputfiiter. This arrangement permits monitoring of
peak choke current (approximately 40 A peak-to-peak). The current through the two paralleledresistors and the voltage across them is triangular in shape and rides on the average dc output current. The
current limit for the -5.2 V outputis set at 36 A.
4.7.1.5 Error Amplifier — In the error amplifier, an LM301A op amp compares the sensed voltage
from the overcurrent circuit with the precision reference (—5.1 V).
4.7.1.6 Ramp Generator - The conversion of error amplifier output to a current level is accomplished
by the ramp generator. The error current charges a 1000 pF capacitor to generate the desired voltage
ramp (-6.8 V peak).
4.7.1.7 Pulse Width Modulator (PWM) - The 55 timer of the PWM provides the input for the base
drive transistor (Paragraph 4.7.1.1). Pulse width varies with error voltage over the range of 0 to 25 us.
Figure 4-9 is a timing diagram for the PWM. Whenthe clock pulse goes low, the PWM timer1s
triggered on and the 1000 pF capacitor starts charging. As shown in the diagram, base drive in the
PWM starts whenthe clock signal falls to zero and ends when the capacitor is charged to -6.8 V. If the
-5.2 V output increases abovethe precision reference level, the capacitor charges at a faster rate. Since
the clock pulse is fixed (25 us on and 25 usoff), base drive decreases proportionately with the increase
in -5.2 V output to return this voltage to normal.

-12V

Ov
-—12V

need

CLOCK OUTPUT

PWM OUTPUT

{
1

~6.8V

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!

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RAMP GENERATOR OUTPUT

30V_
ov

POWER SWITCH OUTPUT

34A
30A F<
26A

—- —

—

— — FILTER CHOKE CURRENT
t—
TK-0587

Figure 4-9

H7101 Regulator Timing Diagram

4-23

4.7.1.8 20 kHz Clock - The 20 kHz clock establishes the basic operating frequency for the -5.2 V
regulator. A series resistor and capacitor connected to the control voltage input of an E555 timer
provide for external sync by a signal originating at the clock (BC8) of the bias/control power supply on
the B/C board. When the clock pulse at the buffered output goes high, the pulse width modulator
(PWM) is triggered on.
4.7.1.9 Turn-Off-Drive Circuit - Rapid turn-off of the power switch transistors between conduction
and reset 1s effected by a series-connected diode, 10 ohm resistor and 0.1 wF capacitor connected
between the secondary and primary of the pulse transformer. When the power switchtransistoris
turned on, the capacitor is charging through the resistor. When the switch is turned off for the reset
portion of the cycle, the capacitor generates a large reverse pulse on the base of the transistors to
sharpen the turn-off transition.
4.7.1.10

Flyback Diode - A UES602 diode between the power switch and the LC outputfilter is

reverse-biased when the powerswitches are turned on. Whentheswitchesturn off, the flyback diodeis

forward-biased and permits energy stored in the outputfilter to flow through the load for the duration
of the reset interval.

4.7.1.11 DC OK Circuit - The DC OK circuit consists of a transistor switch and voltage divider.
Whenthe sensed dc at the overcurrent circuit approaches —4.95 V, the collector of the transistor goes
high to generate a -5 V DC OK output. This signal is wire ORed with the +12 V DC OK and +5 V
DC OK signals at the input to the regulator-fail gate (BC28) on the bias/control board (Paragraph
4.6.3.5). When any of these failure-indicator signals goes low, the resultant high from the regulator-fail
gate turns on the red Plug-In-Regulator-Failure lamp of the H7100 status display (Paragraph 3.4.3).
4.7.1.12 Crowbar — Load protection for the —5.2 V regulator is provided by two SCRsthat turn on
sequentially to apply a short circuit across the output when its voltage exceeds -6.5 V, maximum.
Under shortcircuit conditions, (crowbarfired) H7101 output voltage falls to -0.8 V until the crowbar

is turned off. If the main (power) switch transistors short circuit, the crowbar will turn on for this
malfunction as well and, in addition, the 15 A fuse at the input to the base drive circuit will blow.

NOTE
Protection against the application of an external
voltage to the output is not provided.
4.7.1.13 Voltage Reference - The precision voltage reference for the LM30IA error amplifier is provided by a 1/4 M5.1AZI1 (5.1 V, 1 percent) zener diode and a 470 ohm series resistor fed by the -12 VA
output of the bias/control power supply on the bias/control board (Paragraph 4.6.1 and Figure 4-7).
4.7.1.14 Slow Run-Up Circuit - Slow run-up of the precision reference for the error amplifier is
provided by a paralleled 2.2 wF capacitor and 1 K resistor connected between pin 3 of the LM301A
error amplifier and ground. Slow run-up minimizes overshoot of regulator output voltage during
initial start-up and during recovery following a crowbar short due to an overvoltage condition.

CO ~~) ON OA B W NN

4.7.2 H7102 (+12 V) Regulator
Figure 4-10 ts a block diagram of the H7102 regulator. As seen, this regulator comprises:
Power switch
Powerswitch driver
Output filter
Overcurrent circuit
Error amplifier
Ramp generator
Pulse width modulator (PWM)
20 kHz clock

4-24

9.
10.
11.
12.
13.
14.

