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Document:	TU77 Subsystem Pocket Service Guide
Order Number:	EK-0TU77-PS
Revision:	2
Pages:	92
Original Filename:

OCR Text

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EK-0TU77-PS-002

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Prepored by Educononol Services
of
Digital Equipment Corporation

| lst Edltlon July 1983

2nd Edltlon December 1983.

The reproduction of this material, in part or whole, is strictly

. prohibited. For copy information, econtact the Educational
*ServicesDepartment, Dlgltal Equlpment Corporatlon Maynard,
Massachusetts 01754,

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

The following are trademarks of Digital Equipment Corporation,

Maynard, Massachusetts.

dlilgliftlall]

DEC
DECmate
DECnet
DECSYSTEM-20
DECUS
DECwriter

DIGITAL

LA
MASSBUS
PDP
P/OS
Professional
Rainbow

RSTS

RSX
UNIBUS
VAX
VMS
VT
Work Processor

CONTENTS
1

INTRODUCTION
OVEIVIEW ..t e
Controls and Indicators ...................

Operator Control Panel ................

Maintenance Switch and Indicator
Functions .........

... . ..

Related Documents ......................

TROUBLESHOOTING

2.1

General

2.2.1

TMO03/TU77 Diagnostics .. ...............
Control Logic Test 1 ..................
...
Control Logic Test2 ..............

2.2.2

........ ... ... . ..,

2.2.3

Basic Function Test ...................

224

Drive Function Timer .................

2.2.5

Data Reliability

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

M8940 MTA Status Indicators .......... L
2.4

Load Faults .........
...
...
it

2.5

Load Fault Flow Diagrams ...............

2.6

Pneumatic System Troubleshooting ........

CHECKS AND ADJUSTMENTS

General .............coiiiiinn. P
Power Distribution ............ccoounnn.
Base Assembly Interconnect
3.3.1
3.3.2

3.3.3

Adjustments ........
... ... ..
EOT/BOT Adjustment ................
Tape-In-Path Sensor (Interconnect F

Only) Adjustment .............. e

Pack Sense Assembly (Low Tape
Sensor) Adjustment ...................

3.4.2

Vacuum and Air Pressure Adjustments .. ...
System Vacuum Adjustment ...........
Take-up Reel Vacuum Adjustment .. ....

3.4.3

Air Bearing Pressure Adjustment .......

3.4

3.4.1

iv.

CONTENTS

344

Thread Block and Cartridge Pressure

Adjustment ............
... .. .. ... ...
3.5

Capstan Servo Adjustments ...............

3.5.1
3.5.2

Capstan Speed Adjustment .. ...........

Start/ Stop Ramps (Forward)
Adjustment ...........................

3.6

Reel Servo Adjustments ..................

3.6.1

Reel Servo Offset Adjustment ..........

3.6.2

Supply Reel Load Speed Adjustment . . ..
Take-up Reel Load Speed Adjustment . . .

3.6.3

3.6.4

3.7

Tape Loop Position Adjustment ........
Read and Write Adjustments ..............

3.7.1

NRZI Threshold Adjustment ...........

3.7.2

NRZI Gain Adjustment ...............

3.7.3

NRZI Read/Write Skew Adjustment .

3.7.4

PE Read Threshold(Low) Adjustment . . ..

3.8
4

Interconnect D1 PCBA

. ..

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

TMO3 REGISTERS

4.1

General

4.2

Quick Reference .........................
Detailed Description ................ P

4.3

4.3.1

........
... ... .. .. ...,
..

Control Register (CS1) ................

4.3.2

Status Register (DS)

4.3.3

Error Register (ER) ...................

4.3.4
4.3.6

Maintenance Register (MR) ............
Attention Summary Register (AS) ......
Frame Count Register (FC) ............

4.3.5

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

4.3.7

Drive Type Register (DT)

4.3.8

Check Character Register (CK)

4.3.9

Serial Number Register (SN) ...........

4.3.10

Tape Control Register (TC) ............

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

........

DATA FORMATS

General

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

MASSBUS/TMO3 Transfers.........B

TMO03/Tape Frame Packing and
Unpacking ............
... oL,
Frame Packing ..... e

Frame Unpacking ..........ccovuuno...
Packing/Unpacking Formats ...........

CONTENTS

FIGURES

1-1
1-2

1-3
2-1
2-2
2-3
2-4
2-3
2-6
2-7
2-8

Basic System Configuration ...............
..
.. ...
TU77 Control Panel ..............

