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EK-0TU78-PS-2

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Document:	TU78 Subsystem Pocket Service Guide
Order Number:	EK-0TU78-PS
Revision:	2
Pages:	120
Original Filename:

OCR Text

EK-0TU78-PS-002

Prepared by Educational Services
of

Digital Equipment Corporation

1st Edition, May 1981
2nd Edition, March 1984

The material in this manual is for informational purposes and is

subject to change without notice.
Digital Equipment Corporation assumes no responsibility for any
errors that may appear in this manual.

Printed in U.S.A.

NOTICE:

This equipment generates, uses, and may emit radio frequency

energy. The equipment has been type tested and found to comply
with the limits for a Class A computing device pursuant to Sub-

part J of Part 15 of FCC Rules, which are designed to provide

reasonable protection against such radio frequency interference.
Operation of this equipment in.a residential area may cause interferencein which case the user at his own expense may be. required
to take whatever measures may be requ1red to correct the
interference.
“

The following are trademarks of Digital Equipment Corporatlon

Maynard, Massachusetts

DECUS
DIGITAL

dlifa]i]t|a]1

DECsystem-10
. MASSBUS
DECSYSTEM-20
PDT

DECwriter

"RSTS-

PDP

DIBOL

RSX

UNIBUS

EduSystem

VMS

VAX

OMNIBUS

OS/8

CONTENTS
INTRODUCTION
General. . .

Operator Controls and Indicators.

. . . .

. .
TM78 Controls and Indicators. . . ..
TU78 Controls and Indicators . . . . .

O
=

Maintenance Controls and Indicators

Tools .. ..

-------------------

Spares Kit Lists . . ... ...........
TM78 SparesKit . ... .........
TU78 SparesKit . . . ...........

Recommended Spares Levels (RSL) . . .

.10

. ..
Additional TM78 RSL Parts . ..
Additional TU78 RSL Parts . ... ..

Related Documents . . . ... .. ... ...
System Diagnostics . . ... .........

TROUBLESHOOTING

B
R —

-------------------

Subsystem Overview ... ..........
TM78 Assemblies .. .............
TU78 Assemblies . .. ... .........

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2.6

Introduction
On-Line Diagnostics

------------------

.. ...........
In-Line Diagnostics . .. ... ........
Error Logs .

-------------------

Status Indicators for Troubleshooting . .
Error Codes

-------------------

2.7.1

Keypad Function Summary

2.7.2

Errors . .

2.7.3

Parameters

2.7.4

Maintenance Instructions . .. ...
..

2.7.5
2.8

.. ... ... ... .....

Sample Maintenance Routine
Test Points

......

-------------------

. .. ..

-------------------

iv.

CONTENTS

CHECKS AND ADJUSTMENTS

3.1

Parts Replacement

3.2

. ... ..........
Quick Reference Adjustment

3.3

Specification . . ... ... .......
...
Write Current Adjustments . . . . ... ..

APPENDIX A

SUBSYSTEM MASSBUS
REGISTERS

APPENDIX B

EXTENDED SENSE BYTES

FIGURES
1-1

1-2
1-3
1-4

1-5
1-6

1-7

1-8
1-9

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

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

A-4
A-5
A-6

A-7

A-8
A-9
A-10
A-11
A-12
A-13

A-14
A-15

A-16

Dual-Ported TU78 Subsystem .. ...
.
TM78 Front View . . . .. ....
....
..
TM78 Module Layout (Back View)
Showing Maintenance Indicators . . . . .
TU78 Assemblies (Front View) .. .. ..

TU78 Assemblies (Back View)
TU78 Card Cage Showing

... ...

Maintenance Controls and Indicators . .
TU78 Operator Control Panel . . . . . ..
H7422 Power Supply Showing
Maintenance Indicators and Controls . .

Door Safety Interlock Switch . ... ...
TM78 Maintenance Panel . . .. ... ...
Sample Write/Read Routine .. ... ...

GCR/PE Preamp 1 PCBA Test Points . .
Interconnect F1 PCBA .. .........

Vacuum Valve and Pressure Valve . . . .
Write Head Current Waveform . . . . . . .
RH20 and RH780 Addresses. .......
Control and Status Register .. ... ...
Data Transfer Interrupt Register . . . . .
Tape Control Register . ... ........
Drive Type Register .. ... ........
Tape Unit Status Register. ... ... ...
Motion Interrupt Code Register . . . . . .

Motion Command Register . . ...
.. ..
Hardware Control Register . . ...
. ...
Configuration/Status Register . . .. ...
Control Register . . . ... ... .......
Status Register . . . ... ... ........
Virtual Address Register . .........

Byte Counter Register . . . ... ... ...
Diagnostic Register . . .. ... ...... .
Map Register . .. ...............

CONTENTS

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

B-5

B-6
B-7
B-8
B-9
B-10
B-11
B-12

B-13
B-14

Read Path Status Byte . . ... ... ....
Read Microcontroller Command Byte . . 100

Parity Read Channel Status Byte . . . .. 101
ECC Status Byte . . . .. ... ........ 102
Channel (N) Track in Error Byte ... .. 103

TU Port Status Byte . ... ......... 104

CAS Port (N) Status Byte . . .. ... ... 105
MASSBUS C Bus Status Byte . . ...
. 105
MASSBUS D Bus Status Byte ... .... 106
Write Microcontroller Error Byte . . . .. 106
Interrupt Status Byte . ... ........ 107
TU78 Status Byte . . . ... ... ...... 107
MIA Status
AByte . .. ... ........ 109
MIA Status

BByte

. ... .......... 109

B-16

MIA TU Diagnostics Byte . . . .. ...
.. 110
Retry Control Byte . . . ... .. ... ... 110

B-17
B-18

TU Software Status . . . .. ......... 111
Transfer Control Byte . .. ... ...... 111

B-15

TU78 Subsystem Detailed
Block Diagram .. ............... 112

. 113
113

Write Path Troubleshooting Diagram

Read Path Troubleshooting Diagram
TABLES
1-1
1-2

TU78 Controls . . ... ... ... ......
TU78 Indicators . . . ... .. ........

1-3

TU78 Maintenance Controls . ...
.. ..

2-1

TM78/TU78 Diagnostics

2-2

In-Line Self-Test Microdiagnostics . .

. ... ......

2-3

Troubleshooting Indicator Functions

2-4

Interrupt Code to Failure Code . . .. ..

. .

2-5

Keypad Error/Status Codes

2-6

ParameterItems . .. .. ...........

2-7

Maintenance Instruction Codes

3-1

Checks/Adjustments When Replacing
Parts

... ... ..
. . . . ..

. .. ... ... .

3-2

Adjustment Specifications

3-3

Vacuum and Pressure Valve

. ... ... ..

..................

A-1

Data Transfer Function Codes . . . . . ..

A-2

Nondata Transfer Function Codes

B-1

Read Microcontroller Status Codes

Components

B-2

. . .

89
99

Read Microcontroller Command

Codes

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101

INTRODUCTION

1.1

GENERAL

This document is designed for use by a person trained
to service a TU78 subsystem. A TU78 subsystem is
made up of a MASSBUS controller (RHXX), a TM78
formatter, and a TU78 tape transport. Procedures are
short, and support a maintenance philosophy of module
replacement.

This chapter presents an overview of the formatter and
transport for quick review. Chapter 2 is troubleshooting
information. Use of error logs, diagnostics, and maintenance panel features allow rapid location of malfunctions. Chapter 3 lists all adjustments in quick reference
format.

Programming information is not provided but register
summaries for each hardware family type are found in
Appendix A. Appendix B lists the extended sense registers available in the diagnostic and error log printouts.
1.2

SUBSYSTEM OVERVIEW

The TU78 subsystem is shown in Figure 1-1. The example shown is a dual-ported TM78 formatter, controlling four TU78 transports. A detailed block diagram
of the subsystem may be found on the foldout at the end
of this book.

1.3

TM78 ASSEMBLIES

Major TM78 assemblies are shown in Figures 1-2 and
1-3.

1.4 TU78 ASSEMBLIES
Major TU78 assemblies are shown in Figures 1-4, 1-5,
and 1-6.
1.5

OPERATOR CONTROLS AND INDICATORS

All operator controls and indicators are on the TU78

control panel. Figure 1-7 shows the panel, Table 1-1 lists
the controls and their functions, and Table 1-2 lists the
indicators and their functions.

INTRODUCTION

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INTRODUCTION

ON/OFF LINE

MASSBUS PORT A

ADDRESS

SELECT

ON/OFF LINE

MASSBUS PORT B

DRIVE

ADDRESS
SELECT

Al
A2

MASTER

DRIVE SELECT/

RESET
PUSHBUTTON

ON-OFF
LINE SWITCHES

LOGIC BACKPLANE

MASSBUS

CONNECTORS

Z :
<=5+

TU BUS

CONNECTORS

(8)
MA-7554A

Figure 1-2

TM78 Front View

INTRODUCTION

TU PORT 2

CHANNEL & 7+

STATUS

( (TRACKZ) FATAL

PARITY

CHANNEL &

ERROR

(TRACK §) FATAL

\
38

& S
CHANNEL

15N4

COLUMNS

13
12

—
(TRACK §) FATAL
CHANNEL
4

(TRACK 9) FATAL ] /
CHANNEL 3
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M8952
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ECC PROGRAM ROM
PARITY ERROR

TU PORT 3
STATUS

PARITY
ERROR
MA 61748B

Figure 1-3

TM78 Module Layout (Back View) Showing
Maintenance Indicators (Sheet 1 of 2)

INTRODUCTION

O
TU PORT
STATUS

TRANSLATOR

ERROR

PARITY ERROR

PROGRAM ROM (6)

PARITY

/ COLUMNS

5/4

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MASSBUS A"’
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/ WRITE PARITY ERROR

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TU PORT 1

MICROCOMPUTER

STATUS

PROGRAM ROM

PARITY

PARITY ERROR

ERROR

Figure 1-3

MASSBUS ““B”

~ CONTROL BUS
WRITE PARITY ERROR

e
MA 6174C

TM78 Module Layout (Back View) Showing
Maintenance Indicators (Sheet 2 of 2)

INTRODUCTION

TU78
BASE ASSEMBLY

TM78 TAPE

" FORMATTER

POWER CONTROLLER | |

(874-E SHOWN)

TU78
\

POWER

PACK
ASSEMBLY

MA.6155A
SHR-0013-84

Figure 1-4

TU78 Assemblies (Front View)

INTRODUCTION

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MA-7013
SHR-0114-84

Figure 1-5

TU78 Assemblies (Back View)

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INTRODUCTION

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INTRODUCTION

Table 1-1

TU78 Controls

Control

Function

Port
Select

It selects the MASSBUS 1/0 port(s)
allowed to send commands to this

Switch

tape transport.

Switch

Position

Function

Transport connected to
MASSBUS port A

Transport connected to
MASSBUS port B

Transport connected to both
MASSBUS ports A and B

Transport disconnected from
both MASSBUS ports and
placed in maintenance mode
(available to TM78 formatter
maintenance panel)

LOAD/

It starts one of three sequences

REW

With no tape in path, it initiates a
load sequence.

With tape in path but not tensioned,
it starts a midreel load sequence.
In a midreel load sequence the
tape loads and runs in reverse
direction to BOT.

3. With tape in path and tensioned, and
the transport off-line, the tape
rewinds to BOT. If the tape is at
BOT or if the transport is on-line,
no action occurs.

ON LINE

It switches the transport off-line or
on-line.

UNLOAD

If the TU78 is off-line, it causes the

tape to rewind and unload. If the tape

is at BOT, it unloads. If the TU78 1s
on-line, button has no effect.
RESET

Terminates all functions and clears a
load fault.

INTRODUCTION

Table 1-2

TU78 Indicators

Indicator

Meaning

Power

DC and secondary ac power are present.

BOT

Tape is at BOT.

On Line

TU78 is on-line. The transport returns
to the off-line mode if any of the
following occur.

1. ON LINE button is pressed.

2. External rewind unload command
is received.

3. Vacuum column interlock is broken.
4.

AC power is lost.

RESET button is pressed.

Front door opens.

File

Tape reel without a write enable ring has

Protect

been loaded on the transport.

Load

Load fault has occurred.

Fault

1. Autoload sequence has failed to load a
tape from a 267 mm (10.5 in) reel
after two tries.

Load sequence has failed to load tape
froma 216 mmor 178 mm (8.5 in or
7 in) reels.

1600

Tape transport is set to read or write at

6250

Tape transport is set to read or write at

1.6

1600 bits/in (PE mode).

6250 bits/in (GCR mode).

MAINTENANCE CONTROLS AND
INDICATORS

Maintenance controls and indicators may be found on
the TM78 logic gate (front and back), the TM78 power
supply (H7422), the TU78 logic cage, and the {ront of
the TU78 base assembly.

INTRODUCTION

1.6.1

TM78 Controls and Indicators

Figure 1-2 shows the front of the TM78 logic gate and

details the maintenance controls. The maintenance panel
is described in Chapter 2. To the right of the maintenance panel is a DIP switch matrix. The DIP switches

select the MASSBUS drive address for both ports and

sets either or both ports on or off-line. A dual port TM78
is considered off-line for maintenance purposes only
when both ports are placed off-line.
Figure 1-3 shows the back of the logic gate and details
some of the maintenance indicators that may be used for
troubleshooting. Table 2-3 lists the indicators and describes their functions.