Turn-off-drive circuit
Flyback diode
DC OK circuit
Crowbar
Voltage reference
Slow run-up circuit.

With minor differences, the purpose and operation of these regulator sections are the same as those
described under heading of the H7101 (-5.2 V) regulator in the preceding subsection. However, for
simplicity of reference and to point out any differences between the two regulators, the functional
sections are as follows.
4.7.2.1 Power Switch — The power switch of the H7102 regulator uses a single transistor in conjunction with the pulse transformer to develop a duty-cycle-controlled pulsed-dc output in response to
the closed-loop feedbackcircuitry for correcting sensed error voltage in the +12 Vdc output. The
powerswitch is energized by the +30 V output from the 350 wh choke on the motherboard. The 1000
uF filter capacitor on the H7102 board is automatically connected across the unregulated +30 V
output from the choke whenthe board is inserted into jack J2 on the motherboard. Line protection is
provided by the 15 A fuse at the input to the power switch transistor. The input for the turn-off-drive
circuit is taken from the secondary of the pulse transformer.
4.7.2.2 Power Switch Driver - The power switch driver uses two transistors whose turn-on is controlled by the buffered output signal of the 55 timer in the PWM. Transistor bias voltages are the +12
VA from theflyback power supply on the bias/control board. The base-drive transistors are turned on
by the leading edge of the 20 kHz conduction pulse from the pulse width modulator. Also inputting to
the base drive circuit through a normally reverse-biased diode is a +12 V regulator inhibit signal from
the H7103 status and sequencecircuit (Paragraph 4.7.3.4 and Figure 4-12). When this signal is generated upon failure of the +5 VB input to the quad comparator, pulsing of the H7102 is inhibited.
4.7.2.3

Output Filter - The output filter consists of a 250 wH choke and a 1500 uF capacitor.

4.7.2.4 Overcurrent Circuit - Current limiting in the overcurrent circuit is provided by a 0.01 ohm
resistor in series with the 250 wH choke ofthe output filter. The current throughthis resistor and the
voltage acrossit is triangular in shape and rides on the average dc output current. The monitored peak
choke current is approximately 13 A peak-to-peak. The current limit for the +12 V outputis set at 12
A.
4.7.2.5 Error Amplifier - In the error amplifier, an LM031A op amp compares the sensed output
voltage with the precision reference. The resultant error amplifier output voltage is fed to the ramp
generator.
4.7.2.6 Ramp Generator - Error amplifier output is converted to a current level in the ramp generator. This error current charges a 1000 pF capacitor in the collector circuit of the ramp generator to
establish the desired voltage ramp (+5.1 V peak).
4.7.2.7 Pulse Width Modulator (PWM) - A 555 timer in the PWM provides (from its buffered output) the input signal for control of the base drive transistors in the power switch driver (Paragraph
4.7.2.2). Pulse width varies with error voltage over the range of 0 to 25 us. Figure 4-11 is a timing
diagram for the PWM. When theclock pulse goes low, the PWM timeris triggered on and the 1000 pf
capacitor connecting the clock timer and the PWM timerstarts charging. As shown in the diagram,
base drive in the PWM starts when the clock signal falls to zero and ends when the capacitor 1s charged
to 5.1 V. If the +12 V output increases above the precision reference level, the capacitor chargesat a
faster rate. Since the clock pulse is fixed (25 us on and 25 us off), base drive decreases proportionately
with the increase in +12 V output to return this voltage to normal.
4-25

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TK-0588

Figure 4-11

H7102 Regulator Timing Diagram

4.7.2.8 20kHz Clock - The clock establishes the basic operating frequency of the +12 V regulator. A
series resistor and capacitor connected to the control voltage input of an E555 timer provide for
external sync by a signal originating at the clock (BC8) of the bias/control power supply on the B/C
board (Paragraph 4.6.1.8 and Figure 4-7). When the clock pulse at the buffered output of the clock
timer goes low, the pulse width modulator is triggered on.
4.7.2.9 Turn-off-Drive Circuit - Rapid turn-off of the power switch transistor between conduction
and reset is effected by a series-connected diode, 100 ohm resistor and 0.1 wF capacitor connected
between the secondary and primary of the pulse transformer. When the power switch transistor 1s
turned on, the capacitor is charging through the resistor. When the switch is turned off for the reset
portion of the cycle, the capacitor generates a large reverse pulse on the base of the transistor to
sharpen the turn-off transition.
4.7.2.10

Flyback Diode - An 11-10715 diode between the power switch and the LC outputfilter is

reverse-biased when the power switch is turned on. When the switch turns off, the flyback diode is

forward-biased and permits energy stored in the outputfilter to flow through the load for the duration
of the reset interval.