Maintenance Controls and Indicators ......
M8940 MTA Switches and Test Points .. ..
Load Fault O Flow Diagram
Load Fault 1 Flow Diagram
Load Fault 2 Flow Diagram
Load Fault 3 Flow Diagram
Load Fault 4 Flow Diagram
Load Fault 5 Flow Diagram
Load Fault 6 Flow Diagram

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

2-9
3-1

Pneumatic Troubleshooting Flow Diagram . ..
Capstan/Regulator PCBA Adjustments

3-2

Interconnect F PCBA Adjustments and

3-3

Interconnect F1 PCBA Adjustments and

3-4

3-5

Valve Orientation on Base Assembly
(Rear VIEW) . ..vivt it
- Control M2 PCBA Adjustments and Test

3-6
3-7

Vacuum Valve and Pressure Valve .........
Reel Servo PCBA Adjustments and Test

3-8

L PCBA Adjustments and Test Points . . .
Data

3-9

3-10
3-11
3-12

...
.. ...,
and TestPoints .......

TestPoints . ...t
TestPoints .. ...t

Points . ..ot

Points ...t

...
...
...
Forward Start Ramp ............

Forward Stop Ramp (Correct Waveform). . . ..
Forward Stop Ramp (Incorrect Waveform
Showing Overshoot) .....................
.
... ...t
Reverse StopRamp .........

3-13

Buffer Column Park Zone ( Take-up

3-14
3-15

Base Assembly, Front Components ........
Loop Travel Limits ......................

3-16

9TK Preamplifier PCBA Adjustments and

3-17

Location of NRZI Read Skew Azimuth

Column Shown)

. ...,

TestPoints .. ...

Adjustment

........ ..

3-18

IRDS Delay Character Gate ..............

3-19

Write/Deskew PCBA Adjustments and

3-20

Interconnect D1 PCBA (Front View) ......

4-1

TestPoints ................ ..., [P

TMO3 Register Contents

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

\Y,

CONTENTS

M8940 MTA Indicators ..................

..........

M8940 MTA Switches ...................

TU77 Operator Panel Controis ............
TU77 Operator Panel Indicators

l\)r—*th.p.wl\)r—-*o\w.b.w[\):-a

TABLES

Related Documents ......................

TMO3/TUTT Diagnostics .................

M8940 MTA TestPoints . ................
M8940 MTA Indicators ..................

M8940 MTA Switches ...................
Load Fault Areas ........................
TU77 Power Supply Voltage Readings ... ..
NRZI Channel Test Points and

W
=

TMO3 Registers ...........ccovvinin....
Control Register Command Function . ......

SN W

PE Channel Test Points and Adjustments . . . ..

TMA-b-{}-bw

Adjustments ............
.. ... ..
.

Status Register Bit Positions

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

Error Register Bit Indicators ..............
Maintenance Register Bit Positions

........

Effects of Writing into Attention Summary
Bit Position .............
... . ... .. .. ...
Type and Status of Selected Formatter
and Transport ...........................
Drive Type Register Bit Positions

.........

Tape Control Register Bit Positions ........
PDP-10 MASSBUS Word Format ........
PDP-11 MASSBUS Word Format ........
PDP-10 Compatibility Mode — Format

Code 0011 ...
PDP-10 Core Dump Mode — Format

Code 0000 ....... ... i,
PDP-11 Normal Mode — Format
Code 1100 ....... ..o,
PDP-11 Core Dump Mode — Format

Code 1101 ... i

1 INTRODUCTION
1.1

OVERVIEW

The TU77 is a magnetic tape transport that records and
reads data in 9-track, non-return-to-zero (NRZI) or phaseencoded (PE) format. Bit density is 800 bits/in for the NRZI
format and 1600 bits/in for the PE format. The transport can
read data in either forward or reverse direction. The read/
write tape speed for both directions is 125 in/s. The nominal
rewind time for a 731.5 m (2400 ft) reel is 65 s.
The TU77 interfaces with the system processor via the
MASSBUS, a MASSBUS controller, and a TMO03 tape formatter. Up to four TU77s can be driven from one TMO3.
Figure 1-1 shows the basic system configuration for a
TU77. The TMO03 and its power supply (H740-DA) are
housed in the TU77 cabinet (H9602-KA corporate cabinet).
A TU77 containing a TMO3 is a master unit. A TU77 without the TMO3 is a slave unit.

CPU

MASSBUS*

CONTROLLER

MASSBUS.

TO 1-7

i i

OTHER

D TMO3

FORMATTERS

TM 1
|

|77077 MASTER TRANSPORT .

(TMO3/TAPE TRANSPORT)

‘T—‘X‘gg

TAPE

TRANSPORT

FORMATTER

L IRy T CIERERIEES CERTRINDS L]

S Lo L

EERRIEY CEER J

TO 1-3

OTHER
TRANSPORTS

* 1, PDP-11 & rh RH11

2. DECsystem 20 (KL10 & RH20)

3. VAX SYSTEMS
MA-2651

Figure 1-1

Basic System Configuration

INTRODUCTION

1.2

CONTROLS AND INDICATORS

Two groups of controls and indicators are in the TU77 cabinet. One group is the operator control panel; the other is the

TU77 maintenance controls and indicators.
1.2.1

Operator Control Panel

All operator controls and indicators on the TU77 control
panel are shown in Figure 1-2. Table 1-1 lists each control
and its function. Table

function.