Figure 1-8 shows the front of the H7422 power supply
and details the maintenance indicators and adjustments.
1.6.2

TU78 Controls and Indicators
Figure 1-9 shows a detail of the base assembly and
points out the door safety interlock switch. This switch
must be defeated to perform certain maintenance adjust-

ments. To defeat the switch pull its actuator arm down
and out with a spring hook.
The rest of the TU78 maintenance controls and in-

dicators are on PCBAs in the card cage assembly (Figure
1-6). Table 1-3 lists the TU78 maintenance controls and
Table 2-3 lists the indicators.
1.7

TOOLS

In addition to the standard DIGITAL tool kit, the following tools are needed to service the TM78/TU7S.
Included

DEC

Part
Number

Spares
Kit

—

Digital voltmeter

—

Two multilayer

W300

Reel motor

29-23206

Yes

Description
Dual trace

oscilloscope with
two X10/X1 probes

dual-height module
extenders

centering tool

Tav

LvPLH

OLY[H

Lv LH

—

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INTRODUCTION

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INTRODUCTION

DOOR
INTERLOCK

0 ¢do’oo

Figure 1-9

Door Safety Interlock Switch

Included

DEC

Part

Spares

Description

Number

Kit

Reel flange

29-23207

Yes

PCBA extender

29-23218

Yes

Lower restraint

29-23228

Yes

29-11650

Yes

29-11636

Yes

locating bar

tube fitting

Differential
pressure gauge

(0—40 inch H,0)
Differential
pressure gauge

(0-5 PSI)

INTRODUCTION

Included

DEC

Part

Description

Spares

Number

Kit

Portable accessory

29-11647

Yes

29-11635

Yes

Tape crimper

47-00038

Yes

Xcelite handle

29-10562

7 inch extension

29-11625

Yes

5/32 inch X 4 inch
Ballpoint hex driver

29-11630

Yes

Master skew tape
(1200 ft)

29-19224

Magna—See tape

29-16871

package for gauges

(2 needed)
Tachometer (decimal

readout)

developer
50X microscope with

29-20273

graticule

Heat sink compound

90-08268

Inspection mirror
(dental type)

29-19663

Cleaning kit

TUCO1

(comes
with

TU78)

Standard output
tape

29-11691

INTRODUCTION

Table 1-3

TU78 Maintenance Controls

Control

Location

Motion 1

MIA PCBA

Read/
Write

MIA PCBA

Purpose

It moves transport forward or
reverse when on-line and in
manual mode.

It selects read or write mode
when on-line and in manual
mode.

Density

MIA PCBA

Auto/Man

MIA PCBA

It selects 1600 or 6250 BPI

density when on-line and in
manual mode.

It selects auto (transport
connected to formatter) or
test mode. When in test (or
manual) mode, transport must
be on-line for other MIA
switches to function.

Data
Pattern

MIA PCBA

AGC
Exerciser

Read
PCBA

Motion 2

Control

manual mode.

Select

Reel
Servo
Disable

1.8

It selects a repeating 8-frame
pattern when on-line and in

It allows Read PCBA to lock
AGC to the ARA burst, or to
run free.

M2 PCBA

- Reel
Servo

PCBA

It moves transport forward

or reverse, on or off-line.

It disables the reel servo
amplifiers so that certain
adjustments can be made.

SPARES KIT LISTS

1.8.1 TMT78 Spares Kit (A2-W0342-10)
The following lists the contents of the TM78 Spares
Kit.

DEC
Part

Number

Description

M&950

Read data sync module

M8951

M8952

ECC module

CRC/ACRC module

INTRODUCTION

DEC
Part

Number

Description

M8953

Read path microcontroller

MZ8955

TU port module

module

M8956

M8957

M8958
M8&959

MASSBUS data interface module
Common address space module
Write translator module
Write micro/byte assembly
module

M8&960

54-14174
H7476

H7490

H7441

54-14192

Microcomputer module
Maintenance keypad/display
Power supply regulator =15.0V
Power supply regulator —5.0V
Power supply regulator 4-5.0V
AC/DC low board

1.8.2 TU78 Spares Kit (A2-W0341-10)
The following lists the contents of the TU78 Spares
Kit.

DEC
Part

Number

Description

29-23766

GCR/PE preamp | PCBA
Interconnect F1 PCBA

29-23770
29-23769
29-23763

29-23762
29-23764
29-23765
29-23231

29-23218

MIA PCBA
WRITE PCBA
READ PCBA
Control M2 PCBA

Capstan/regulator PCBA
Reel servo PCBA
Extender PCBA

29-23996
29-23989

Compressor belt, 50/60 Hz
Blower belt, 50 Hz, Lo

29-23991

Altitude
Blower belt, 60 Hz, Lo

29-23220

29-23259

Altitude
Muffler
Air filter

70-17382-15

15 ft TU bus cable

29-10562

Handle
7 inch extension

29-11625
29-11630
29-11001

5/32 inch ball-end allen driver
Phillips screwdriver blade

29-11635

Tachometer

INTRODUCTION

DEC

Part

Number

Description

29-11636

Gauge, 0-5 PSI

29-11650

Gauge, 0—40 inch H,O

29-11647

Accessory kit for gauges (2)

29-23206

Centering tool

29-23207

Locating bar

29-23228

Tube fitting

1.9

RECOMMENDED SPARES LEVELS (RSL)

In addition to the spares kit contents, the following
parts are recommended to repair 98 percent of all possible failures.
1.9.1

Additional TM78 RSL Parts

The following are additional RSL parts for the TM78.
DEC
Part

Number

Description

BC06S-25

25 ft MASSBUS cable

12-10930-01

230 Vac fan

12-11079-00

Pushbutton switch

12-11164-04

DIP switch

70-17381-0D

Flat cable

70-17400-00

Backplane

1.9.2

Additional TU78 RSL Parts

The following are additional RSL parts for the TU78.
DEC

Part

Number

Description

12-17916-02
29-16280-00
29-23216-00
29-23217-00
29-23236-00

Fan, tube axial 230V
Switch, MICRO
Sense assy, reel
Sense assy, pack
Motor assy, reel

29-23238-00

Switch, pressure

29-23239-00
29-23242-00

Switch, pressure
EOT/BOT assy

29-23243-00

TIP assy
Transducer assy, vacuum

29-23246-00

INTRODUCTION
DEC
Part

Number

Description

29-23247-00
29-23248-00
29-23249-00
29-23250-00

Circuit breaker

29-23251-00

29-23252-00
29-23257-00
29-23280-00
29-23287-00
29-23297-00

Valve assy, vacuum
Valve assy, pressure

Bearing, air
Bearing, air
Bearing, air
Compressor

Motor, gear drv
Motor, ac

Switch, backwrap defeat

29-24013

Blower assy (Below SN
SP002386)
Blower assy (SN SP002386

29-23308-00
29-23321-0P
29-23322-00

Thread block 2

29-23298-00

29-23323-00

29-23324-00
29-23325-00

29-23326-00
29-23475-00

and above)
Relay reed SS 12 Vdc

Cable, flat ribbon (AMTIE)

Thread block 4
Thread block assy
Thread block assy
Thread block assy
Hub reel

Head, R/W

29-23767-00
29-23768-00
29-23771-00

Motor assy, capstan
Controls assy

10-11643-00
12-14405-00

Door, tape transport,

18,000 MFD 25V +75-10%

front

29-23208-00
29-23209-00
29-23211-00
29-23215-00
29-23219-00

Hub, machined
Flange, front

Interconnect D1
Door assy, buffer box
Spring, compression

29-23222-00

Spring, bellville

29-23223-00

Washer

29-23241-00

Cleaner, tape
Guide plate “R”

29-23255-00

29-23256-00

Guide plate “C”

INTRODUCTION

DEC
Part

Number

Description

29-23258-00

Transformer

29-23279-00

Filter, RFI

29-23283-00

Guide, Air

29-23284-00

Hub, motor 50 Hz

29-23285-00

Hub, motor 60 Hz

29-23286-00

Catch, spring

29-23288-00

Receptacle, fastener

29-23309-00

47000 MFD 15 W VDC+ 75%-10%

29-23310-00

61000 MFD 50 W

29-23311-00

RECT, BRDG 25 A 100 PN

29-23312-00

RECT, BRDG 10 A 100 A

VDC+100%-10%

29-23320-00

33020 W 10% WW

29-23361-00

Cap plug

29-23655-00

Kit, vac hose/tubing

70-17143-00

Fan assembly TU78

90-07221-00

Fuse, reg blow, 5 A, 250V

90-08835-00

Fuse, reg blow, 20 A, 32V

90-08838-00

Fuse, reg blow, 10 A, 32V

29-11691-00

Tape MSTR OTPT 1200X1/2

29-16871-00

Magnasee

29-19224-00

Tape, master skew 1200

29-20273-00

Microscope 50 X

47-00038

Tape crimper

90-08268

Thermal compound

INTRODUCTION

1.10 RELATED DOCUMENTS
The following list describes documents related to the
TU78 subsystem.

Document
Title

Number

TM78

EK-0TM78-UG

Magnetic

Contents
Description,

programming,

Tape

and

Formatter

installation

User’s

information of

Guide

the TM78

TM78

EK-0TM78-TM

Theory of

Magnetic

operation,

Tape

programming

Formatter

information,

Technical
Manual

installation,
and maintenance
of the TM78

Formatter and
H7422 Power

Supply
TU78

EK-0TU78-UG

Description,

Magnetic

installation

Tape

instructions,

Transport

and operating

User’s

procedures for

Guide

the TU78.

TU78

EK-1TU78-TM

Schematics and

Magnetic

logic prints

Tape

of TU78

Transport

Technical
Manual;
Volume 1

TU78

EK-2TU78-TM

Description,

Magnetic

installation,

Tape

operation,

Transport

theory, and

Technical

maintenance

Manual;

of TU78E

Volume 2

INTRODUCTION

Document
Title

Number

TMT78

EK-TM78-IP

Contents
Exploded views and

parts lists of TM78

Magnetic
Tape

Transport IPB

872 Power

EK-00872-1IP

Exploded views and

parts lists of 872

Controller
IPB

874 Power

EK-00874-1P

Exploded views and

parts lists of 874

Controller
IPB

RH20

EK-RH20-UD

Description of

MASSBUS

RH20 MASSBUS

Controller

controlier

Unit
Description

RH780

EK-RH780-TD

Programming and
theory of RH780
MASSBUS adapter

MP01061

Engineering drawings

MASSBUS
Adapter

Technical
Description

Field
Maintenance
Print Set

for TU78 mechanics
and cabinet,
engineering drawings

and parts lists for
TMT78 mechanics

and logic, TM78
power supply chassis,
+5 volt regulator,
+15 volt regulator,
and —5 volt regulator

INTRODUCTION

1.11 SYSTEM DIAGNOSTICS
The following are system diagnostics for both the
TU78 and TM78.

Diagnostic Name

Title
A.

Control

DECSYSTEM-20

VAX

DFTUI

EVMAE

DFTUJ

EVMAA

Logic Test

Data
Reliability

2.1

INTRODUCTION
This chapter gives a short description of the tools
available for troubleshooting a failure in the subsystem.
They include troubleshooting flows, on-line and in-line
diagnostic programs, error log summaries, status indicators, and a maintenance panel for exercising the formatter/transport off-line.

2.2

ON-LINE DIAGNOSTICS

2.3

IN-LINE DIAGNOSTICS

2.4

ERROR LOGS

Table 2-1 lists and describes the on-line (system level)
diagnostics available for each hardware family.

A total of 37 in-line microdiagnostics run continuously
when the subsystem is idle. If a microdiagnostic fails to
operate correctly, the TM78 raises an attention interrupt
to the host CPU(s). Each microdiagnostic may be called
up individually for scope loops or repair verification.
This is done through the TM78 maintenance panel.
Table 2-2 lists each microdiagnostic and its test number.

All DEC operating systems, under which the TU78
runs, support an error logging scheme. At a minimum,

all MASSBUS registers are read and stored away each
time a hard or uncorrectable error occurs. MASSBUS
registers are listed in Appendix A. As an error log option,
the extended sense summary may also be read and stored
away. The extended sense summary is a 60-byte field of
internal TM78 and TU78 registers. Extended sense tables for each of four possible TU78s are updated after
each error. The extended sense bytes are listed in Appendix B.

2.5 STATUS INDICATORS FOR
TROUBLESHOOTING

In addition to the TM78 maintenance panel, a total of

29 LED indicators are available for troubleshooting.

Table 2-3 lists each indicator, its function, and location.
24

TROUBLESHOOTING
Table 2-1

TM78/TU78 Diagnostics

DECSYSTEM-20

VAX

Description

EVMAE

The Control Logic Test
tests MASSBUS controller
and TM78 formatter logic.
It also tests subsystem basic
command functions while
checking for proper tape
motion timing. The test must
be run from each CPU
separately, through both
MASSBUS ports {if dual port
option is present). The test

Control Logic Test

DFTUI

provides error information

to the user via console or
lineprinter.
Data Reliability

DFTUJ

EVMAA

The Data Reliability Test
tests TM78 circuitry by
writing and reading predetermined data patterns and
recording modes. The test
provides error information to
the user via console or

lineprinter. The test may be
run in dual port mode (from

dual CPUs) driving two or
more transports.