4.7.2.11_| DC OK Circuit - The DC OK circuit consists of a transistor switch and voltage divider.
Whenthe sensed dcat the overcurrent circuit approaches +11.4 V, the collector of the transistor goes
high to generate a -5 Vdc OK output. This signal is wire ORed with the +12 Vdc OK and +5 Vdc OK
signals at the input to the regulator-fail gate (BC28) on the bias/control board (Paragraph 4.6.3.5).
Whenanyof these failure-indicator signals goes low, the resultant high from the regulator-fail gate
turns on the red Plug-In-Regulator-Failure lamp of the H7100 status display (Paragraph 3.4.3).
4-27

4.7.2.12 Crowbar - Load protection for the +12 V regulator is provided by two SCRsthat turn on
sequentially to apply a short circuit across the output when its voltage exceeds 14.1 V, maximum.
Undershort circuit conditions, (crowbarfired) H7102 output voltage falls to 0.8 V until the crowbar ts
turned off. If the main (power) switch transistor short circuits, the crowbar will turn on and the IS A
fuse at the input to the base drive circuit will blow.
NOTE
Protection against the application of an external
voltage to the output is not provided.
4.7.2.13 Voltage Reference — The precision voltage reference for the LM301A error amplifier is provided by a 1/4 M5.1AZ]1 (5.1 V, 1 percent) zener diode and a 330 ohm series resistor fed by the +12
VA output of the bias/control power supply on the bias/control board (Paragraph 4.6.1 and Figure 47).
4.7.2.14 Slow Run-Up Circuit - Slow run-up of the precision reference for the error amplifier is
provided by a transistor whosebase voltage is provided by a voltage divider with +12 V source. This
arrangement charges a 68 wF capacitorslowly between pin of the LM301A error amplifier and ground.
Slow run-up minimizes overshoot of regulator output voltage during initial start-up and during recovery from a crowbarshort.

BWN-

4.7.3 H7103 (+5 B) Regulator
The H7103 (refer to the block diagram, Figure 4-12) comprises:
A +5 VB* switching regulator
—5 VB series regulator with 3-terminal output regulator
12 V bias power supply
Status and sequencingcircuit.

Under normal power-up conditions, the H7103 receives input power from both the +30 V and floating
30 V power sources on the motherboard. Bias voltages (+12 VA and -12 VA) are supplied from the
bias/control power supply on the bias/control board. Under normal power-up conditions, the H7103
delivers +5 V at 20 A and -5 V at 0.2 A.
Under power-fail conditions, the H7103 (like the H7102) regulator receivesits input power from the 36
V battery pack of the H7112 memory battery backup power supply. Underthese conditions, the -5 VB
power output remains the same (-5 V at 0.2 A), but the +5 VB and +12 VBcapabilities are reduced to
18.5 A and 4.6 A, respectively.

pee
——b

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4.7.3.1

+5 VB Regulator - The +5 VB regulator circuit on the H7103 board consists of:
Power switch and base drive circuit
Output filter
Overcurrent circuit
Error amplifier
Ramp generator
Pulse width modulator (PWM)
20 kHz clock
Crowbar
Turn-off-drive circuit
Voltage reference
Slow run-upcircuit.

*The ‘“‘B” designation indicates battery backup for this output. Voltages with an ‘‘A” suffix originate in the
bias/control powersupply.

4-28

-—-—- — -— -— -— -—_TURN-OFFDRIVE

25 — 40 Vdc

CIRCUIT

|
i

POWER
SWITCH &
BASE
DRIVE

OUTPUT

OVERCURRENT

FILTER

CIRCUIT

+5 VB @ 20A
=<

CROWBAR

I
oe
12 Vde

PULSE

RAMP

ERROR

BIAS
SUPPLY

al
MODULATOR a

GENERATOR [*

AMPLIFIER

EXT.SYNC
———*}

|
a

STATUS &

SLOW
RUN-UP
CIRCUIT

VOLTAGE
REFERENCE

CLOCK

|
+5 VB

REGULATOR |

[

SEQUENCING
CIRCUIT

quaaD

<——

20 kHz

VOLTAGE

CONTROLLED OSC.

