AT&T PC 6300 User manual

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PERSONAL COMPUTERS
PC 6300
T231
Service Manual
AT&T
Information Systems
SERVICES DIVISION EDUCATION
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Service Manual
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CONTENTS
INTRODUCTION
GENERAL 1-3
ORGANIZATION .. 1-1
TOOLS AND ACCESSORIES 15
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SYSTEM OVERVIEW
INTRODUCTION .. . 2 3
SYSTEM MODULE . . . . . . . 2 5
Motherboard 2-9
CPU and DMA Circuitry 2-15
Memory. 2-16
Input/Output Peripheral Interfaces 2-18
Input/Output Connectors . . ... . . .,. . . . . . ... . . . ... . 2-22
Motherboard Component Layout 2-25
Display Controllers 2-27
Bus Converter 2-31
Input/Output (I/O) Expansion Bus
Characteristics 2-33
Mini-Floppy Disk Unit(s) 2-35
Slim Hard Disk Units (Optional) 2-37
Hard Disk Unit Controllers (Optional) 2-39

Service Manual
Memory Expansion Board (Optional) ... ^ 2-42
Power Supply 2-44
DISPLAY ENHANCEMENT BOARD
(OPTIONAL) 2-49
SMALL EXPANSION BOX
(OPTIONAL). , 2-51
DISPLAY 2-52
Monochrome Display 2-52
Color Display (Optional) 2-54
KEYBOARD 2-56
DISPLAY AND KEYBOARD EXTENSION
CABLES 2-58
MINIMUM SYSTEM
CONFIGURATION 2-59
EXPANDED SYSTEM
CONFIGURATION 2-60
■■S 0f,
-C INSTALLATIONS
SITE PREPARATION 3-3
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ENVIRONMENTAL
REQUIREMENTS 3-5
PHYSICAL CHARACTERISTICS 3 (5
UNPACKING 3-7
OPTION INSTALLATION 3-8
Removing System Module Covers 3-9
Removing Upper Cover 3-10
Removing Lower Cover 3-11
Upgrading Motherboard Memory to 256KB or
640KB 3-12
Installing Memory Expansion Board 3-21
Upgrading Memory Expansion Board Memory to
384KB 3-27
Installing 8087 Numeric Data Processor 3-36
Replacing Mini-Floppy Disk Unit With Hard Disk
Unit .' 3-42
Removing Upper MFD Unit 3-42
Installing 10- or 20-MB Hard Disk Units 3-46
Installing Hard Disk Controller Board 3-48
Setting DIP Switches and Jumpers 3-52
Installing Small Expansion Box 3-63
Installing the Display Enhancement Board 3-77
Installing DEB Software • • • • -^-90
Floppy Disk Systems 3-91
Hard Disk Systems 3-94
Troubleshooting the DEB Installation . 3-97
Installing the Mouse 3-100
Installing the Ball in the Mouse 3-100
Connecting the Mouse to the Computer 3-102

Service Manual
Installing the Keyboard ROM 3-104
Opening the Keyboard 3-104
Removing Existing ROM Chip . 3-105
Installing New ROM Chip 3-105
Installing the Mouse Software 3-107 stalling tne mouse ooitware o-aui
S YSTEM INSTALLATION 3-110
APPLYING POWER TO THE
SYSTEM 3-115
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DIAGNOSTICS
INTRODUCTION .. . 4-5
RESIDENT DIAGNOSTICS 4-7
• Operating Procedures 4-8
Test Descriptions 4-10
Error Messages — • 4-15
Operating Procedures 4-22
Automatic Mode 4-23
Manual Mode 4-25
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Installing the Mouse Software With the Dual Diskette [ ;
Computer 3-107
Installing Mouse Software With the Hard Disk
Computer 3-109
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CUSTOMER TEST
DIAGNOSTICS 4-20
Loading Customer Test 4-21 j i
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Test Descriptions . . . . . ..... .. s w. . ... . . .. 4-.32
Motherboard Test 4-32
Memory Test 4-33
Keyboard Test . 4-34
^ Video System Test 4-3.5
Parallel Port Test . .: 4-36
' ' Serial Port(s) Test 4-37
48 TPI Floppy Disk Test 4-37
^ HDU Drive and Controller Test 4-38
I Parallel Printer Test 4-39
8087 Math Co-Processor 4^41
Mouse Test 4-41
8530 Test 4-42
I ( Video Option Board Test (DEB [Display Enhancement
Board]) 4-42
A 2nd HDU Drive and Controller Test 4-45
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' > SYSTEM TEST DIAGNOSTICS 4-47
W Loading System Test 4-47
1 Operating Procedures 4-48
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Test Descriptions 4-58
Motherboard Test 4-58
Memory Test. .. ...... .... 4-60
Keyboard Test .. .• 4-62
Video System Test 4-63
Parallel Port Test 4-67
Serial Port(s) Test (Using 8250) 4-69
48 TPI Floppy Disk Test 4-71
MB HDU Drive and Controller Test 4-74
8087 Math Co-Processor 4-77
Parallel Printer Test 4-77
Mouse Test . 4-79
8530 Test 4-80
Video Option Board Test [Display Enhancement Board
(DEB)] 4-80
2nd HDU Drive and Controller Test 4-83