2.6

ERROR CODES
The TM78 sends an interrupt code and a failure code
to the host CPU at the completion of any command.
These same codes are put into the maintenance display
at the completion of a command issued through the
maintenance keypad. Table 2-4 lists each interrupt code
in numerical order followed by each failure code that
could occur within that interrupt code.
Note that certain interrupt codes imply that the command completed without error or a nondata record was
found (codes 01-06). Others indicate that the transport
was not in the correct state to operate on the command,
or that another command is necessary (codes 07-27).
Still others indicate a possible hardware or software failure (codes 30-32). Interrupt code 77 is a unique code in

that it applies only to keypad commands.

TROUBLESHOOTING

Table 2-2

In-Line Self-Test Microdiagnostics

Test

Number

Description

Write microcontroller self-test (M8959)
Translator ROM parity test (M8958)

Read path microcontroller self-test (M8953)
Read channel 0 (slot AB12) self-test

Read channel 1 (slot AB13) self-test

Read channel 2 (slot AB14) self-test

Read channel 3 (slot AB15) self-test

Read channel 4 (slot AB16) self-test

Read channel 5 (slot CD13) self-test

Read channel 6 (slot CD14) self-test

Read channel 7 (slot CD15) self-test

Read channel P (slot CD16) self-test

14
15

Read path error corection self-test (M8951)
Microcomputer RAM memory self-test (Loc

Microcomputer RAM memory self-test (Loc

40000-40777)

41000-41777)
42000-42777)
43000-43777)

Microcomputer RAM memory self-test (Loc
44000-44777)

Microcomputer RAM memory self-test (Loc

45000-45777)
23

Microcomputer RAM memory self-test (Loc

46000-46777)
24

Microcomputer RAM memory self-test (Loc

47000-47777)
25

26
27

30
31
32

Loop write-to-read at TU port 0 in GCR
Loop write-to-read at TU port 0 in PE

Loop write-to-read at TU port 1 in GCR
Loop write-to-read at TU port 1 in PE

Loop write-to-read at TU port 2 in GCR
Loop write-to-read at TU port 2 in PE

Loop write-to-read at TU port 3 in GCR

Loop write-to-read at TU port 3 in PE

Loop write-to-read at MIA 0 in GCR

Loop write-to-read at MIA 0 in PE

Loop write-to-read at MIA 1 in GCR

Loop write-to-read at MIA 1 in PE

Loop write-to-read at MIA 2 in GCR

Loop write-to-read at MIA 2 in PE

Loop write-to-read at MIA 3 in GCR

Loop write-to-read at MIA 3 in PE

TROUBLESHOOTING

Table 2-3

Troubleshooting Indicator Functions
Possible

Indicator

Number
on Figure

1-3

Function

Failing
FRU

A channel has failed.
These nine indicators

e
e

TU78 transport
TU Bus cable (n)B

MB951

TU bus cable (n)A

H7490

reflect the quality

MEB950

of the data stream
for each channel or
track. They indicate

loss of SYNC or track
dropout. Nonlatched

1-3

A parity error has

occurred in the ECC
microcontroller.
Latched

1-3

There hasbeena TU
bus status parity
error. Wrong Parity

e
o

TU78 MIA
MB8955

was received at the
TU port on the WCS
lines. Latched

1-3

—5Vforthe
MASSBUS
transceivers is out

e
e

H7422
TM78 backplane

of specification.

Nonlatched

1-3

Wrong parity was

MASSBUS cable

RHXX controller

MASSBUS portona
control bus command
write. Latched

MS8957

A parity error has

MS8958

MZE959

received at the

occurred in the
translator microcontroller. Latched

1-3

A parity error has
occurred in the write
microcontroller.
Latched

*The normal state of the indicator is off.

TROUBLESHOOTING

Table 2-3

Troubleshooting Indicator Functions (Cont)

Indicator

Possible

Number

Failing

on Figure

Function

FRU

1-3

A parity error has
occurred in the

M&960

microcomputer

program ROM.
Latched

1-8

45 Vregulator 2 is
ok (supplies TM78
read path).

e
e

H7441
Any module in
slots 10<<16

1-8

10F +5 V regulator 4 is
ok (supplies TM78
write path,

e
e

H7441
Any module in
slots 1<<9

MASSBUS ports TU

ports and microcomputer.

1-8

11T —5 Vregulator 1
is ok.

H7490
M8956 (slot 1
or 3)

MEB957 (slot 2

or 4)
1-8

127 + 15 V regulator 3
is ok.

137 — 15 V regulator 3
is ok.

14t Power is being

H7476

Any M&950

H7476

Any M8950

H7422 circuit
breaker tripped

applied to the H7422

H7422 power cord

H7422 supply

157 A command or
command address on
the WCS lines was
received at the MIA
with wrong parity.

TU bus cable (n)A

167 MIA PCBA mainte-

power supply.

MREI955

TU78 MIA

Flip switch to

nance switch S4 is in
MANUAL position.

*The normal state of the indicator is off.
TThe normal state of the indicator is on.

AUTO

TROUBLESHOOTING

Table 2-4 Interrupt Code to Failure Code
Int

Code

Name

Failure Code

DONE*

00 —

Extended sense data not
updated

01 —

Extended sense data
updated and contains
something of interest

TAPE MARK*

Always zero

BOT*

01 —

EOT*

Command was issued with
tape at BOT

02 —

Saw BOT indicator after
tape motion started

03 -

ARA ID detected

00 -

Extended sense data not
updated

01 —

Extended sense data
updated and contains
something of interest

LOGICAL EOT{

Always zero

NO OPf

Always zero

REWINDINGT

Always zero

FPT*

Always zero

NOT READY*

01 —

TU is on-line but not
ready (Possible when TU
is manually rewound or
loading)

02 —

Fatal error has occurred
and this command cannot
be performed until error
status has been presented
and a TM CLEAR received

*The interrupt code is used for nondata transfer or data
transfer.

1The interrupt code is used for nondata transfer only.

TROUBLESHOOTING

Table 2-4

Interrupt Code to Failure Code (Cont)

Int

Code

Name

Failure Code

03 — AccesstoTU is allowedbut TU
is either rewinding or doing a

DSE from another MASSBUS
or keypad command

NOT AVAIL*

Always zero

OFF LINE*

Always zero

NOT
EXECUTABLE*

Always zero

NOT CAPABLE*

01 — No record found within 25 ft
(7.6 m) of tape

02 — ID burst neither PE or GCR

03 — ARA ID not found
04 — No GAP found after ID burst

(PE) or ARA ID burst (GCR)

ON LINE}

Always zero

LONG REC]

00 — Extended sense data not
updated

01 — Extended sense data updated

and contains something of
interest

SHORT RECY

00 — Extended sense data not
updated

01 — Extended sense data updated

and contains something of
interest

RETRYY

01 - CRC error, ACRC error,
pointer mismatch, uncorrect-

able or two-track error set in

ECCSTA register (This code
generated by write GCR
operations)

TROUBLESHOOTING

Table 2-4

Interrupt Code to Failure Code (Cont)

Int

Code

Name

Failure Code
- CRC error, ACRC error or
02

uncorrectable set in ECCSTA
register (This code generated

by read GCR operations)
03
- Uncorrectable error set in

ECCSTA register (This code
generated by read PE operations)

— AMTIE, pointer mismatch,
04
uncorrectable, two-track error
or single-track error set in

ECCSTA register (This code
generated by write PE operations)

05
- Atleastone bitsetin ECCSTA
register

06
- At least one write fail bit set in
RPFAIL and RPATH registers
(This code generated by write
PE operations)

07
- More than one write fail bit setin

RPFAIL and RPATH registers
(This code generated by write
CR operations)
10
- RSTAT contains bad code
11-

GCR characters from WMC
and RMC do not match ( This
code generated by write PE

The interrupt code is used for nondata transfer or data transfer.

=8
3 -}

operations)

The interrupt code is used for nondata transfer only.

The interrupt code is used for TM78 initiated.
The interrupt code is used for data transfer.

TROUBLESHOOTING

Table 2-4

Interrupt Code to Failure Code (Cont)

Int

Code

Name

Failure Code
12 — MASSBUS data bus parity
error (write)

13 — Record length incorrect during
retry opposite attempt; invalid
data has been transferred

14 — Tape positioned at or beyond
EOT.

READ OPPf

Same as Int Code 22

UNREADABLE(

Same as Int Code 22

ERROR(

Same as Int Code 22

EOT ERROR]

Same as Int Code 22

BAD TAPE*

Same as Int Code 22

TM FAULT A*

01 — Illegal command code

02 — Data transfer command issued
while nondata transfer
command in progress on same
tape unit

03 - WMC error; check ECODE
(ERR CNT register — U
address 326) register for reason
— may be Illegal Format or
Skip Count codes

04 — RUN not received from
MASSBUS controller

05 — Command from read microcontroller loopback register

did not match command loaded
into RMC CMD register.

06 — ECC ROM parity error
(M8951)

07 - XMC ROM parity error
(M8958)

TROUBLESHOOTING

Table 2-4
Int

Code

Interrupt Code to Failure Code (Cont)

Name

Failure Code
10 — Command read from RMC
register RCMLP did not match

command loaded into RCMD
register (this code generated
when Verify ID Burst command

loaded during write of BOT
area)

11 — Command read from RMC
register RCMLP did not match
command loaded into RCMD

12 — Command read from RMC
register RCMDP did not match
command register (this code

generated when Verify ARA
ID command loaded during
write of BOT area)

13 — Command read from RMC
register RCMLP did not match

command loaded into RCMD
register (this code generated
when Verify Gap command
loaded during write BOT area)
14 — Command read from RMC
register RCMLP did not match
command loaded into RCMD
register (this code generated

when Read ID Burst command
loaded during read of BOT

The interrupt code is used for nondata transfer or data transfer.

=%
g -}

area)

The interrupt code is used for TM78 initiated.

The interrupt code is used for nondata transfer only.
The interrupt code is used for data transfer.

TROUBLESHOOTING

Table 2-4
Int

Code

Interrupt Code to Failure Code (Cont)

Name

Failure Code
—
14

Command read from
RMC register RCMLP
did not match command
loaded into RCMD
register (this code
generated when Read

ID Burst command
loaded during read
of BOT area)
15— Command read from RMC

command loaded into RCMD
register (this code generated

when Verify Gap command
loaded during read of BOT
area)
17
- Command read from RMC

command loaded into RCMD
register (this code generated
when Find Gap command

loaded during Erase Gap
routine)

20
- WMC LEFT

failed to set in

Extended Sense routine
21
- PE parity error on data as it

leaves translator (checked at
translator output).
22
- XMC DONE did not set

(M8958, M&8959)
23
- WMC ROM PE or RD PE set

in WMCERR register

(M8959, M8952, M&951)

TROUBLESHOOTING

Table 2-4

Interrupt Code to Failure Code (Cont)

Int

Code

Name

Failure Code
22 —

XMC DONE did not set
(M8958, M8959)

23—~

WMCROM PE or
RD PE set in

WMCERR register

(M8959, M8952,
M8951)

TU FAULT A*

01 — TU status parity error (MIA)
02 — TU command parity error
(M8955)

03 — Rewinding tape went off-line

04 — Tape went not ready during
DSE

05 — TU CMD status changed
during DSE

06 — Capstan did not reach velocity
within 2 ms forward or 4 ms
reverse

07 — TU velocity drifted after up to
speed and writing started
10 — TU CMD did not load correctly
to start tape motion in selected
function routine (example: on
forward (write) — looks for
forward, write, and motion: on
reverse — looks for reverse and
motion)

11 — TU CMD did not load correctly
to set drive density

12 — TU CMD did not load correctly
to start tape motion to write
BOT ID Burst

13 — TU CMD did not load correctly
to backup tape to BOT after
failing to write BOT ID

14 — Failed to write density IID Burst
correctly. Looks for 256
correct samples out of 1200

The interrupt code is used for nondata transfer or data transfer.

TROUBLESHOOTING

Table 2-4

Interrupt Code to Failure Code (Cont)

Int

Code

Name

Failure Code
15
- Failed to write ARA Burst

correctly. Looks for 1/4 inch
perfect characters in ARA
burst.

