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
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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
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