NEGATIVE
REGULA

~10 V + 3V

3-TERMINAL REGULATOR

-5VB @ O2A

}_—___

[

-5 VB REGULATOR

+12V REG. INHIBIT_

+12V REG. SHUTDOWN }H7102 BOARD
+5VB DC OK TO REGULATOR FAIL GATE (BC28)
-

25 — 40 Vdc

TK-0595

Figure 4-12 H7103 (+5 B) Regulator Block Diagram

4-29

Power Switch and Base Drive Circuit
The power switch and base drive circuit consists of two power-switch transistors, pulse transformer,
balun transformer and two base-drive transistors. When oneof the base drive transistors is turned off
and the other one turned on, the voltage across the secondary of the pulse transformerreverses,
causing the two power-switch transistors to turn on. The balun transformer forces these two transistors to share the current. If the base drive signal from the PWM becomes narrower(error voltage
hasdecreased), the power transistors will not remain on as long, thereby reducing the average value
and reducing the output voltage of the regulator. A flyback diode permits thefilter choke of the output
filter to continue delivery of output voltage when the power switch transistors turn off.
Output Filter
The output filter of the +5 VB regulator consists of a 25 wH choke and 15,000 wF capacitor.
Overcurrent Circuit
In the overcurrentcircuit, current limiting is provided by tworesistors in series with a 25 wH choke in
the +5 VB output circuit, an arrangement that permits monitoring of peak choke current (approximately 6 A peak-to-peak). The current through the two (paralleled) resistors and the voltage across
them is triangular in shape and rides on the average dc output current. The current limit for the +5 V
Output is set at 24 A.
Error Amplifier
In the error amplifier, an LM301A op amp comparesthe sense voltage with the precision reference
(+5.1 V) and generates an amplified error output that is converted to a current level.
Ramp Generator
The conversion of error amplifier output to a current level is accomplished by the transistor of the
ramp generator. This current charges an 8200 pF capacitor to generate the desired voltage ramp (8.0 V
peak).
Pulse Width Modulator
The 555 timer of the PWM provides the input for the base drive transistor. Pulse width varies with
error voltage over a range of 0 to 25 us. Figure 4-13 is a timing diagram for the PWM. Whenthe clock
pulse goes high, the PWM timeris triggered on and the 8200 pF capacitor starts charging. As shown in

the diagram, base drive in the PWM starts when the clock signal falls to zero and ends when the 8200

pF capacitor is charged to 8.0 V. If the +5 B output voltage increases above the precision reference
level, the capacitor charges at a faster rate. Since the clock pulse is fixed (25 us on and 25 us off), base
drive decreases proportionately with the increase in +5 B output voltage to return this voltage to
normal.
|
20 kHz Clock
The +5 B (20 kHz) clock establishes the basic operating frequency for the +5 B regulator section. A
series resistor and capacitor provide for external sync by a signal originating at the clock (BC8)of the
bias/control power supply on the B/C board. The 20 kHz operating frequency is developed by the
output of a 555 timer in the clock circuit.
Crowbar(Over-Voltage) Circuit
Load protection for the +5 B regulator is provided by two SCRsthat turn on sequentially to apply a
short circuit across the output when its voltage exceeds 6.3. Under short circuit conditions (crowbar
fired), output voltage falls to 1.5 until the crowbar is turnedoff. If the main (power) switch transistors
short circuit, the crowbar will turn on, and fuse F1 at the input to the regulator board will blow.
NOTE
Protection against the application of an external
voltage to the output is not provided.
4-30

25 us

0
“

20 kHz CLOCK

25us |

PWM-TIMER
TRIGGER

0
12V

5 —__]
=

|
1|

RAMP GENERATOR
OUTPUT

mal

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TK-0594

Figure 4-13.

PWM Timing Diagram for +5 V Switching Regulator of H7103 Board

Turn-Off Drive Circuit
Rapid turn-off of the power switch transistors between conduction and reset is effected by seriesconnected diode, 100 ohm resistor and 0.1 wF capacitor connected between the secondary and primary
of the pulse transformer. When the power switch transistor is turned on, the capacitor is charging
through the resistor. When the switch is turned off for the reset portion of the cycle, the capacitor
generates a large reverse pulse on the base of the transistors to sharpen the turn-off transition.
Voltage Reference
The 5.1 V, 1% precision voltage reference for the LM301A error amplifier is provided by a zener diode
in series with a 330 ohm resistor fed by the +12 V regulated output of the H7102 board.
Slow Run-Up Circuit
Slow run-up of the precision reference for the error amplifier is provided by a 39 wF capacitor which,
with the zener diode for precision reference, is connected between pin 3 of the LM301A op amp and
ground.
4.7.3.2 -5 VB Regulator
The -5 VB regulator section comprises:
1.
2.
3.

A voltage controlled oscillator (VCO)
Negative regulator
Three-terminal regulator.

4-31

Voltage Controlled Oscillator
The VCO determines the basic operating frequency (20 kHz + 2 kHz)of the -5 VB section. Pulse ON
time is 13 ws when the raw dc is 25 V and 6.5 us whenit is 50 V. Pulse OFF time is fixed at 39 us. These
parameters keep the energy in the associated 400 wH choke constant and the input voltage to the 3terminal regulator constant at approximately -10 V.
The negative regulator develops the -10 + 3 V required by the 3-terminal regulator across a 50 uF
capacitor connected between the input to this device and ground. For a raw dc voltage of 25 to 50 V,
the waveform at the output of the pass transistor in the -5 V regulator circuit1s:

+30 VDC

—10 VDC
<—__T———+

|<——T

OFF

ON
TK-0884

3-Terminal Regulator
The 3-terminal regulator of the -5 VB section holds the -5 V output constant within +5 percent, and
provides its own internal protection. Overcurrent for the pass transistor of the negative regulator is
provided by a 0.5 ohm current sensing resistor in series with the 400 wH choke. An overcurrent condition causes the 555 timer of the VCO to turn off until the start of a new cycle.
4.7.3.3, 12 V Bias Supply for -5 VB Regulator
The 12 V bias supply provides the start-up potential for the -5 VB regulator and the status and
sequencing circuit.
4.7.3.4 Status and Sequencing Circuit
The status and sequencing circuit uses an LM339 quad comparator to sensethe availability of -5 VB
and, indirectly, the +5 VB and +12 VB. The timing sequence for the -5 VB, +5 VB and +12 VB
regulatorsis:

0
~3V
—5 VB

iJ Jf
+5VB

s/¢

1.5 V CROWBAR LEVEL
NN
TK-0883

4-32

As shownin the block diagram of Figure 4-12, the following sequencer outputs are provided:
1.