16
— Failed to write ARA ID

correctly. Looks for 1/4 inch
perfect out of 2 inches
17— ARA error bit set in MTA

status B register
21
- Could not find a gap after the

ID code was written correctly
22
— TU CMD did not load correctly
to start tape motion to read ID
Burst

23
- Time-out looking for BOT after

detecting ARA ID burst
24
— Failed to write tape mark
correctly
25
- Velocity checks passed, but

tape never came up to speed
while trying to reposition for
retry of writing tape mark

26
— TU CMD did not load correctly
to start tape motion in Erase

Gap routine
27
- Could not detect a gapin Erase
Gap routine. Gap must be at
least 0.2 inch blank tape on 7
tracks (AMTIE’s — 1.6 ms)
30
~ Could not detect a gap after
writing record

- Read path terminated before
31
entire record was written. Less

than 937 byte count = erase
problem. Greater than 937 byte

count = erase/write problem
or bad spot on tape

TROUBLESHOOTING

Table 2-4

Interrupt Code to Failure Code (Cont)

Int

Code

Name

Failure Code
32 — Could not find a gap after
writing record and read path
terminated early. Starts looking
for gap 0.15 inch before end of
record

33 — TU CMD did not load correctly
to backup for retry of write tape
mark

34 — TU lost velocity in reverse
while trying to reposition for
retry of writing tape mark

35 — TU CMD did not load correctly
to backup to retry a read of
BOT ID

36 — Time-out looking for BOT after
failing to write BOT ID

37 — TU velocity changed while
writing PE gap before starting
to write record

40 — TU CMD did not load correctly
to set PE tape density at start
of write BOT ID burst

41 — TU CMD did not load correctly
to set GCR tape density after
writing Density ID

42 — TU CMD did not load correctly
to set PE tape density at start

of read from BOT

43 — TU CMD did not load correctly
to set GCR tape density after
reading a GCR Density 1D
burst

TROUBLESHOOTING

Table 2-4

Interrupt Code to Failure Code (Cont)

Imt

Code

Name

Failure Code
43 — TU CMD did notlcad correctly
to set GCR tape density after
reading a GCR Density 1D
burst

00 — RSTO interrupt occurred with

)

TM FAULT B

TM RDY still set(AC/DC LO)
01 — Power failed interrupt

02 — 8085 interrupt for unknown
reason on channel 5.5

03 — 8085 interrupt for unknown

reason on channel 6.5
04 — 8085 interrupt for unknown
reason on channel 7
05 — 8085 interrupt for unknown
reason on channel 7.5

06 — CAS retry count expired

(greater than 255)
07 — CAS contention received but
not legitimate

10 — Queue error; could not find
queue entry

11 — 8085 queue entry already full
12 — 8085 ROM parity error

13 — In-line test O; WMC (write
microcontroller) self-test failed
=M8959-M&957
14 — In-line test 1; XMC ROM

{translator microcontroller)

parity error M8958-M&8959M8960
15 — In-line test 2; RPM (read path
microcontroller) self-test failed

M8953-M8960

16 — In-line test 3; RPM1 channel
O
self-test failure M8950 (slot
AB12)

TROUBLESHOOTING

Table 2-4 Interrupt Code to Failure Code (Cont)
Int

Code

Name

Failure Code

17 — In-line test4; RPM1 channel 1
self-test failure M8950 (slot

AB13)

5; RPM1 channel 2
20 — In-line test
self-test failure M8950 (slot
AB14)

21 — In-line test 6; RPM1 channel 3
self-test failure M8950 (slot
AB15)

22 — In-line test 7; RPM1 channel 4
self-test failure M8950 (slot

AB16)

23 — In-line test 10; RPM1 channel
5 self-test failure M8950 (slot
CD13)

24 — In-line test 11; RPMI1 channel
6 self-test failure M8950 (slot
CD14)

25 — In-line test 12; RPMI1 channel
7 self-test failure M8950 (slot
CD15)

26 — In-line test 13; RPM1 channel
P self-test failure M8950 (slot
CD16)

27 — In-line test 14; RPMI1 error
correction self-test M8950M8951-M8953

30 — In-line test 15; 40000 —-40777
RAM memory failure M8960

=8 g

31 — In-line test 16; 41000 —-41777
RAM memory failure M8960

The interrupt code is used for nondata transfer or data transfer.
The interrupt code is used for nondata transfer only.
The interrupt code is used for TM78 initiated.
The interrupt code is used for data transfer.

TROUBLESHOOTING

Table 2-4 Interrupt Code to Failure Code (Cont)
Int

Code

Name

Failure Code
- In-line test 16; 41000 —
31

41777 RAM memory
failure M8960
- In-line test 17; 42000 - 42777
32

RAM memory failure M8960
33
- In-line test 20; 43000 -43777

RAM memory failure M8960
— In-line test 21; 44000 — 44777
34

RAM memory failure M8960
35
- In-line test 22; 45000 - 45777

RAM memory failure M8960
36
— In-line test 23; 46000 - 46777

RAM memory failure M8960
37
- In-line test 24; 47000 - 47777

RAM memory failure M8960
* 40
— In-line test 25; loop write-to-

read at TU port 0 - GCR
* 41
- In-line test 26; loop write-to-

read at TU port 0 — PE
*42
— In-line test 27; loop write-to-

read at TU port 1 — GCR
*43
- In-line test 30; loop write-to-

read at TU port 1 — PE
— In-line test 31; loop write-to*44

read at TU port 2 — GCR
* 45 In-line test 32; loop write-to-

read at TU port 2 — PE
* 46
— In-line test 33; loop write-to-

read at TU port 3 — GCR
*47
- In-line test 34; loop write-to-

read at TU port 3 - PE

TROUBLESHOOTING

Table 2-4 Interrupt Code to Failure Code (Cont)
Int

Code

Name

Failure Code
T 50 — In-line test 35; loop write-toread at MTA 0 - GCR

T 51 — In-line test 36; loop write-toread at MTA 0 - PE

t 52 — In-line test 37; loop write-toread at MTA 1 — GCR

T 53 — In-line test 40; loop write-toread at MTA 1 - PE
Tt 54 — In-line test 41; loop write-toread at MTA 2 - GCR
T 55 — In-line test 42; loop write-to-

read at MTA 2 - PE
T 56 — In-line test 43; loop write-toread at MTA 3 — GCR
t 57 — In-line test 44; loop write-to-

read at MTA 3 - PE
34

MB FAULT

01 — Control bus parity error
(Write)
02 — Illegal MASSBUS register
referenced

KEY FAIL

01 — Keypad entry error
02 — TM78 not off-line

03 — Illegal instruction code
%

The interrupt code is used for nondata transfer or data transfer.

The interrupt code is used for nondata transfer only.

TROUBLESHOOTING

2.7

TM78 MAINTENANCE PANEL

A firmware driven TM78 maintenance panel provides

access to the operational microcode functions, internal
hardware registers, and the resident microdiagnostics.
A table of instructions may be created in RAM

through the keypad to exercise the formatter or a single
tape transport. Many functions of the maintenance panel
can be used while the TM78 is on-line and performing
tape operations for a host CPU. Added maintenance
functions are provided when the TM78 is switched offline from the host.
NOTE

Because the operational microcode must timeshare or interleave the host commands and the
maintenance commands, use of the keypad
while on-line causes slower response time to the
commands issued by the host. Therefore, be
sure to check with the system operator before
using the maintenance panel to see if this latency is acceptable. If not, use the instruction
delay in parameter item No. 2 (Table 2-6).

The maintenance panel includes a 20-key keypad and
a 6-digit octal display cluster. Figure 2-1 shows a detailed view of the maintenance panel.

2.7.1

Keypad Function Summary

The following is a summary of the keypad functions.

Miscellaneous Keys

ENA

CLR

Pressing this key once enables
the keypad. Pressing this key
again disables the keypad.

CLEAR erases a number in the

display and stops a looping command.

TROUBLESHOOTING

TEN THOUSANDS

HUNDREDS

HUNDRED
THOUSANDS (MSD)

THOUSANDS

UNITS (LSD)

TENS

MASSBUS
ADDRESS
DIP SWITCH

MASTER RESET

EO N

PUSHBUTTON

PORT A ON/OFF-LINE

PORT B ON/OFF-LINE

Figure 2-1

TM78 Maintenance Panel

Numeric Keys

0—7

The eight numeric keys specify
one of the following before a con-

trol or operation key is pressed.
Memory address
Memory data
Internal I/O hardware address

Internal I/O hardware data
Parameter item number

Parameter data

Instruction item number
Instruction op-code
Control Keys

INS

The

INSTRUCTION key is
used to examine and modify any
of the sixteen instruction locations.

TROUBLESHOOTING

HDW

The HARDWARE key is used

to examine and modify most of

the 377 TM78 internal I1/0O registers. (Appendix B of the TM78
Technical Manual.)
PAR

The PARAMETER key is used
to examine and modify the set of
parameter items that control the
microcode in performing maintenance functions.

MEM

The MEMORY key is used to
examine and modify locations
within the microcomputers mem-

ory space.

NXT

The NEXT key causes the next
sequential item or location of the
group (INS, HDW, PAR, or
MEM) selected last to be examined.

DEP

The DEPOSIT key is used to
modify the contents of an item or
location.

Operation Keys
EXE

The EXECUTE key is used to
execute a single maintenance instruction one time only.

REP

The

STA

The START key initiates the execution of instructions previously
deposited into the instruction

REPEAT key causes a
single maintenance instruction
code to be executed repeatedly.

item group.

TROUBLESHOOTING

The CONTINUE key may be

CON

used

continue

the

mainte-

nance instruction program at the
item number saved when it was
last stopped.
2.7.2

FErrors

An error code is displayed whenever a command cannot be performed. Table 2-5 lists all the error codes and
the reason for the error.

Table 2-5

Keypad Error/Status Codes

Code in

Display

E 001

Meaning

Value of item number or location is too large for
this group.

E 002

Value of item number or location is already at
high limit when NXT key was pressed.

E 003

No numeric value was specified before deposit.

E 004

Privileged function is requested (such as
modifying a RAM or hardware location) with
TM78 on-line.

E 005

E 006

ROM address is not in use.

lllegal instruction code is selected for an
instruction item.

77 - 01

Error is detected when attempting to execute a

maintenance instruction to a TU78. Either the
TU78 selected by parameter item O is not in
maintenance mode (port select 3), or the
adjustment selected is out of acceptable
tolerance.

77 - 02

Privileged maintenance instruction is requested
with TM78 on-line.

77 - 03

Illegal instruction code is spe‘cified when using

EXE or REP keys.

2.7.3

TROUBLESHOOTING

Parameters

Table 2-6 lists each parameter location and a description of how it conditions or affects the hardware when
running maintenance panel instructions.

Table 2-6
[tem

Parameter [tems

Read/

Number Write
0

R/W

Initialized
Value

Description

000

MASSBUS Port/Tape unit
port select

This item selects one of

two MASSBUS ports and one
of four Tape unit ports
to communicate with.

MASSBUS A

MASSBUS B

et (T

Selected

TU Port 0

Lo DD

oo
D

Value

e
S
G, B

Port

Bit

TU Port 2

TU Port 1

TU Port 3

This item corresponds to
hardware register 340-W.
|

R/W

000

Program run control

This item is used by the
STA and CON keys. When

this item is any number
other than 0, a program
can be single-stepped one
instruction at a time.

When this item is O the
program can run.

R/W

000

Instruction delay

This item is used to insert a
delay between each instruction

pass when in LOOP mode. The
larger the number the longer the

TROUB LESHOOTING
Table 2-6
Item

Parameter Items (Cont)

Read/

Number Write

Initialized
Value

Description

delay. The delay can be used to
reduce the impact on host CPU
throughput, to allow tape to
stop between instructions, etc.

R/W

000

General-Purpose counter

This counter can be

loaded, counted, and
tested by maintenance
instructions.
000

Branch status

Status byte returned by
all instructions. Used

by conditional branch
instructions.
Bit O — error

Bit 1 —end of tape
Bit 2 — tape mark
000

Interrupt code
(Table 2-5)

000

Failure code (Table 2-5)
Items 5 and 6 contain the
execute status returned

by the last tape command
or in-line diagnostic
control instruction.

Program control and
privileged instructions

return execute status but
do not write into these
parameter items. These
items make it possible

to run a program that

performs tape commands
and halts if an error is
detected. The actual

error can be identified
by examining these
parameter items after

the program halts.

TROUBLESHOOTING

Table 2-6

Item

Parameter Items (Cont)

Read/

Number Write

[Initialized

Value

Description

000

Program continue
address

The CON key uses this
item to determine next
instruction address.

R/W

In-line diagnostic
index

This item selects an
in-line diagnostic

program for maintenance
instruction 16. Refer to

Table 2-2 for a listing
of the in-line tests
available.

120

Data format and skip
,

count

Data transfer maintenance
instructions uses this
item and corresponds to
hardware register 320-W.
Initialized to image
format with a zero skip
count.

Bit

Value Description

7
6:4

—O

R/W

Not used
Format Control
11 normal
15 normal

10 compatible
AW

10 core dump

10 high-density
compatible

Image (skip count
has no effect)

10 high-density
dump

lllegal

TROUBLESHOOTING
Table 2-6
[tem

Parameter Items (Cont)

Read/

Number Write

Initialized

Value

Description

3:0
00

01
02
03
04
05
06
07
10
11-17

Skip Count
No skip
Skip 1 byte
Skip 2 bytes
Skip 3 bytes
Skip 4 bytes
Skip 5 bytes
Skip 6 bytes
Skip 7 bytes
Skip 8 bytes
Illegal

R/W

020

Write function clock
control

R/W

022

Read GCR function clock
control

R/W

023

Read PE function clock
control

R/W

020

LOOP write to read
function clock control

Items 12 — 15 are the
data loaded into the
clock control register
before the function is

performed. Refer to
hardware register 360-W
in TM78 Technical Manual

for a description of the
bit combinations.
16

R/W

005000

Write record size

This 16-bit item 1s the
byte count used by write
data maintenance instructions to determine the
size of the record
written. It is used by
read data maintenance
instructions as the
expected record size.

*[tem value is not initialized by enabling keypad.

TROUBLESHOOTING

Table 2-6
[tem

Parameter [tems (Cont)

Read/

Number Write
17

Initialized

Value

Description

000000

Read record size
This 16-bit item is

returned by read data
instructions as actual

size of record read.
20

R/W

1717777

Write data
This 18-bit item is

written into the DDR for
write data instructions.
21

000000

Read data

This 18-bit item contains
the contents of the DDR
after the last read data

instruction, if performed
in image format. It is

cleared on every read in
all other formats.
22

Last fatal interrupt code
for port A

Last fatal interrupt code
for port B

Item 23 and 24 are a
history of last fatal

interrupt code (right
justified).
24

Last fatal failure code
for port A

Last fatal failure code
for port B

Items 23 and 24 are a
history of the last fatal

failure code (left

justified).