1-2 lists each indicator and its

AUTO

+~— BACKWRAP

DEFEAT

MAN

SEE NOTE

—

power O

bot O
LOAD/REW

on fine O
ON LINE

file protect O
UNLOAD

Joad fault o

RESET

1600 O

TU77
/

NOTE:
SLAVE SELECT SWITCH NOT LABELED ON

PANEL.

Figure 1-2

TU77 Control Panel

Ma.2662

INTRODUCTION

Table 1-1

TU77 Operator Panel Controls

Control

Function

Slave select switch

Selects address (slave O to 3) of tape transport.

(unlabeled)

Each slave displays a unique number.

LOAD/REW

Pressing and releasing LOAD/REW initiates
one of three sequences.

With no tape in path, it starts a load

With tape in path but not tensioned, it
starts a midreel load sequence. In a midreel

sequence.

load sequence, tape loads and runs in
reverse to beginning-of-tape (BOT).
3.

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

ON LINE

Pressing and releasing ON LINE changes
transport from off-line to on-line. Pressing and

releasing it again changes transport from online to off-line.
UNLOAD

If TU77 is off-line, pressing and releasing
UNLOAD causes tape to rewind and unload.

If tape is already at BOT, it will unload. If
TU77 is on-line, UNLOAD has no effect.
RESET

Pressing and releasing RESET terminates all
off-line functions and clears a load fault.

BACKWRAP

AUTO (automatic) position allows a back-

DEFEAT

wrap and retry for 10-1/2 in. reel, with or
without a cartridge. MAN (manual) position

inhibits a backwrap and retry for 10-1/2 in,
reel, without a cartridge and small reels.

INTRODUCTION

Table 1-2

TU77 Operator Panel Indicators

Indicator

Function

power

Indicates presence of dc and secondary ac power.

bot

Indicates tape is at BOT.

on-line

Indicates TU77 is on-line. Transport reverts to offline mode if any of the following events occur.

ON LINE button is pressed.

An external rewind unload command is received.

Vacuum column interlock is broken.

AC power is lost.

RESET button is pressed.

file protect

Indicates that a reel of tape without a write-enable ring

load fault

Indicator flashes when a load fault occurs. For

has been loaded onto the transport.

example, it happens
1.

when an autoload sequence fails to load a tape

from a267 mm(10-1/2 in) reel after two attempts.
when an load sequence fails to load tape from a

216 or 178 mm (8-1/2 or7 in) reel after only one
attempt.

when a load sequence fails to load tape from a 267

mm (10-1/2 in) reel upon manual load after only
one attempt.

800

Indicates transport is set to read or write at 800 bits/in
(NRZI mode).

1600

Indicates transport is set to read or write at 1600

bits/in (PE mode).

INTRODUCTION

1.2.2 Maintenance Switch and Indicator Functions
Three printed circuit board assemblies (PCBAS) in the card
cage behind the base assembly contain all switches and indicators for maintenance. Figure 1-3 shows where these
switches and indicators (light emitting diodes or LEDs) are
located. Table 1-3 lists each indicator function on the
M8940 MTA PCBA. Table 1-4 lists each switch function

on the M8940 MTA PCBA. Table 1-5 lists the functions of
both S1 switches, S1/S2 on the control PCBA and S1 on the
reel servo PCBA.

ggp|||||||||||||||

SELECT7/

+5 VOLTS
W

CONTROL

MTA

TEST MODE

HRESHOL

BE DI 500,

277

L o
s

S' [

M2
4

Z
REEL

SERVO

MA-0164-83

Figure 1-3

Maintenance Controls and Indicators

Table 1-3

M8940 MTA Indicators

D Number

Function

Test mode

+5 V on

Unit select

INTRODUCTION

Table 1-4

M8940 MTA Switches
Function

Switch

Left

Right

1600 FCI*

3200 FCI*

NRZI

Forward

Write

Run continuous

Start/stop

Normal

Run

Test

‘

Reverse

’

" Stop

Read

* Phase-encoded write only.
If NRZI, all 1s only.

Table 1-5

Control and Reel Servo Switches
Function

Switch

Front

Control S1/S2

Reel servo S1

Center

Rear

Forward

Stop

Reverse

Servo

—

enable

Servo
disable

1.3 RELATED DOCUMENTS
Table 1-6 lists and describes documents related to the TU77
subsystem.

INTRODUCTION

Table 1-6