+12 V regulator inhibit (to the power switch driver of the H7102 regulator board)

+12 V regulator shutdown (to the crowbar external input of the H7102 board)

+5 VDC OK (to the regulator-fail gate, BC28, of the bias/control board; refer to Figure 4-7
and Paragraph 4.6.3.5).

4-33

APPENDIX A
GROUNDING

The following material on DIGITAL’s current grounding practices comprises Chapter 3 (GROUNDING) of a forthcoming revision to the Digital Site Preparation Guide (EK-CORP-SP-001). Its inclusion here is for the convenience of personnel concerned with grounding asthis affects VAX system
installations.
A.l INTRODUCTION
An importantpart of site preparation is to ensure that both the power and earth reference distribution
comply with DIGITAL’s requirements. The successful installation of a computer system requires preinstallation planning and careful attention to the details of the group distribution. This need should be
approached by viewing the complete system in its physical and electrical environment. A properly
planned site should include a diagram of the physical layout and an electrical diagram of the power
and earth reference distributions.
A.2)> GROUND DEFINITION AND PURPOSES
The word ‘“‘ground” as used within an electrical connotation means ‘‘a connection to the earth for
conducting electrical current to and from the earth” (definition from IEEE No. 81). In recent years,
this definition has been expandedto include the need to establish a reference potential. There are two
purposes for establishing an earth connection to equipment and systems.
1.

Safety - to prevent a shock hazard in the event that an equipment chassis frame or housing
develops a hazardous voltage due to lightning or an accidental breakdown of wiring or

components.

Electromagnetic compatability — to reduce susceptibility interference equipment chassis are
earth referenced at one common point.

A.2.1 Safety
The ac powerdistribution is governed by local, national and international regulations which deal with
standards on wiring and otherelectrical requirements. All codes generally require the use of a safety
(grn, grn/yl) conductor for electrical equipment. The requirement, generally stated, is that each hot
(phase) and return wire (neutral) from a power source to a piece of equipment be accompanied by a
safety conductor. The size of the safety conductor should be equal to that of the hot wire. This same
requirement applies for all power systems (i.e., split-phase delta, wye, etc). Safety codes will generally
require that the safety ground conductor be connected to any conducting surface that an operator can
touch on the electrical equipment and can be energized by an electrical fault. This wire, under normal
operation, should not carry 50/60 cycle ac return current. If the hot (phase) wire of a piece of equipment were accidently shorted to the frame, the frame of the equipment would then become raised to
some hazardousvoltage. If someone were touching that frame, their body could become the current
path to earth ground. These safety shock hazards can be avoided by bonding the grn/yl safety ground
_ wire to the equipmentchassis. In this case, when a fault occurs within the equipment, the safety wire
acts as the return path providing a very low impedance connection, and causing the circuit protection
device (fuse or circuit breaker) to trip. All DIGITAL equipment having a powercordleaving a cabinet
has the green/yellow safety conductor from the ac power cord connectedto the chassis.
A-1

To help reduce line conducted electromagnetic interference, filters are often used at the powerline
entry of electronic equipment. Capacitors in these filter networks may be placed from both hot and
neutral lines to ground to decouple (shunt) radio frequency interference (RFI). As a result there is a
small leakage current in the grn/yl safety conductor. Various national and international organizations
limit the size of such capacitors by placing a limit on the resultant reactive current flowing in the grn/yl
safety wire. DIGITAL is currently limiting the reactive current to 3.5 mA per cabinet powercontroller
cord in new equipment.
Another aspect of the safety problem involves providing a low-impedance path to earth in order to
protect personnel and equipment during lightning strokes in an electrical storm. The purposeof lightning protection therefore, is to dissipate lightning energy in earth. When an ionized column oflightning strikes, it will seek out higher-elevation, sharp surfaces and low impedancepaths from earth. To
attain protection, lightning rods may be placed on the top of buildings to attract the stroke and
dissipate the energy pulse into the earth.
However, depending upon where a building is located geographically, lightning protection may or may
not be employed. In any event, building steel (vertical and horizontal beam lattice networks) is usually
grounded providing minimumlightning protection. If the steel structure is not well earthed, the stroke
current may divide betweenthe structural steel and safety wiring if attached inadvertently. This means
that a building’s steel structure and/or internal wiring becomesa naturalpath for the lightning current
pulse to follow. This is an important consideration and close attention should be paid when laying out
the power grounddistribution of the computer system. Figure A-1 depicts the potential problem that
can occur if a system is inadvertantly “‘grounded” to a building frame. This is also in contradiction
with the single-point ground scheme that will be explained in Paragraph A.4.2.
LIGHTNING
STROKE