TROUBLESHOOTING

Table 2-6
Item

Parameter [tems (Cont)

Read/

Number Write

Initialized

Value

Description

The remaining items are stored whenever the execution of a
tape unit operation results in an error. The error status in the
hardware registers is saved so that it can be interrogated by
maintenance personnel. A copy of these items exists for each
tape unit and is readable by the host CPU EXT SENSE
command.

Command code is being
executed on last error.

Interrupt code is 6 bits
right justified.

Failure code is 6 bits
right justified.

NOTE

Items 26 through 30 are written with zeros when
these locations are written as a result of the keypad
hardware dump instruction.

Items 31 — 105 are

hardware registers.

Contents

Read path write

Read path

33
34
35
36
37

R
R
R
R
R

*
*
*
*
*

2
3
20
21
22

Mark 2

End mark

.42

RC par bits

Postamble det

Data

CRC

Corrected data

ECC status

Channel O TIE bus

Channel 1 TIE bus

fail bits

diagnostic bits

Read path status
Read path CMD
AMTIE
RC done
Illegal 5-4/

*Item value is not initialized by enabling keypad.

TROUBLESHOOTING

Table 2-6

Parameter Items (Cont)

Read/
Item
Number Write

Initialized
Value

Description
Register Contents

52
53
54
55

R
R
R
R

*
*
*
*

42
43
44
- 45

Channel 2 TIE bus
Channel 3 TIE bus
Channel 4 TIE bus
Channel 5 TIE bus

56
57
60
61
62
63
64
65
66
67
70

R
R
R
R
R
R
R
R
R
R
R

*
*
*
*
*
*
*
*
*
*
*

46
47
50
60
104
110
114
240
241
300
320

Channel 6 TIE bus
Channel 7 TIE bus
Channel P TIE bus
TIE bus
AMTIE
Port Status
Read data
CAS status
CBUS status
DBUS status
WMC status

71
72
73
74
75
76

100

R
R
R
R
R
R
R
R

*
*
*
*
*
*
*
*

321
322
323
324
324
325
325
326

TU select O
TU select 1
Write data
Byte counter <<7:0>
Byte counter <<15:8>
Pad counter <<7:0>
Pad Counter <<15:8>
Ecode counter

101

326

Ecode counter

102
103
104

R
R
R

*
*
*

330
331
332

DDR/MBD A.
DDR/MBD B.
WMC Errors
Interrupt status

<T7.0>
<15:8>

105

340

106

MIA status

107

]

MIA status A

110

MIA status B

111
112

R
R

*
*

3
4

Serial NR A
Serial NR B

TU diagnostics

113

114

Retry counter

This item count of number
of retry requests given.
A zero means tape unit is
not in error recovery.

115

Retry control bits

TROUBLESHOOTING

Table 2-6
Item

Parameter Items (Cont)

Read/

Number Write

Initialized

Value

Description
Bit 5 — initial command

moved tape in reverse
Bit 6 — initial command
was a read
Bit 7 — last retry

requested was in opposite
direction of initial

command
116

TU software status
Bit 0 — DSE command in
progress

Bit 1 — rewinding
command in progress
Bit 2 — tape unit exists

Bit 3 — motion command
(NDT) in progress
Bit 4 — moved in reverse
direction last

Bit 5 — last operation
wrote on tape

Bit 6 — last record seen
was tape mark
Bit 7 — Massbus port B

issued last command
117

Transfer control word
This 1tem 1s the control
word for last data
transfer command
Bits 0—2 — write clock

select

Bits 3—-5 — read clock
select

Bits 6 — PLO bypass
Bit 7 — low read
threshold
120

Retry suppress and format
control

*Item value is not initialized by enabling keypad.

TROUBLESHOOTING

Table 2-6
Item

Parameter Items (Cont)

Read/

Number Write

Initialized

Value

Description
This item is a copy of
Massbus register
E

containing retry

suppress, format and skip.
count.

121

Keypad enable flag
This item is nonzero when
keypad is enabled.

Not used

122 —

140

HDW

o
*

*
*
*

MIA register 0, TU78
status

140

i@fifiimaflm

MIA register 0, TU CMD A
MIA register 1, MIA
status a

MIA register 1, TU CMD B
MIA register 2, MIA
status b

MIA register 2, AMTIE
loop

MIA register 3, serial

No. a

*
*

MIA register 3, threshold
MIA register 4, serial

Not used
MIA register 5, TU .

®E

No. B

MIA register 7, pattern
generator data
Not used

diagnostics

Not used
Not used

[tems 140 — 147 are
explained in Appendix C
of the Technical Manuals.

137
.

*Item value 1s not initialized by enabling keypad.

ot BOS6 RlF PNy

TROUBLESHOOTING
2.7.4

Maintenance Instructions

A table of 16 maintenance instructions may be assem-

bled and run using the INS, STA and CON keys. Single
instructions may also be executed with the EXE and
REP keys. The transport being exercised must be selected to port #3. Table 2-7 lists all available maintenance instruction codes, their description, and the parameter item codes that influence the execution of that
instruction. Tape Command (Group A), Program Control (Group B), and In-Line diagnostic control instructions (Group C) may all be run while the TM78 1s offline or on-line with the host CPU using another transport. However, privileged instructions (Group D) require
that both ports of the TM78 be placed off-line.

Maintenance Instruction Codes

Table 2-7

Controfling

Instruction
Code
A.

Description

Tape Commands (Nonprivileged)
Rewind and

unload tape
Rewind tape

Write tape

mark - PE

Write tape

mark - GCR

Space one

record forward

Space one
record reverse

Parameter l[tems
(Table 2-6)

Space forward one
record or file

Space reverse one

Erase extended

record or file

0,1
0,1

0,i,12
0,1,12

0,1,13,14
0,1,13,14
0,1,13,14
0,1,13,14
0,1

gap — PE

Erase extended

0,1

gap — GCR

Loop write-to-read

0,1,15

at TU port — PE

Loop write-to-read

0,1,15

at TU port - GCR

Loop write-to-read

0,1,15

at MIA

Loop write-to-read
at MIA PCBA - GCR

0,1,15

TROUBLESHOOTING

Table 2-7

Maintenance Instruction Codes (Cont)
Controlling

Instruction
Code

Description

Parameter [tems
(Table 2-6)

01
63
71

Write data — PE
Write data — GCR
Read forward

0,1,11,12,16,20
0,1,11,12,16,20
0,1,11,13,14,17,21

Read reverse

0,1,11,13,14,17,21

Program Control Instructions (Do Not Use with EXE/REP

Keys)

2
4

NO-OP

Halt

Increment

counter +1

Decrement

1,3

counter +1

Update parameter

0,1

items 26 through
121 with current
hardware status *

Display contents

1,3

of counter.

Display contents

1,3

of parameter item
addressed by
counter.

100 + n

Load counter

1,3

with n

(n = 0-77)

200 + x

Branch if error

1,4

status

220 + x

Branch if no error

1.4

status

240 + X

Branch if EOT

1,4

detected

260 + x

Branch if no EOT
detected

1,4

300 + x

Branch if tape
mark detected

1,4

320 + x

Branch if no tape
mark detected

1,4

Branch if counter

1,3

340 + x

not zero

360 + X

Unconditional

]

branch
* Refer to note on page 51.

x = Item number (0 to 17) of next instruction if branch condition 1s true

TROUBLESHOOTING
Table 2-7

Maintenance Instruction Codes (Cont)
Controlling

Instruction
Code
C.

Parameter [tems
(Table 2-6)

Description

In-Line Diagnostic Control Instructions

Run in-line

1,10,15

diagnostic

(Table 2-2)
Run tape speed

adjustment routine

Run start ramp
adjustment routine
Run forward stop
ramp adjustment

|
36

routine

Run reverse stop

ramp adjustment
routine

Write 13 mm
(0.5 in) record

1,3,12,147

pattern generator

— PE
44

Write 13 mm

1,3,12,147

(0.5 in) record
using pattern

generator - GCR
D.
26

Privileged Instructions (TM78 must be off-line)
-

Write continuously

0,12

at 3200 FRPI in
all tracks

Write continuously

0,12

at 9042 FRPI in
all tracks
46

Write continuously

0,3,12,147

using pattern
generator — PE
50

Write continuously
using pattern

generator — GCR

0,3,12,147

TROUBLESHOOTING

2.7.5 Sample Maintenance Routine
Figure 2-2 shows the program flow for a sample

write /read maintenance routine. This routine writes a re-

cord, reads it backward and forward, then repeats the
operation till the EOT marker is reached where the tape
is rewound. A tally of all read errors is put into the display for each tape pass. If a write error occurs, many important TM78 /TU78 registers are saved in parameter locations. Then the program halts so that these parameters
can be analyzed.
The program coding is shown below.
Instruction

Instruction

Address

Code

Description

0
|
2
3
4
5
6

7
100
61 (63)
240
214
77
211

Rewind tape
Clear counter
Write PE (GCR)
If EOT, branch to start
If error, branch to save
Read reverse
If error, branch to count

71
222
4
12
362

update
Read forward
Branch to write if no error
Increment counter + 1
Put count in display
Branch to write

)

Halt

~r.

362

Save registers f’mfié@—&% ARE
SAVEE

Branch to write after continue

Sra
2.8

TEST POINTS

The following list includes all troubleshooting test
points available on the TU78 PCBAs and the corresponding signal name.
Control M2 PCBA
TP 1 - GND
TP 2 — GND

TP 3-12 - UNUSED
TP13 - +5 V DC
TP14 — LDFO

TP15 — CLK B (100 KHZ)
TP16 — U85-2

TP17 - UNUSED
TP18 — NLDPI1

el -

TROUBLESHOOTING

START

)

REWIND

0—— COUNTER |
|

SAVE

REGISTERS

HALT

READ
REVERSE

ERROR

N
READ

FORWARD

COUNTER +1

COUNTER

—COUNTER

——

DISPLAY

}F‘
&

MA-7935

Figure 2-2

Sample Write/Read Routine

Control M2 PCBA
TP19 - CLK E (10 HZ)

TP20 -~ CLK A (1 MHZ)
TP22 - U71-6 CAPSTAN REV
TP23 — U63-6

TP24 — U66-6 NRDY
TP25 - GND
TP26 —- GND

TP27 — LDF 1

TP28 — LDF 6

TP29 — U72-11 RWS

TP30 — MAINT FUNCTION
TP31 — MAINT FUNCTION

TP32 — LDF 2
TP33 — NTAP 2

TP34 - N>80 %

TROUBLESHOOTING

Control M2 PCBA
TP35 — LDF 3

TP36 — NBOT
TP37 — STL
TP38 — NEOT

TP39 — CLK C (10 KHZ)
TP40 - TACH AMP
TP41 — LDF 5
TP42 — LDF4

TP43 — LOW TAPE SENSOR

TP44 — NLDFS

TP45 — LDS (LOAD FAULT SENSE)

TP46 — BKW
TP47 — MRL

TP48 — ABP N/O
TP49 — GND
TP50 — GND
TP51 — NPOL
TP53 — THD
TP54 — CC N/O

TP55 - CO N/O
TP56 — U146-5 UNLD
TP57 — S LIMIT N/O
TP58 — NSMRL
TP59 — TOR N/O
TP60 — VAC N/O
TP61 — T LIMIT N/O
TP62 — NINTLK

TP63 — NCCC (CLOSE CART CMD)
TP64 — SRF
TP65 — SRR
TP66 — TRF
TP67 — TRR
TP68 — THDS

TP69 — NCOC (CART OPEN CMD)
TP70 — NRSAE (REEL SERVO ENABLE)
TP71 — PNU RET
TP72 — NXFR
Read PCBA
TP 1

TP 2

TP 3-9 UNUSED

TP10 TRK 9/0 ACTIVE (CH4 & 6)
TP11 TRK 9/1 ACTIVE (CH4 & 5)
TP12-19 UNUSED
TP20 U29-11

TROUBLESHOOTING

TP21 CLEAR

TP22 ST1 CLOCKS
TP23 UNUSED
TP24 UNUSED
Write PCBA

TP 1 CLK 2
TP 2 V PED

TP 3 V STEP
TP 4 V WRT
TP 5 CLK |

TP 6 V PED AT Q27/28 WD2
TP 7-23 UNUSED
TP24 REWR (REWIND RAMP)
Capstan/Regulator PCBA
TP 1 GND
TP
2 GND
TP 3-10 UNUSED
TP11 +5 V DC

TP12 V SENSE
TP13 MOTOR CURRENT
TP14 UNUSED

TP15 +15 VDC

TP16 UNUSED
TP17 UNUSED
TP18 -15 VDC
TP19 MOTOR VOLTAGE
TP20-24 UNUSED

TP49 CAPSTAN GND

TP50 CAPSTAN GND
TP51 NFPT

TP52 ANALOG TACH
TP53 UNUSED

TP54 UNUSED

TP55 SPARES 1
TP56 CART SOL RET
TP57 VAC SOL RET
TP58 WP SOL RET

TP59 PRES SOL RET

TP60-64 UNUSED
TP65 8.5 VAC

TP66-69 UNUSED
TP70 NPORST

TP71 CART MTR (+)
TP72 UNUSED

TROUBLESHOOTING

Interconnect F1 PCBA
TP 1 S POS

TP 2 T POS 2
TP 3 TIP

TP 4 N PKSN
TP 5 EOT
TP 6 BOT
TP 7 GND

Reel Servo PCBA
TP 1
TP 2

TP 4 +36 V (T)

TP 6 TM (+)
TP 8 TM (-)
TP10 -36 V (T)
TP12 +36 V (S)
TP14 SM (-)
TP16 SM (+)
TP18 -36 V (S)
TP20 UNUSED
TP21 NTDA
TP22 NTDB
TP23 NSDA
TP24 NSDB
TP49 GND
TP50 GND
TP51 Q2 (COLL)
TP52 REEL SERVO BRAKE

TP 53 +5 V (S) TO ALL IC’S
TP54 UNUSED
TP55 TPOS
TP56 NTRRTP57 NTRF

TP58 SUM AMP OUT NDTA/B
TP59 SUM AMP OUT T/U LOOP COMP
TP60 NAE (REEL SERVO ENAB)
TP61 NTINTLK
TP62 +15 V DC
TP63 UNUSED
TP64 -15 V DC

TP65 1.25 KHZ T-WAVE GEN

TP66 SPOS

TP67 OFFSET

TP68 SUM AMP OUT SUP LOOP COMP

TP69 NSRF 1
TP70 NSRR

TP71 SUM AMP OUT NSDA/B
TP72 NSRF 2

CHECKS AND
ADJUSTMENTS

3.1

PARTS REPLACEMENT

Table 3-1 lists the corequisite check or adjustment
that must be made when replacing certain parts in the
subsystem. If a part is not listed in the table, then no corresponding check or adjustment is required.
3.2

QUICK REFERENCE ADJUSTMENT

SPECIFICATION
Table 3-2 provides a quick reference to the various

TM78/TU78 adjustment specifications. Figures 3-1 and
3-2 show the location of various controls and switches on
the
TU78 PCBAs. Figure 3-3 shows the air valves with
their test points and adjustments.

