AT&T 6300 User manual

.......

*** WARNING ***
This equipment has been certified to comply with the limits for a
Class B computing device,
pursuant to Subpart J of Part 15 of FCC
Rules. Only peripherals (computer
input/output devices,
terminals,
printers, etc.) certified to comply with the Class B limits
may be attached to this computer. Operation with noncertified
peripherals is likely to
result in interference to radio and TV
reception.

Service Manual
CONTENTS
INTRODUCTION
GENERAL 1-3
ORGANIZATION 1-4
TOOLS AND ACCESSORIES. . . . . . . . . . . . . . . . . . 1-5
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
DISPLA Y 2-52
Monochrome Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-52
Color Display (Optional) 2-54
KEYBOARD 2-56
DISPLA Y AND KEYBOARD EXTENSION
CABLES 2-58
MINIMUM SYSTEM
CONFIGURATION 2-59
EXPANDED SYSTEM
CONFIGURATION 2-60
INST ALLATIONS
SITE PREPARATION......................... 3-3
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Service Manual
ENVIRONMENTAL
REQUIREMENTS 3-5
PHYSICAL CHARACTERISTICS. . . . . . . . . .. . . 3-6
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 ............................ 3-90
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
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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
Installing the Mouse Software With the Dual Diskette
Computer 3-107
Installing Mouse Software With the Hard Disk
Computer
... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-109
SYSTEM INSTALLATION. . . . . . . . . . . . . . . . . . . . 3-110
APPLYING POWER TO THE
SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-115
DIAGNOSTICS
INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
RESIDENT DIAGNOSTICS. . . . . . . . . . . . . . . . . . . 4-7
Operating Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
Test Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
Error Messages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
CUSTOMER TEST
DIAGNOSTICS 4-20
Loading Customer
Test 4-21
Operating Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22
Automatic Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-23
Manual Mode 4-25
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Service Manual
Test Descriptions. ................................. 4-32
Motherboard Test ............................... 4-32
Memory
Test. .................................. 4-33
Keyboard Test. ................................. 4-34
Video
System Test 4-35
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
Parallel Printer Test. ............................ 4-39
8087 Math Co-Processor 4-41
Mouse
Test .................................... 4-41
8530 Test. ..................................... 4-42
Video Option Board Test (DEB [Display Enhancement
Board]) ....................................... 4-42
2nd
HDU Drive and Controller Test ................. 4-45
SYSTEM TEST DIAGNOSTICS. .............. 4-47
Loading System Test ............................... 4-47
Operating Procedures. .............................. 4-48
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
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Service Manual
SYSTEM TEST DIAGNOSTICS (OVERLAY
VERSION) 4-87
Loading
System Test (Overlay Version) ................. 4-87
STAND-ALONE MOTHERBOARD DMA
TEST DIAGNOSTICS 4-89
DMA
Test 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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Service Manual
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
5 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
vii

Service Manual
Problems That May Occur in a One/Two Hard Disk
Configuration. .................................... 5-39
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
TROUBLESHOOTING WITH SYSTEM
TEST........................................... 5-54
Motherboard 5-55
Random Access Memory
(RAM). ...................... 5-59
Determining Faulty RAM Chips. . . . . . . . . . . . . . . . . . . . 5-65
Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-69
Video
System. .................................... 5-73
Parallel Port 5-88
Serial Port Test (Using 8250) ......................... 5-91
Mini-Floppy Disk
Drive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-94
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 (Display
Enhancement
Board) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-121
Video Option Board
Test . . . . . . . . . . . . . . . . . . . . . . . . 5-125
Second
Hard Disk Unit 5-135
viii

Service Manual
STAND-ALONE MOTHERBOARD DMA
TEST DIAGNOSTICS 5-142
Test Description. .................................. 5-142
Loading DMA Test. ................................ 5-142
Operating Procedures ............................ 5-143
POWER SUPPLY
ADJUSTMENT ................................ 5-145
REPLACING FAULTY
MODULES. .................................... 5-148
Removing
Upper Systenl 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
ix

Service Manual
APPENDIX A: SWITCHES
AND JUMPERS
INTRODUCTION. ............................. A-3
Switches A-3
Jumpers. ........................................ A-6
MOTHERBOARD.............................. A-7
Jumpers. ........................................ A-7
DIP Switch Setting A-9
DIPSW-O
Settings. ................................ A-IO
DIPSW-I Settings. ................................ A-13
HARD DISK CONTROLLERS. ................ A-16
HDUs Supported .................................. A-29
DISPLA Y CONTROLLER
BOARD........................................ A-30
Display Controller
Jumpers. ......................... A-30
Video Disable
Option. .............................. A-32
P4 Display Controller
Board. ...................... A-32
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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Service Manual
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
xi

INTRODUCTION
GENERAL..................................... 1-3
ORGANIZATION 1-4
TOOLS AND ACCESSORIES. ................. 1-5
1-1

INTRODUCTION
GENERAL
The purpose of this Service Manual is to support service personnel
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.
1-3

INTRODUCTION
ORGANIZATION
The information in this manual is organized as follows:
•
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.
•
Chapter 3, "INSTALLATIONS," discusses site preparation,
environmental requirements,
and installation of the PC 6300
and its supported options.
•
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.
•
Chapter 5, "MAINTENANCE," discusses troubleshooting
procedures for
the PC 6300 and contains procedures for the
replacement of faulty modules.
• 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.
• Appendix B, "FIELD REPLACEABLE MODULES," contains
a
list of the field replaceable modules and the information
required for ordering these modules.
1-4

INTRODUCTION
TOOLS AND ACCESSORIES
The following tools and accessories should be readily available
when performing maintenance on the PC 6300:
• Volt/Ohm Meter (VOM)
• Medium-Sized
Standard Screwdriver
• Chip
Insertion Tool
• Chip
Extraction Tool
•
Wrist Strap (Static Discharge Strap)
• 2 Blank Formatted (Scratch) Diskettes (Double-sided,
double-density, soft-sectored, 5-1/4 inch floppy
diskettes)
• Serial Loopback Connector (for testing Serial Port)
1-5

INTRODUCTION
• Parallel Loopback Connector (for testing Parallel Port)
• 1/4 inch Nutdriver
• 7/32 inch Nutdriver
• 3/16 inch Nutdriver
• 5/32 inch Nutdriver
• Phillips Screwdriver.
1-6

2
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
Memory Expansion Board (Optional) . . . . . . . . . . . . . . . . .
.. .2-42
Power Supply 2-44
DISPLAY ENHANCEMENT BOARD
(OPTIONAL). . . .. .. . . . . . . . .. . . . .. . . . .. .. . .. . . . . 2-49
SMALL EXPANSION BOX
(OPTIONAL).. .. . . . .. .. . . . . .. . .. . .. . . .. . .. . . . . . 2-51
DISPLA Y 2-52
Monochrome Display ............................... 2-52
Color Display (Optional) 2-54
2-1

SYSTEM OVERVIEW
KEYBOARD 2-56
DISPLAY AND KEYBOARD EXTENSION
CABLES 2-58
MINIMUM SYSTEM
CONFIGURATION 2-59
EXPANDED SYSTEM
CONFIGURATION............................ 2-60
2-2