LIGHTNING STROKE
CURRENT PULSE

<—- EARTHQUAKE VIBRATION
DAMPERS MAYBE INSTALLED
(1F SO - SHOULD BE SHUNTED
BY GND STRAPS)

SERVICE
ENTRANCE

TK-0842

Figure A-1

Lightning Stroke Current Path (Shown with System Grounded to Building Steel)

A-2

A.2.2 Electromagnetic Compatibility
To accomplish interference compatibility through an effective grounding system, both system electrical components and cabinet frames should be maintained at the same reference potential. This is
accomplished by providing a single, commonreference point for each system cabinet and each subsystem logic reference in the system.
The purpose of this schemeis to make the system less susceptible to the flow of RF (radio frequency)
currents including static discharge. Any two points on a cabinet or system of cabinets may develop a
potential difference at some frequency; it is therefore essential to provide a low impedancepath to
shunt interference current back to ground, thus circumventing the susceptable areas of the system.
Static discharge, whether radiated from a nearby point or conducted directly onto the cabinets them-

selves, is a prime sourceof interference currents. Other sourcesof interference currents are flourescent

lamp noise, harmonics from ac power mains, and line conducted impulses from machinery.

Virtually all electrical equipment maycreate noise on powerlines when operating; computer systems
are no exception. To mitigate this type of interference, filters are placed at the powerline entry of
computers. In this way, RF noise generated from nearby sources, can be shunted to earth ground.

A.33

SAFETY GROUND CONSIDERATIONS

The ultimate goal of any equipment groundingis to ensure personnel safety.
To be effective, safety connections must provide a low-impedancepath at power frequenciesto earth.
An ideal ground reference would be a zero-potential, zero-impedance system that could be used as a
reference for both powerand signal reference. This would allow all undesirable signals and ambient
radiation to be diverted to it. Ideally, it should be able to absorball signals and radiation while
remaining stable. This is the foundation for obtaining reliable, interference-free equipment operation
and all of the inherent shielding qualities of the cabinetry.
Becauseof its multiple function — safety being the most important -— all safety ground circuits must be
carefully treated. The system’s safety ground must be routed with the ac power conductorsbackto the
powersystem transformer. The safety conductor may be insulated from conduit and other connections
back to this point. The powertransformer reference point must then be terminated at a low resistance
earth connection.
In its path from the DIGITAL cabinets to the transformer earth reference the grounding conductor
should not connectto:
e The ac neutral — this connection should be madeonly at the transformer or service entrance
e Grounds from equipment whichis not part of the computer system
e Metal structural grounds, building steel, water pipes,etc.
A.3.1 Earth Ground Reference
This section discusses the techniquesin establishing earth grounding reference systems that are compatible with requirements of variousstructure types.
This simplest and somewhat misleading idea of a good “‘ground”’ for an electrical system is a section of
iron pipe driven into the earth with a wire conductor connected from the pipes, and pipelines historically have been an excellent media for connecting structural steel and powerdistribution systems to
earth. This has been due to the large amountof surface area exposed to the earth and relatively large
depths to prevent freezing when suchpipingis buried. It has been standard practice for manyyearsto
bond metallic structures above ground to water and gas pipes by means of copper bonds or copper
ground rods. Unfortuantely, copper in its various forms creates an undesirable coupling of dissimilar
metals. When in contact with iron orsteel, copper will act as a cathode to accelerate corrosion, thereby
increasing the bond inpedancein time. Due to both the resultant corrosion and economics of under-

A-3

ground piping systems, utility companies are leaning toward coated pipes or non-conductive pipes and
couplings which will eliminate this widely used method of grounding. This may, therefore, be an
unsuitable path for electrical current to flow (if a fault occurs) to protect personnel and equipment.
Thus to establish an effective, noise free ground (earth reference) it may be necessary to install dedicated grounding systems for all large computerinstallations. Resulting from the need for dedicated
grounding systems, it becomes necessary to utilize ground stakes and meshes.
A.3.1.1 Earth Ground Stake(s) - A practical earth electrode that provides a low ground resistanceis
not always easy to obtain. Earth resistivity has an important bearing on resistance, as does depth,
electrode size and earth salt content. It is beyond the scope of this guide to go into great detail about
any of these parameters. It is mentioned, however, to give insight into the necessary considerations.
Current in a grounding system is primarily determined bythe leakage current during normal operation
of the electrical equipment. This current should, for safety reasons, be limited and is governed under
various national and international standards. The effectiveness of a safety ground system (Figure A-2)
is determined byits ability to shunt fault current to ground. To accomplish this, the resistance of the
grounding system must be very small. Three componentsthat constitute the resistance of the grounding systems are:
:
1.
2.
3.

Resistance of the conductor connecting to the ground stake.
Contact resistance between the ground stake andthe soil.
Resistance of the body of earth immediately surrounding the ground stake.