Table 3-1

Checks/Adjustments When Replacing Parts

Part
Replaced

Check or

Adjustment

Paragraph

Read/
write /
erase
head

Clean
transport
Power
Capstan

4.3.4*

6.5.1*%
6.5.5%

servo

adjustment

Read/write

6.5.7*

adjustments

Capstan

System

motor

vacuum

Takeup reel

6.5.4.1%
6.5.4.2%

vacuum

Supply
reel
motor

Read skew

6.5.7.1%

Supply reel
load speed
Tape loop

6.5.6.2%
6.5.6.4%

position

*TU78 Technical Manual (Vol I1)

CHECKS AND ADJUSTMENTS

Table 3-1

Checks/Adjustments When Replacing Parts (Cont)

Part

Check or

Replaced

Adjustment

Paragraph

Takeup

Takeup reel

6.5.6.3*

reel
motor

load speed
Tape loop

6.5.6.4%*

position

AC motor

Vacuum/

6.5.4*

pressure

Blower

System

6.5.4.1%

vacuum

Takeup reel

6.5.4.2%

vacuum

Compressor

Air bearing

6.5.4.3%

pressure

Thread block

6.5.4.4%

and cartridge
pressure

Read PCBA

PE gain

6.5.7.3%

Write

6.5.7.2%

PCBA

currents

PE gain

6.5.7.3*%

Capstan
Servo

Power
Capstan

6.5.1%
6.5.5%

PCBA

Servo
adjustments

PE gain

6.5.7.3*%

Reel

Reel servo

6.5.6*

Servo

adjustments

PCBA

Dynamic

6.6.6.1%

brake check

Preamp

PE gain

6.5.7.3*

Inter-

EOT/BOT

6.5.2%

connect

sensor

PCBA

F1 PCBA

Pack sense

6.5.3%

sensor

Tape loop
position

6.5.6.4*

CHECKS AND ADJUSTMENTS
Table 3-1

Checks/Adjustments When Replacing Parts (Cont)
Check or

Part

Replaced

Mainte-

Adjustment

Paragraph

Keypad/

3.5.1.1%

nance
panel

display power
on checks

H7441

+5V

5.7.5%

H7446

+15V

5.7.5F

H7490

-5V

5.7.5%

NOTE
The paragraph number listed is for the full procedure
found in the applicable technical manual.

*TU78 Technical Manual (Vol I1)
tTM78 Technical Manual

CHECKS AND ADJUSTMENTS

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PREAMPLIFIER

\I{{gg/i[;rgCBA
ORIENTATION (!

P6 TO

WRITEPCBA |

[

1234&56789

sesses
e
©®eeoeccbddeoc

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OQUTPUTS

Ri0 R13 R16

R19 R22 R25

R11R14 R17

H20 R23 R26

U10

READ HEAD

WRITE HEAD

CONNECTOR

CONNECTOR
MA-6866A

Figure 3-1

GCR/PE Preamp | PCBA Test Points

CHECKS AND ADJUSTMENTS

SUPPLY POSITION ADJUST

TAKE-UP POSITION ADJUST

—— PACK SENSE (LOW TAPE) ADJUST
R17

/
R22 EQT/BOT ADJUST
e

TPY

TPé O

TP4 TPS

o310

TP2 TP3

R31

121

TAKE UP GAIN
R30

REMOVE PIN 1 BEFORE

SUPPLY GAIN

INSTALLATION
MA-3681

SHR-0014-84

Figfire 3-2 Interconnect F1 PCBA
a. Early Model

R1
R30

SUPPLY POSITION ADJUST
SUPPLY GAIN

TAKE-UP POSTION ADJUST

R31

TAKE-UP GAIN

R17
/- R22

PACK SENSE (LOW TAPE) ADJUST
EOT/BOT ADJUST

TP7 oo
W1

ot
O

TP1 TP2 TP3

L© |

’

J21

REMOVE PIN 1 BEFORE
INSTALLATION
MA-3681A

Figure 3-2

Interconnect F1 PCBA

b. Current Model

CHECKS AND ADJUSTMENTS

\r_

©)

ol
i

VACUUM VALVE DETAIL

* 5

PRESSURE VALVE DETAIL
MA-3488A

Figure 3-3

Vacuum and Pressure Valve Components

Reference

Description

ZZoR=—~TIQTOOO®W
>

Table 3-3

Vacuum Valve and Pressure Valve

System vacuum test point
Reel motor connections
Butterfly valve adjustment screw

Takeup reel vacuum adjustment screw
Vacuum present switch
Takeup reel vacuum port
Tape on reel switch

Vacuum input (to pneumatic assembly)
Butterfly valve lock nut
Air bearing pressure adjustment screw
Pressure input (to pneumatic assembly)
Thread block pressure adjustment screw

Thread block pressure port
Air bearing pressure port

CHECKS AND ADJUSTMENTS

3.3

WRITE CURRENT ADJUSTMENTS

. Verify power supply voltages according to Paragraph
6.5.1.

. Load any write enabled 267 mm (10-1/2 in) tape to
BOT. Leave the transport off-line.

Set the MIA switches as follows.
S1 = FWD (right)
S2 = WRT (right)
S3 = 1600 (left)
S4 = MAN (right)

Data pattern (U196) equals all ones (all switches
|
forward)
A. Phase Encoded Write Current Adjustments

. Connect an oscilloscope to write PCBA (Figure 6-18)
test point 6. Set the scope as follows.

Vertical chl =
Horizontal =
=
Sync

1.0 V/div, ac (X10 probe)
0.2 us/div
+,Ch 1, dc

Place transport on-line. The tape starts moving
forward.

. Adjust write PCBA potentiometer R50 (PE step
time) for a 1.25 us +.1 us positive pulse width.
Place transport off-line. The tape stops moving.

. Move the scope probe to write PCBA TP3. Change
the vertical setting to 2.0 V/div, dc.
Place transport on-line.

Adjust write PCBA potentiometer R19 (PE step voltage) for a +8.75 Vdc +0 Vdc level.

CHECKS AND ADJUSTMENTS

Move the scope probe to write PCBA TP2.

Adjust write PCBA potentiometer R36 (PE pedestal)
for a +6.2 Vdc 0 Vdc level.

10. Place the transport off-line and rewind the tape to
BOT.

B. Group Coded Write Current Adjustments (Transport
Off-line, Loaded, And at BOT, Port Switch to 3)
Figure 3-4 shows the correct waveform for the pedestal

current and step current at the tape head. You may want
to use this figure as a reference. The GCR write current

adjustments involve potentiometers R39, R22 and R48 on
the write PCBA. To make these adjustments, proceed as

follows.
NOTE
Use a DVM for all measurements at TP2 and
TIP3 on the write PCBA.

Set MIA switches S1, S2, S3, and S4 to the right.

Data pattern (U196) equals all ones (all switches
forward).

Place AGC switch (S1) on the read module to the

right.

Adjust R22 toset TP3 to O V.

Adjust R39 to set TP2 to 0 V.

’

Using a 10X probe, set an oscilloscope to 100

mv/div and 0.5 us/div. Place the probe on track 5
(R13) of the GCR/PE preamp 1 PCBA (Figure
3-2).

Load a standard output tape (or a good scratch
tape) with the write protect ring in place. Place
the transport on-line to start the tape moving.

CHECKS AND ADJUSTMENTS

|
e
STEP
|

STEP

CURRENT

TIME

PEDESTAL

CURRENT

l
|

|
|

|
;
A\!

g
SHR-0047-84

Figure 3-4

Write Head Current Waveform

Adjust R39 counterclockwise (CCW) for peak
amplitude. (The pedestal write current is now at
the approximate start of the 100 percent saturation range.)

Measure and record the dc voltage at TP2.

Continue to adjust R39 CCW until the waveform
amplitude begins to decrease. (This is the approximate end of the 100 percent saturation range.)

Measure and record the dc voltage at TP2. Place

the transport off-line to stop tape motion.

Add the two voltages recorded in steps 8 and 10.
Divide this sum by 2. Record the result of the
division.

12.

Place the transport on-line and adjust R39 clockwise (CW) until TP2 is at the voltage calculated in

step 11.
.

Adjust the scope’s vertical sensitivity until the

waveform’s peak-to-peak amplitude covers the
entire screen (8 cm).

CHECKS AND ADJUSTMENTS

. Adjust R39 CCW until the peak-to-peak amplitude covers 7.6 cm (about 105 percent to guarantee media saturation). Then measure and record
the voltage at TP2.

. Set TP2 back to the voltage calculated in step 11.
Set the scope to 100 percent amplitude over 8 cm
as in step 13.

17.

18.

Adjust R39 CW until the peak-to-peak amplitude
covers 7.6 cm (about 95 percent saturation).
Adjust R22 until TP3 is at the voltage recorded in
step 14. (The pedestal step current is now set to

about the 105 percent saturation point.)
19.

Move the scope probe to TP6 on the write PCBA.
Using R48 (GCR step time), set TP6 to 350 ns
-+10 percent at the 50 percent point.

20.

Place the AGC switch back to the left position.

If any value is outside the specified range, perform this
entire If it still cannot be met, the following field replaceable units should be suspected as being defective.
The Read/Write/Erase Head
The Write PCBA
The Read PCBA

The Preamp PCBA

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APPENDIX A
SUBSYSTEM MASSBUS

REGISTERS

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APPENDICES
81

APPENDICES

Table A-1

Data Transfer Function Codes

Function

Code

(Go Bit

Included)

Name

Description

WRT CK FWD

Write Check Forward — Tape

subsystem reads one record in
a forward direction. Data is
checked in RH controller.

WRT CK REV

Write Check Reverse — Tape

WRITE PE

Write phase-encoded records

WRITE GCRTM

Write group-coded records

READ FWD

Read records forward

EXSNS

Read extended sense error log

READ REV

Read records reverse

subsystem reads one record in
a reverse direction. Data 1s
checked in RH controller.

*The recording density format is ignored unless the tape is positioned at load point. At load point, the write command specifies the recording format of the entire tape.

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APPENDICES
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APPENDICES
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APPENDICES

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APPENDICES
Table A-2

Nondata Transfer Function Codes

Function

Code

(Go Bit
Included)

Name

NO OP

Description
Generates a unique

NO OP interrupt code

Unload

Unloads tape and
interrupts

immediately
07

Rewind*

Rewinds tape and
interrupts when done

Sense T

Puts status
information into CAS

Data Security

Erases remainder of

Erased

tape and rewinds

WTM PE §

Writes phase-encoded
tape mark

WTM GCR §

SP FWD REC

Writes GCR tape mark
Spaces forward

record, stops if
tape mark
23

SP REV REC

Spaces reverse

record, stops if
tape mark or BOT
25

SP FWD FILE

Spaces forward file

(to tape mark)
27

SP REV FILE

Spaces reverse file

(to tape mark)
31

SP FWD EITHER

Spaces forward

either record or
file

SP REV EITHER

Spaces reverse
either record or

file

ERG PE §

Erases three inches
of tape, sets PE

APPENDICES

Table A-2

Nondata Transfer Function Codes (Cont)

Function

Code
(Go Bit

Included)

Name

ERG GCR §

Close File PE §

Description

Erases three inches

of tape, sets GCR

Writes two tape

marks, spaces

reverse one, sets PE

Close File GCR §

Writes two tape

marks, spaces

reverse one, sets

GCR

SPACE LEOT

Spaces forward until
two tape marks,

spaces reverse one

SPACE FWD

FILE/LEOT Il

Spaces forward to

tape mark, stops if

two successive tape

marks (logical end

of tape)

*Sometimes interrupts when rewind starts; always interrupts after tape motion has stopped.