Service Manual
SYSTEM TEST DIAGNOSTICS (OVERLAY
VERSION) 4-87
Loading System Test (Overlay Version) 4-87
STAND-ALONE MOTHERBOARD DMA
TEST DIAGNOSTICS 4-89
DMATest . . .i . 4-89
STAND-ALONE LOW-LEVEL FORMAT
UTILITY TEST 4-92
General Characteristics 4-93
The Bad Track Table 4-95
List of Operations 4-96
Help 4-101
HDU Configuration 4-102
Low-Level Format .. ... 4-105
Display and Edit Bad Track Table 4-110
Format Bad Tracks 4-119
Verify Surface Test 4-121
Ship the Unit 4-124
Exit Low-Level Format (LLF) Utility 4-125
CUSTOMER AND SYSTEM TEST ERROR
MESSAGES 4-127
100—Motherboard Tests 4-127
300—Memory Tests 4-129
400—Keyboard Tests 4-133
500—Video Tests 4-137
600—Parallel Port Tests • • • 4-144
700—8250 Serial Port Tests — .. 4-145
800-MFD Unit Tests 4-147
900-HDU Tests 4-149
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lOXX—Parallel Printer Tests 4-152
18XX—8087-2 Numeric Co-Processor Tests 4-152
20XX—Mouse Tests 4-153
21XX—8530 Serial Port Tests 4-154
23XX—Video Option Board (DEB) Tests 4-155
24XX—HDU Drive No. 2 Tests 4-167
MAINTENANCE
GENERAL 5.5
Troubleshooting 5.5
Replacing Faulty Modules 5-5
Reminders 5.6
TROUBLESHOOTING WITHOUT SYSTEM
TEST 5.7
System Will Not Power Up Normally '.. 5-7
System Load Check on Power Supply 5-9
Short Isolation Procedure 5-19
Display Check 5-26
Mini-Floppy Disk Unit Check 5-28
Two Mini-Floppy Disk Units 5-28
One MFD Unit and One HDU 5-33
System Will Not Access Hard Disk 5-36
Hard Disk Problems 5-38