A.3.1.2 Earth Ground Grid Meshes - Ground-grid meshes are often required to complementrods or
can be used seperately when deep-driven rods are impractical due to soil and terrain considerations.
Groundingresistance can be reducedsignificantly below that of the earth stake by buried grid meshes.
Increasing the numberof grids and/orthe area of grid coverage can alsosignificantly lower the ground
resistance.
Ground rod and grid-mesh criteria developed in these sections can berealized for effective implementation in extremely rocky or frozen soil, when deep penetration of ground rodsis impractical. In such
cases ground grids may be used. However,in regions subjected to extreme climatic variations, earth
resistivity will vary considerably causing resistance changesin shallow buried grid meshes. In various
localities with dry soils, earth resistivity may be extremely high regardless of the depth of the ground
rod penetration. In situations such as these, other techniques may be utilized to obtain necessary
lowground resistance: impregnation of soil with salt solution, immersion of grid or plate in nearby
water sources.

A.4

GROUNDING REQUIREMENTS

To keep electrical noise under control and preserve system integrity, the safety ground system described in the following paragraphs is recommended. Other schemes may also provide adequate
grounding; however, any alternate system should be carefully studied to ensure that compatible
grounding is provided.
A.4.1 Primary Power Distribution
The primary power feeder for the entire system (including all external components such as terminals,
other systems in direct communication, laboratory data collection equipment, etc.) should be unique
to the system. All power, therefore, for all system related components should be derived from the same
system distribution panel. In some cases, however, this may not be possible. Various reasons for not

using a unique system powerfeeder include:
e

The new computer system required more power than one feeder could deliver.

The new computer system communicates with another existing system which does not have
enough reserve power to power the new system, or the power is incompatible (voltage/frequency).

A-4

BRAZED CONNECTION
PREFERED
GROUNDING
ELECTRODE

RESISTANCE OF
SURROUNDING
EARTH

CONTACT
RESISTANCE

I
CURRENT

\\ \
MAAN YS

TK-0485

Figure A-2. Earth Ground Stake
(Ground Rod)

The new computer system is distributed over a very large area such that branching from a
single distribution panel is impractical.

In any of these cases, it must be assured that both powerdistributions are referenced together and that
each powerreference point is at the same potential.
A.4.2 Power Reference Distribution
Since there is a need to reference individual subsystems to powerline ground for safety reasons,all
DIGITAL computer cabinets containing a subsystem contain a powercontroller (861, 866, 869,etc.).
The powercontroller is the power distribution for all subsystems within a cabinet andis not designed
to power external devices. The ac power cord for the power controller contains a separate insulated
grn/yl conductor for the safety ground and the connection to the equipmentchassis is made within the
controller. This conductor must then be connected to the system earth reference. All electrical outlets
providing power for a system, shall have a safety wire, (grn/yl), connected between the receptable
_ ground connection and the system earth reference within the distribution panel. These wires should be
isolated from all other connections (including building steel). When power wiring is run in either

A-5

conduit or armored cable (Bx) betweenthe receptable and powerdistribution panel, it may be necessary to install Isolated Ground Receptacles. These receptacles are designed to isolate the safety conductor (grn/yl wire) from the metallic box. This will then effectively isolate the system safety ground
from external noise sources (fault currents) back to the system earth reference. The system earth
reference will then be connected to the safety earth ground at one point (refer to Figure A-3, Ground
Reference Distribution).
For small data processing systems requiring only one receptacle, the system earth reference can be
identified as the connection within the receptacle. For larger systems requiring a customer power
distribution panel, the system earth reference will be identified as the junction whereall of the grn/yl
safety wires are common within the panel.
A.4.2.1 Testing the System Earth Reference —- A convenient means should be providedto verify that
the entire system is indeed referenced to earth at one and only one point (the system earth reference
point). It is necessary that this point be will defined, and labeled. It should additionally have a means
of disconnection (single stud/lug) whereby this reference can be lifted and the system tested to determine if there is any point other than this point at which the system is referenced to earth.
Twotests can be performed which will verify the proper isolation of the system reference point. These

tests should only be performed with the assistance of an electrician.
1.

With power applied to the system, measure the current in the system earth return wire. This
measurement should be made with a device which can measure current without disconnection of the wire (a clamp-on ammeter). The maximum current in the system earth
return should not exceed 3.5 mA (for new equipment) for every power cord exciting a cabinet in the system. Current in excess of this amount indicates improper primary
power/reference distribution, and should be investigated before continuing.

Removeall primary powerto the system. This may be accomplished by either:
e
e

Opening dedicated system circuit breakers at the customer’s powerdistribution panel.
For smaller systems not requiring a dedicated power panel, unplugging the ac power

cord is sufficient.

Disconnect the system earth return from the safety earth ground bus (Figure A-3). There should bea
minimum of 100 ohms resistance between the system earth reference and the safety earth ground bus
measuredat dc.
WARNING
‘When the system earth reference is removed from the
primary or dedicated safety earth ground bus, there
may exist hazardous voltages between the system
earth return wire and the safety earth ground bus.
This wire should thus be handled accordingly. Before
any resistance measurements are made that require
the disconnection of this return wire, the voltage between the system earth return wire and the safety
earth ground bus should be measured to determineif
a hazardous condition exists.