TSense registers are valid as long as the ATTN bit is set.

fErases at least 3.05 m (10 ft) beyond the EOT marker.

§ Recording format is ignored except when tape is at load point
(BOT). It is specified by bit 1.

I Do not use after any reverse operation; the TM78 may skip
over an LEOT located where direction was reversed.

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APPENDICES
97

SLO-AL

APPENDIX B

EXTENDED SENSE BYTES

Failure code last error

Interrupt code from last error

Hardware register O; read path write fail bits

Command code being executed on last error

Hardware register 1; read path diagnostic bits

Description

Byte

Hardware register 2; read path status (Refer to
Figure B-1)

Hardware register 3; read path command loop
(Refer to Figure B-1)

Hardware register 20; AMTIES (CH 7:0)
immediate status of the AMTIE lines from the tape

drive. This is a dynamic read of the M8950 done
bits by the M8953 read path microcontroller

Hardware register 21; RC DONE (CH 7:0). This
bit will be falso if the associated M&8950 has
completed its assigned task
10

Hardware register 22; GCR-illegal 5-4, PE data
error such as no bit time phase transition

ESB #6 (RSTAT)

RMC STATUS
!

7:0

]

READ PATH MICROCONTROLLER
STATUS CODES ARE RETURNED IN

THISBYTE. TABLE B-1 IDENTIFIES
EACH CODE AND IT'S MEANING.
MA-7951

Figure B-1

Read Path Status Byte

APPENDICES

Table B-1
Status

Read Microcontroller Status Codes
Meaning

Status resulting from ECC self-test command

101
102

ECC sequencer passed self-test
ECC sequencer failed self-test

Status resulting from an M8953 self-test
103
104

Read path passed self-test
Read path failed self-test

Status resulting from an M8950 self-test command
106

Read channel tests all passed

Status resulting from a clear all test command for velocity testing of drive by microcode
1

201

First tach pulse

Last tach pulse (eleventh) (ten
spaces)

Status resulting from a sample density command
210
211
212

NOT CAPABLE found
GCR ID found
PE ID found

Status resulting from a write test of IBG, PE ID, GCR ID,

ARA ID, or ARA burst

220

Bad status (write test)

Status resulting from a tape mark test command
222

Good tape mark found on tape
status

Status resulting from a NON BOT command (read or write
FWD or REV, GCR or PE)

230

ARA ID found (nét record or TM)

231

Tape mark found

234

Preamble end not found

235

Read path fault 1, too many
M8950s have been fataled to
continue record processing

APPENDICES

100

Table B-1

Read Microcontroller Status Codes (Cont)

Status

Meaning

236

Read path fault 2; 7 or more
M8950 BOARDS found illegal 5 to
4 translations.

241

Unexpected IBG in data;
probably creased tape (7 or
more AMTIES active)

261

Postamble long

262

Postamble short

377

ESB #7 (RCMLP)

05
T

RMC CMD 7:0

]

RUN CONTINUOUS

(CODES 01-06)
THIS BYTE CONTAINS THE LAST
COMMAND SENT TO THE M8953
READ MICROCONTROLLER.
MA-7952

Figure B-2

Read Microcontroller Command Byte

Byte

Description

Hardware register 23; mark 2

(CH 7:0-RMK?2)

Hardware register 24; end mark (CH 7:0-REND)
for read channels location: M8950s

Hardware register 25; RC PAR bits (CH P) (Refer
to Figure B-3)

APPENDICES

101

Table B-2 Read Microcontmi!er Command Codes
CMD Code

Description

NOP

Interblock read

Test PE ID burst

Test GCR ID burst

Test ARAID burst

Test tape mark

06
07

Test ARA burst
Normal NON-BOT read

Run RMC self-test

Test unknown ID burst

Run read channel micro’s test

Diagnostic read command

14
15
16
17

Run read channel self-test
Run clear all RMC test program
Run ECC self-test program
Find gap

ESB #13 (RPSTA)
07

CDP

|MK2P{

NDP |

CORRECTED
PE
MARK 2
RCP
DATA
POSTAMBLE | DETECTED | NOT DONE
DETECTED

DATA BIT

END MARK

ILLEGALS5:4

AMTIE

DETECTED
MA-7953

Figure B-3

Parity Read Channel Status Byte

Byte

Description

Hardware register 26; read channel PE postamble
detect register (CH 7:0); location — M8950

Hardware register 27: data (CH 7:0). Data output
from M8950 toc ECC-M8951

Hardware register 30; CRC word. CRC checker
output bits — location: 8952

APPENDICES

102

ESB #18 (ECCSTA)

AMTIE

POINTER

OCCURRED | MISMATCH

ECC ROM

PARITY
ERROR

ACRC

SINGLE TRACK
ERROR

CORRECTION

TWO TRACK
ERROR

ERROR

CORRECTION

UNCORRECTABLE
MA-7954

Figure B-4

Byte

ECC Status Byte

Description

Hardware register 31; ECCOR. Corrected data
(CH 7:0). Corrected data output from M8951 to
ME8952

Hardware register 32; ECC status— 8951 (Refer to
Figure B-4)

Hardware register 40; channel O TIE bus (Refer to
Figure B-5)

Hardware register 41; channel 1 TIE bus (Refer to
Figure B-5)

Hardware register 42; channel 2 TIE bus (Refer to
Figure B-35)

Hardware register 43; channel 3 TIE bus (Refer to
Figure B-5)

Hardware register 44; channel 4 TIE bus (Refer to
Figure B-35)

Hardware register 45; channel 5 TIE bus (Refer to
Figure B-5)

Hardware register 46; channel 6 TIE bus (Refer to
Figure B-5)

Hardware register 47; channel 7 TIE bus (Refer to
Figure B-5)

Hardware register 50; channel P TIE bus (Refer to
Figure B-5)

2ingigG- [ouey)(N)yoea]urJolg214g

(L9JZIs-L6N3LHD#)

SL4O13I81L)5S8LI1LN9IV3LyJS1H(s0TVLLM19OdHY'HM-1

3SYHd 311

GG6L-VIN
P8-61C0HHS

0 0 1GvAvO3IdT=103]=dHOAODVPHGLHD(N)3LSN81'+=01=V11VS1‘S4SAH3AN1VVIMNHTIIOYLdI0NHIONOILdV‘YJdIdN3SHIHNNNOIO400O

LO 90 0 {ii ||n 0G &0 ¢0 L0 {i| HI! 0
APPENDICES

FILINV

103

104

APPENDICES

ESB #30 (PSTAT)

CMD | TU

wcs | RD | AMT

WDS | 5 | pres|TACH]| p

WCS STATUS
WCS
PARITY ERROR | cOMMAND

WHEN READING |
WCS LINE

TU BUS

TACHOMETER

DATA STROBE

TUBUS | TUAMTIE BUS
LINEWCSP|
PARITY LINE

“pariTy
ERROR

BUSWRITE

STAT

TAPE UNIT
PpPRESENT

LINE

RDP
MA-7956

SHR0220-84

Figure B-6

Byte
28

TU Port Status Byte

Description

Hardware register 60; RTIER. Read channel

bypass for diagnostic purposes.

Hardware register 104; TAMT. Diagnostic AMTIE

loop register in 8955 module

Hardware register 110; PORT status (Refer to
Figure B-6)

Hardware register 114

Hardware register 240; CAS status (Refer to
Figure B-7)

Hardware register 241; CBUSSTA status (Refer
to Figure B-8)

Hardware register 300; DBUSSTA status (Refer
to Figure B-9)

Hardware register 320; WMC status. See Appendix
B in maintenance manual for bit descriptions.

Hardware register 321; TU select 0. (M8955 slot
8) See Appendix B in maintenance manual for bit
descriptions.

Hardware register 322; TU select 1. (M8955 —slot
9) See Appendix B in maintenance manual for bit
descriptions.

Hardware register 323; WRTDAT. Write microcontroller data — 8959 module.

Hardware register 324; BYTCNT <7:00>. Write
byte count lo word

APPENDICES

105

ESB #32 (CASSTA)
07

TM | cas
(V|
o8
| ILR | ATA

CONT|

DS2:0
i

»l

MASSBUS

CAS

ILLEGAL

DRIVE ADDRESS

CONTENTION

MASSBUS

FOR THIS PORT

ERROR

THIS MASsBUS | ERENCED
PORT IS
READY

ATTENTION
ACTIVE

CAS/MASSBUS
C BUS PARITY
ERROR ON

WRITE TO TM

o
SHR0221-84

Figure B-7

CAS Port (N) Status Byte

ESB #33 (CBUSSTA)
07

|ms

|me

|mB

| wmB

ok | ONL

RERERN

MASSBUS

-5 VOLTS

ATTENTION|

DEMAND

FAIL

MASSBUS
TRANSFER

MASSBUS
INITIALIZE

WMC DATA
SHIFT LEFT

MASSBUS
PORT IS
ON-LINE
MA-7958

SHRQ222-84

Figure B-8

Byte

MASSBUS C Bus Status Byte

Description

Hardware register 324; BYCNT <15:8>. Write
byte count hi word

Hardware register 325; PAD CNT <7:0>. Write
microbyte assembly pad character counter lo word

Hardware register 325; PAD CNT <15:8>. Write

micro byte assembly pad character counter hi word
43

Hardware register 326; ERRCNT <7:0>. Hi

word bits 8 — 15. Write micro byte assembfiy error
code

106

APPENDICES

ESB #34 (DBUS STA)

| MB

07
MB

WREN|WCLK|

OCC | EBL | EXC|

01
|WMC

|MB

RUN | SCLK|SCLK

MASSBUS | WMC SCLK
MASSBUS
PORT WRITE|
OR
ENABLED | OCCUPIED | EXCEPTION

HARDWARE
REGISTER

300-W BIT O

MASSBUS
WRITE
CLOCK

MASSBUS
END OF
BLOCK

MASSBUS

SYNC
CLOCK

RUN

MA-7959

SHR0223-84

MASSBUS Data Bus Status Byte

Figure B-9

ESB #47 (WMCERR)
07

01
L

ROM | DR

Iwmere| ERR|pe | RDPE
MASSBUS

DATA

WMC ROM
PARITY

BUS PARITY

ERROR

WMC ERROR

00
1

IMBDI
3 BITS
HI ORDER
OF MBD LINES

READ
DATA PARITY
ERROR FROM
M8952
MA-7960

SHR0224-84

Figure B-10

Write Microcontroller Error Byte

Byte

Description

Hardware register 326; ERRCNT code <15:8>
word bits O — 17. Refer to Appendix B in maintenance manual for bit codes

Hardware register 330; DDR A diagnostic data
register A used to test bus between M8956 and

Hardware register 331; DDR B. Diagnostic data
register B used to test bus between M8956 and
M8959

M8959

Hardware register 332 WMCERR (Refer to Figure
B-10)

APPENDICES

107

ESB #48 (INTSTA)
07

| ROM|

SEL|PE

MASSBUS

PWR | WDR|

| OK

MBA | MBB

|XROM

OUT | OUT | WRPE|PE

| POWER OK | MASSBUS

PORT SELECT

0=PORT A

|PE

TRANSLATOR

PORT A

(M8959)

LOGIC NOT

ROM PARITY

1=PORT B

PRESENT

ERROR

TRANSLATOR

PE WRITE

VPE ON

DONE

MICROCOMPUTER

PE WRITE

MASSBUS

(M8960) ROM

PARITY ERROR

PORTB LOGIC
NOT PRESENT

MA-7961

Figure B-11

Interrupt Status Byte

ESB #49 (TUSTAT)
07

| RDY

rpy | on

| ONL | REW|

PES | BOT | EOT | FPT

FILE
BEGINNING
|PROTECTED
OF TAPE

TU IS
TU IS ON
LINE AND | ON-LINE
READY

BUT NOT

NESSARILY | 0=GCR MODE END OF
READY

READY WENT

| 1=PEMODE

TAPE

TU IS

REWINDING
SET SINCE
LAST TU CLEAR
COMMAND
MA-7962

Figure B-12

TU78 Status Byte

Byte

Description

Hardware register 340; INTSTA (Refer to Figure
B-11). Interrupt status byte on M8960

MIA register O; TU78 status( Refer to Figure B-12)

108

APPENDICES

Byte

Description

MIA register 1; MIA status A (Refer to Figure B-13)

MIA register 2; MIA status B (Refer to Figure B-14)

MIA register 3; SNTH. Serial number— thousands

MIA register 4; SNTU serial number — tens and

and hundreds digits (BCD)

units digits (BCD).
54

MIA register 5; diag (Refer to Figure B-15)

Retry counter (RETCNT) — This byte is the count
of retry interrupt requests given for the tape unit.
When this count is zero, the tape unit is not in a
retry sequence.

Retry control bits (RETCNT+) — This byte is used
by the microcode to control error recovery. It is
meaningful only when the retry counter (byte 55) is
not zero. (Refer to Figure B-16)

TU software status (TUx). This byte contains
information about the tape drive. (Refer to Figure
B-17)

Transfer control word (XFRCTL) — This byte
contains control information used by data transfer
commands. (Refer to Figure B-18)

Retry suppress and format control (XRETRY).
This byte contains the contents of the left half of the
MASSBUS register (CAS register 2), which
contains the SER (Supress Internal Error

Repositioning) bit, format, and skip count.
60

Keypad enable flag (ENAON) — This byte is not
zero when the keypad is enabled.