Service Manual
Problems That May Occur in a One/Two Hard Disk
Configuration 5-39
Hard Disk Unit 5-99
Parallel Printer Test ^ . 5-105
8087-2 Math Co-Processor — ... 5-109
Mouse 5-112
Mouse Test 5-114
8530 Serial Port Test 5-118
Video Option Board Test 5-125
Second Hard Disk Unit 5-135
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Placing Low-Level Format and Bad Track Mapping on the
Hard Disk • 5-41
Partition Hard Disk for MS-DOS 5-45
Formatting the Hard Disk 5-47
Hard Disk Unit "Not Ready" on Cold Start 5-50
Resident Diagnostic Error Messages 5-51 ^
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TROUBLESHOOTING WITH SYSTEM
test •• ••• 5-54
Motherboard 5-55
Random Access Memory (RAM) 5- •
Determining Faulty RAM Chips 5-
Keyboard S-Oi'
Video System — ..... 5-73
Parallel Port 5-88
Serial Port Test (Using 8250) 5-91
Mini-Floppy Disk Drive 5-94 pj
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Video Option Board (Display Enhancement ^
Board) 5-121 ^
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STAND-ALONE MOTHERBOARD DMA ^
TEST DIAGNOSTICS 5 i42
Test Description . . . . ..... .. . . .> .. 5-142
Loading DMA Test 5-142
Operating Procedures 5-143
^ POWER SUPPLY
j [ ADJUSTMENT 5-145
_ REPLACING FAULTY
n MODULES 5-148
Removing Upper System Module Cover ; . . 5-149
Removing Lower System Module Cover ; 5-150
Replacing Power Supply Unit. .. .' 5-151
Replacing Fan ..; 5-156
Replacing Motherboard 5-157
Replacing Bus Converter .... .. 5-161
Replacing Display Controller 5-162
Replacing Lower Mini-Floppy Disk Unit 5-168
Replacing Upper Mini-Floppy Disk Unit ....... .... .. ... 5-175
Replacing Slim HDU 5-180
Replacing Memory Expansion Board 5-186
Replacing HDU Controller . .. .. 5-187
Replacing Small Expansion Box (External
HDU) 5-189
Replacing Memory Chips 5-193
Mouse Care and Cleaning 5-198
Cleaning Keyboard Contacts 5-201
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APPENDIX A: SWITCHES
AND JUMPERS f]
INTRODUCTION A-3
Switches
Jumpers • •
MOTHERBOARD • -
Jumpers A-7
DIP Switch Setting A-9
DIPSW-0 Settings • A.-10
DIPSW-1 Settings . •. A-13
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HARD DISK CONTROLLERS. A-16
HDUs Supported ^"29
DISPLAY CONTROLLER ^
BOARD ^-30 "
Display Controller Jumpers A-30
Video Disable Option A-32 «
P4 Display Controller Board A'-32 J j
P8 Display Controller Board A-34
Display Enhancement Board Jumpers A-35 ^
Mini-Floppy Disk Units A-38 _
Jumpers A-38
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Resistor Pack or Terminating Resistor A-39
Toshiba Mini-Floppy Disk Unit A-39
OPE Mini-Floppy Disk Unit A-41
Matsushita Mini-Floppy Disk Unit A-43
HARD DISK UNIT A 45
Jumper and Switch Setting A-45
AT&T PC 6300 ACCEPTANCE
PROCEDURE A 54
APPENDIX B: FIELD
REPLACEABLE MODULES
FIELD REPLACEABLE
MODULES B-3
INDEX

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' INTRODUCTION
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INTRODUCTION
GENERAL i-.s
ORGANIZATION 1-4
TOOLS AND ACCESSORIES 1-5
1-1

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INTRODUCTION
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GENERAL
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1 I '
The purpose of this Service Manual is to support service personnel
n in the installation and maintenance of the AT&T Personal
Computer 6300 (PC 6300) and its options. Since there is a
minimum number of moving parts in the system, there is virtually
^ no preventive maintenance. Therefore, the maintenance of the
| | system is limited to signal adjustments and troubleshooting. The
' ' only signal adjustment is on the power supply.
All Diagnostic Tests and Maintenance Procedures are designed for
AT&T Products only.
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1-3

INTRODUCTION
The information in this manual is organized as follows:
Chapter 4, "DIAGNOSTICS," contains procedures for
performing all three levels of diagnostics on the PC 6300. It
also contains a description of the test performed during the
diagnostics and error messages.
Appendix A, "DIP SWITCHES AND JUMPERS," discusses
the location and purpose of the Dual In-Line Package (DIP)
Switches and Jumpers that are contained in the PC 6300.
1-4
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ORGANIZATION ^
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Chapter 2, "SYSTEM OVERVIEW," contains an overview of
the PC 6300 and its main units. It also contains some
detailed information on the operation and functions of the
system modules. 1 j
Chapter 3, "INSTALLATIONS," discusses site preparation, ^
environmental requirements, and installation of the PC 6300 ]
and its supported options. -'
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• Chapter 5, "MAINTENANCE," discusses troubleshooting ^
procedures for the PC 6300 and contains procedures for the j )
replacement of faulty modules. —■
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• Appendix B, "FIELD REPLACEABLE MODULES," contains
a list of the field replaceable modules and the information
required for ordering these modules. j j
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