A-6

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A-7

A.4.3 Inter-Cabinet Connections
Each cabinet of the system is provided with ground lug terminals. Upon installation, cabinets that are
bolted together also should be electrically bonded with a ground braid strap or stranded copper (#10
AWG) conductor. Systems that are configured with standalone cabinets or separate groups of cabinets
must also maintain chassis ground for signal integrity. In this case, the ground lugs should be connected via a #4 AWG (5 mm, 0.20 inch) insulated copper wire or standard #4 AWGinsulated welding
cable of the same size. This signal integrity reference cable (SIRC) should be asshortas possible and
dressed along the data cable path.
All free-standing mass-storage devices must also be referenced to the system unless metallic troughs
are used which connect cabinet chassis together. For this reason, the SIRC must be installed. This
cable should also be routed close between 15-50 cm (6-20 inches) to the data cable to reduce ground
loop area, and connected to the cabinet containing the drive controller. A Burndy QA4C-B solderless
lug (or equivalent) may be used for termination.
A.4.4 Raised Floors
A raised floor is generally a desirable feature. For safety purposes, the floor grid, being either separate
pedestals or pedestals with rail construction should be grounded. This can best be achieved by connecting the floor grid to the safety earth ground busin the distribution panel. It must be understood
that when it is attached to this point, it must be isolated from buildingsteel, electrical conduit, airconditioning duct, etc. If this is not accomplished, sneak paths for external currents and EMI may
contaminate the system reference.
A.4.5 Customer Convenience Outlets or Devices
It is recommended that any customer convenience devices, e.g., coffee pots, vacuum cleaners, electric
typewriters, etc., receive their power from a branchcircuit independent from that powering the system.
This branch circuit may be taken from the same primary powersource as the system without adverse
effects. The intent is to ensure that the system earth return does not carry earth return currents from
the customer convenience devices.

A-8

APPENDIX B
H7100 POWER SUPPLY AND REGULATOR REPLACEMENT

Replacement of the H7100 dc power supply or reconfiguration of its regulator complement can be
accomplishedin the field with the following parts from the VAX-11/780 CD kit:
l.

One configurable H7100 dc power supply (includes the bias/control board and provides
+5.1 V output)

One 5412560 H7101 -5.2 V regulator board

One 5412556/5412558 H7102/H7103 +12 V/+-5 VB regulator board.

Corrective maintenance guidelines for the H7100 are:
Regulator Failure
If the 5412560, 5412556 or 5412558 fail, replace the failed board with board from the CD kit.
Basic H7100 Failure
If the basic H7100 fails, replace it with the H7100 from the CD kit.
H7100 Fails, But Its Regulators are Good
If the basic H7100 fails, but its regulators arestill good:
1.

Remove regulators from failed H7100.

Insert the removed regulators in the H7100 of the CD Kit.

Removethe blank jack J6/J7 from the new supply.
Use cables from the failed supply to connect up regulators (Figure B-1); install J6 or J7 in
rear panel cutout.
Use insulator boards from failed supply.
Attach appropriate decals at rear of supply to show regulator configuration (Figures 3-31
and 3-32).
Decal 3614762-00 - H7100 Power Supply with H7101 Regulator Board.
Decal 3614762-01 - H7100 Power Supply with H7102 and H7103 Battery Backup and Regulator Board.

B-1

H7100
REAR

J Panel
H7101

-1°9

(-5.2 V)

12-WIRE OUTPUT CABLE 7014545-0-0)

SEE PLH7101-0-:0&ICH7101-01

7-WIRE

INPUT CABLE 7014548-0-0

)

H7102

los

(+12VB)

Pel2 7103?
(+5VB)

| 46

H7100

4-WIRE OUTPUT HARNESS 7014546-0-0
SEE:

PL H7102-0-0
PL H7103-0-0
IC H7103-0-1

REAR

7 panel
15-PIN
J7

11-WIRE OUTPUT HARNESS 7014546-0-0

\ H7100

MIDDLE PANEL

I 46pin

9-PIN J2 (BATTERY ADAPTOR)
H7100 FRONT PANEL
4-WIRE CABLE FROM H7112 B.B.U. PS.

/
NOTE:
'‘
REFER TO H7100 INTERCONNECTION DIAGRAM H7100-0-3

Figure B-1

TK-0434

Basic H7100 DC Power Supply, Regulator Boards, Cables and Harness for Corrective
Maintenance on Failed DC Supply

If replacement cable or harness are needed, order separately (they do not come with kit):
7014545-0-0 — Output cable, 12-wire for H7101 board

7014546-0-0 - Output harness, 4-wire/12-wire for H7102/H7103 boards
7014548-0-0 - Input cable, 7-wire, for H7103 board
1700021-04 - Insulator board (electromagnetic shield).

B-2

VAX-11/780 POWER SYSTEM
TECHNICAL DESCRIPTION
EK-PS780-TD-001

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