109

APPENDICES

ESB #50 (MIA STAT A)
07

MAN

17 | FWD | REV | WRT | | W\ | LWR | MOT | DSE

MIA IS IN

MANUAL

| REVERSE

TEST MODE

WRITE

HEAD

CAPSTAN
MOTION

INHIBIT

TU
FORWARD

WRITE
COMMAND

DATA SECURITY
L0OP

ERASE

WRITE-TO-READ

TEST COMMAND
MA-7963

Figure B-13

MIA Status A Byte

ESB #51 (MIA STAT B)
07

CMD
oe

TUBUS

COMMAND

ARA

PEC | crp|

ERROR

01
T

| AUTOMATIC

PARITY

00
f

P(I)RT SEIL

‘

READ

|AMPLIFICATION
BURST ERROR

0= GCR MODE
1= PE MODE

PORT SELECT

SWITCH POSITION

’

6= POSITIONO
5= POSITION 1

2
3= POSITION

7= POSITION 3

MA-7864

Figure B-14

MIA Status B Byte

110

APPENDICES

ESB #54 (TUDIAG)

DET TACH|
WRB4| WR |RDEN EOT

THR, 1:0

AMTIE
|
TACHOMETER THRESHOLD
L

—

PULSE

ENABLE

WRITE

AMTIE
1

l
READ

]
STATE OF

TK4

3=20% READ

NOT WRITING

EOT
DETECTED
MA-7965

Figure B-15

MIA TU Diagnostics Byte

ESB #56 (RETCNT+1)
07

OPP

RD | REV

INITIAL
LAST RETRY|
WAS IN THE | COMMAND

OPPOSITE |MOVED TAPE
DIRECTION OF] REVERSE
INITIAL

COMMAND
INITIAL

COMMAND
WAS A READ
MA-7966

Figure B-16

Retry Control Byte

APPENDICES

111

ESB #57 (TUX)

PORT|

WRT | REV | NDT | PRES|

LAST
RECORD

REW | DSE

TAPE WAS | TU EXISTS

DATA
AND POWER | SECURITY

LAST

MOVED

WAS A

IN REVERSE

TAPE MARK

PROGRESS

NON-DATA

REWIND IN

O= LAST MASSBUS

TRANSFER
COMMAND

COMMAND CAME

ISSUED FROM

FROM PORT A

ERASE

IS ON

SEEN

PROGRESS

A MASSBUS

1= LAST MASSBUS

PORT IS

COMMAND CAME

IN PROGRESS.

FROM PORT B

LAST TAPE
OPERATION
INVOLVED A

WRITE TO TAPE
MA-7967

SHR0225-84

Figure B-17

TU Software Status

ESB #58 (XFRCTL)
07

04
¥

[;;O
.

READ CHANNEL

00
i

WRC SEL 2:0

}

01
H

RDC SEL 2:0
|

03
T

1
I

|
g

WRITE CLOCK SELECT

0= NORMAL WRITE CLOCK

PHASE LOCK

1= +20% CLOCK

OSCILLATOR
BYPASS

2=+10% CLOCK (GCR READ)
3=-20% €LOCK (PE READ)
4= EXTERNAL CLOCK

5= SINGLE STEP

6/7= NOT USED
READ CLOCK SELECT

0=-10% CLOCK
1= +10% CLOCK
2= NORMAL CLOCK

3=-30% CLOCK
4= EXTERNAL CLOCK
5= SINGLE STEP

8/7= NOT USED
M&-7968

SHRQ226-84

Figure B-18

Transfer Control Byte

REMOTE

fi...._.,__m_.___..__..___._m__._.________________,_______________________________

SWITCHING
CONTROL BUS
FROM CPU (
ON/OFF)
POWER

|
i TM78

V8960

I
|

PROM
16 K

———

—1 CAS

,
i'l\"/is 59 U

cPuB| Y

|| [vesss
ASsBUSBL|

HASSBUS

CONTROL

<: BUS

BUS
Cens

BUS

M8952

Dl XLATOR

1 EK/l8951

I l

CRC/ACRC

FIFO

uC |

ECC

l M8953
|

SEAD PATH

DATA PATH[® J5JuC
FIFO
XLATORS
R

g 171

J =-

CEEmGED MtTma CCOwnm CHSmNny (WO

ey CEITmmEE) CESmmes)

(6 TO 4)

TU BUS O
J

—.

b mom— J

| GRS

TUBUS 3

n TU782 4 !

/ooTTm

—>
MIA

l
I

DRIVE

pres| -MIT

CONTROL
MANUAL
LOGIC &

CONTROLS

WRITE
DATA
READ DATA

AUTOLOAD

READ/WRITE

COMMANDS |TAKE UP REEL e

SERVO

VAC/
PRES

‘

COMMANDS | < ovo

MOTION

TAKE

3TAPE
:
SWITCH

FROM READ HEAD

| | |PUCKERTMSNY -

UP SERVO FEEDBACK

|L e

LIMIT

CAPSTAN

SUB SYSTEM

—

E\Ng\xe

TAKE UP REEL

CAPSTAN DRIVE

TACHOMETER OUTPUT
VAC/PRES

SWITCH

I
I

|
SUPPLY LOOP

<l [ ———
__ PNEUMATIC

(BUFFER BOX) l

COLUMN

‘

capsTAN
CAPSTAN
TAKE
UP LOOPCOLUMN
TACHOMETER
MOTOR
PNEUMATIC

(BUFFER BOX)

VACUUM

Jdomr

‘

SUB SYSTEM

—

0 umiT

TO ERASE HEAD
TO WRITE HEAD

SUPPLY

TAKE UP

AMTIE STATUS | SUB SYSTEM

MOTION

———

REEL

VAC/

TU783 | E

PRESSURE
TRANSDUCER

LIMIT

SUB SYSTEM | supPLY

COMMANDS | SUPPLY REEL
SERVO

m
TU78-1 !
l

WIos)

l
I

I
l

DATA

AUTOLOAD
MOTION

_]
!

SUPPLY SERVO FEEDBACK

!——o (3)

DISTRIBUTION]| -

]

COOLING
FANS

POWER AND |REGULATED
_ |SUPPLY
DC

SUPPLY

XLATGR

vy
+5 +15
AC/DCjLOW

F\Mgo58 U

I l

AC LINE l|

H7429-AB
POWER

‘

CONTROLLER V—_“

PAD AND
DISPLAY

MASSBUS A} [vges7

INPUT POWE‘> 872/874-E
POWER

MICROCOMPUTER
»
. » |NUMERICAL

RANSPORT

| Tu7s0

ON/

SENSE

)

PRESSURE

AC LINE

ZZZ EXCHANGER ZZZZFROM COMPRESSOR
0

HEAT

==
=
MA-7934

TU78 Subsystem Detailed Block Diagram

JLITUL

CLOCK

a ER
ToorH

8
TM

||'

INTERCONNECT
DI
2

WRITE

P
OUTPUT

RRENT )

WRITE AMP OUTPUT

2323
1

PREAMP

1 ETCH

635

1 J(Pooa)

20—¢,
d

s
<

CABLE HEADER

ON PREAMP PCB

16 | 4

2 | 18|

1
0

19 | 87
20
[17]

)

|43

2,;

||
R
|

:
7 | 15
6 | 21 | «
5 | 14 | 4 | 22 | 1
:

TS
P6

[3HEAD

HEADER

WD7 1;

WDPH

16—
|
| |

CENTER TAP COMMON

TOALL WRITE HEADS

Woe | o

woa |2

|p—

"No | e

i
f——

10
20

13—

26—

—

TRACK 8§

TRACK 9§

PIN 23 (COMMON)

COMMON
CENTERTAP

;

FIGURE 6-39

WAVEFORM

'
|>—
4

TEST
: | POINT
TRACK

if
ak17
»>—
;7°

1J Ry Ro 5
2f
T |Rs | 37
jl | R4
’
R0
4 1ol | R P L P

>—18
!

5 | Rig|

>_ ,

sfl

(PO)

NO.

Rg|

J906

[«

:
|

52 1:a 25= ]
13
[ 3 [ 1937 ]!!
127 4T
:
29e | 76] a0211 | i3]
4 )|

BOT AND GCR

24Pon\ITs1

26 | P | 27 | 10p
0

6 | 22

> 8

9. | Ros | Rog | 4

8 i | Ry 2 | Rz | 0

s 1

|
||

!
!:

READPREAMP

casle

45O

evirai
it

————@- THRESHOLD
(+VAM)

HEAD

ERASE

STDTH

LEVEL PE

- NC [W-1
-

NLTH
‘——-@—
DET.

}‘%

el
—

12l:

WRITE
PATH

-4

FROM

NOT
E34"M|,—_-S USED

{

(O, P2
925FRONT|
ON

({)F WRITE |AMTIE

'..

PCB)ICABLE

)

FIGURE 6-43, 44

WAVEFORM ,

[ o oonosoooo

°°°°°°°°°°J

!
WRITE PCBA

31 MIA

2
5

6
7

P
0

Read Path Troubleshooting Diagram

EpN

1
> | 34
32

MIA
EDGE

|«—CONNECTOR

READ

|
|

MIA

PCBA

PATH

READ

PATH

7€

AMTIES

|
|

OUTPUT | PCBA

PCBA

JBPIN#
| JIPIN
&
=5 #
)

—27

6
:

3(9)

|t
!

!
j|

g;33

21
37

2 o,,o””“ooooooooooj
J3
40
0000000000 0000000000O

MIA

P
0

19
3

PO w

RADIAL
BUS
TO FORMATTER

BUS CABLE FORMATTER

DATA

WRITE

RADIAL_ TO»

¥VECSST WRITE :/—V?R(I)?E

]

AMTIE
CABLE

‘

70 ' 70—s)

RD |[J3PIN#
1
%

"
FORMATTER

17
18

J7 :| P7

oREAMP | READ

READ
ENABLE

— ——
|,
:

|
|

13
1

PATH

AMTIE [ PIN #
L

}

J.25

GCR (GAIN)
PE

l
|

10
READ

PCBA

POS : (PREAMP OUTPUT RD5) 55 ‘

BUFFER
DRIVER

INTERCONNECT D1

5 | 61
A
—s
Pl

;

READ
Ml PCBA

|
iln

.
T

= = — == 3
— A———————————————
AMTIE CABLE

|
'|!

WCS TEST
DATA
FORMATTER)
(FROM

|
:

1‘

|
|!

[

TO/FROM PREAMP -

PRE-AMP

REdD

| RIBBONCABLE | P5TOBACKPLANE EDGE CONNECTOR

READ

READ HEAD|

RDT || P569

TEST

PIN #

ST
CLOCKS

]
!

PR
EDGE
CONN.

GAIN CONTROL

FIGURE 6-40

(DRIVER)

.‘ AUTO MATIC

PE GAIN

DET.

I__l/

{ L a—acR

71 | Rig | Rao | O

>—120

14114

;

11
I

CROSS)

(ZERO PEAK

COUNTER

Rig | Ri7 | 1

et OUT':JET)

Lol
|b
|

ON READ PCB

|
ouT [OUT
2 | ||
cHAN. | ouT | ouT | RD | | AGC |PO/RD| 1

'>—16

MA-7319

Write Path Troubleshooting Diagram

(CHAN
ouT #2)1

i P902

/M/'GAIN
CONTROL 14 'u 14
A
b

14| 833 34

WAVEFORM

(CHAN 1)

R2R rovaTie

F:U—o—%
!

6,7,8,9,10,18,18,20, 21, 22

3 APROX.

TEST

;
L1

CENTERTAP TO PINS

CHé

READCABLE

b }CH4

R:
24

CENTERTAP TO PINS
2,3,4,5,14, 15, 16,17

§ :>

TRACK 6

PIN1 ON P6 (COMMON)

TRACK 7

161

10—
3l

}CH7

15 }CHz

wool 20|

TRACK 5

141
5

19—
wotl 4 | |

STACK
.1| CENTER TAP
12 }CHS
134 | pere

TRACK 3

WRITE

AMPS

TRACK 4¢

o |17

WD2

PRE-AMP

>—13
10K3 3K 1 ,
,
;
FIGURE

TRACK 2

l TP2

l
R48 {tp1 L7P3

PCB
WRITE
caBLE
1 |’ : S
Y
e 14—
wos|

‘
3WRITE

»S
'

STEP | PED

PRE.AMP

TRACK 1 | T Ti c42
56PF
3
>

WRITE

REF.

@
v

j47]
>
INTERCOMNECT
J7TOWRITE D7
37

WRITE AMP
:

TO WRITE HEAD

COMMONPIN | IWD | PIN#S

=3 Q APPROX [ 1

PCBA

CLK

;

Uss
S BV

!||

4
Z
FIGURE |Z

l|
!

P7 IWD | PIN#

WRITE HEAD

1
23
CENTERTAP | 1
TO ONE LEG | 23

|34

WRITE F/F

ES]

5 38
39
75 | 70
32 | 14142

o] CABLE

|
|

A
CENTERTAP

21 || 2322

5 ;
yL50
S

SWITCHES

FIGURE 6-36

WRITE

WD7 | PIN#

TEST DATA PATTERN

I
TM

IWDS
K pyrywasg

WRITE
TEST
CLOCK GEN

BACKPLANE

{

0sc

vwrr {77
(WRITE

:
|

IN PARALLEL

—_IwD7

INTERCONNECT D1

MA-7320