Compaq Deskpro 386 - Desktop PC Manual

COMPAQ DESKPRO 386
Personal Computer
MAINTENANCE AND
SERVICE GUIDE

NOTICE
The information in this guide is subject to change without notice.
COMPAQ COMPUTER CORPORATION SHALL NOT BE LIABLE FOR TECH-
NICAL OR EDITORIAL ERRORS OR OMISSIONS CONTAINED HEREIN; NOR
FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES RESULTING FROM
THE FURNISHING, PERFORMANCE, OR USE OF THIS MATERIAL.
This guide contains information protected by copyright. No part of this guide
may be photocopied or reproduced in any form without prior written consent
from Compaq Computer Corporation.
© Copyright 1988 by Compaq Computer Corporation.
All rights reserved. Printed in the U.S.A.
COMPAQ®, COMPAQ DESKPRO®, COMPAQ DESKPRO 286®, COMPAQ PORTABLE II®,
COMPAQ DESKPRO 386®, COMPAQ PORTABLE III®, COMPAQ DESKPRO 386/20®,
COMPAQ PORTABLE 386®, COMPAQ DESKPRO 386s®, COMPAQ DESKPRO 386/25,
COMPAQ DESKPRO 386/20e, and COMPAQ SLT/286 are trademarks of
Compaq Computer Corporation.
The software described in this guide is furnished under a license agreement
of nondisclosure. The software may be used or copied only in accordance with
the terms of the agreement.
Microsoft®, MS®, and MS-DOS®are trademarks of Microsoft Corporation.
MS®OS/2 is a product of Microsoft Corporation.
Product names mentioned herein are used for identification purposes only and
may be trademarks and/or registered trademarks of their respective companies.
MAINTENANCE AND SERVICE GUIDE
COMPAQ DESKPRO 386 Personal Computer
Third Edition (February 1988)
Second Edition (June 1987)
First Edition (August 1986)
Assembly Number 108033-003
Text Number 108035-003
Addendum 108431-001 (November 1988)
Compaq Computer Corporation
®Registered United States Patent and Trademark Office.

ii
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.
WARNING
This equipment generates, uses, and can radiate radio frequency
energy. If not installed and used in accordance with the manufactur-
er’s instructions, if may cause interference with radio and television
reception. 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, which are designed to provide reasonable protection
against such interference. If this occurs, the user will be required
to take whatever measures may be necessary to eliminate the interfer-
ence. In attempting to do so, the user should:
□Reorient the receiving antenna.
□Relocate the computer with respect to the receiver with which it
interferes..
□Plug the computer into a different AC receptacle so that the com-
puter and the receiver with which it interferes are on different
branch circuits.
If necessary, consult an Authorized COMPAQ Computer Dealer or an
experienced radio/television technician for additional suggestions.

iii
NOTICE
Compaq Computer Corporation requires that all peripheral devices be connected
to this computer via shielded cables with metal RFI/EMI connector hoods.
WIRE TYPE: Multipaired overall-shielded; Belden #98XX; Alpha #54XX;
or equivalent.
CONNECTOR
HOOD: RFI/EMI metal shield; AMP #74517X-X; or equivalent.
It is important that the chassis ground of any peripheral device be connected
to the computer chassis. An Alpha #1221 flat-braided strap is sufficient. This
strap is not necessary if the shielded cable connects the two chassis.

iv
PREFACE
The COMPAQ DESKPRO 386 PERSONAL COMPUTER MAINTENANCE
AND SERVICE GUIDE is a troubleshooting, maintenance, and repair guide
that can be used as a reference when servicing the COMPAQ DESKPRO 386
Personal Computer.
All troubleshooting and repair procedures are detailed to allow subassem-
bly/module-level repair only.
CAUTION
Because of the complexity of the individual boards and subassemblies,
Compaq Computer Corporation strongly recommends that you do not
attempt to make field repairs at the component level.

v
SUMMARY OF TEXT
The COMPAQ DESKPRO 386 MAINTENANCE AND SERVICE GUIDE con-
tains the following eight chapters:
Chapter 1 OPERATING AND PERFORMANCE SPECIFICATIONS pro-
vides operating and performance specifications for the COMPAQ
DESKPRO 386 Personal Computer.
Chapter 2 POWER-ON SELF-TEST (POST)/PROBLEM ISOLATION describes
the internal system diagnostics programs that run automati-
cally when you turn on the system. A flowchart is provided for
identifying and correcting problems that can occur during the
Power-On Self-Test procedure.
Chapter 3 SETUP PROGRAM describes the purpose and function of the
SETUP program, including explanations about when you must
run the SETUP program and when the system prompts you to
run the SETUP program.
Chapter 4 ADVANCED DIAGNOSTICS PROGRAM describes the use and
function of the COMPAQ ADVANCED DIAGNOSTICS program
and provides a detailed description of the various diagnostics
routines.
Chapter 5 ERRORMESSAGESANDCODESlistsanddescribesthePower-
On Self-Test (POST) and the ADVANCED DIAGNOSTICS pro-
gram error messages and codes. This chapter also identifies
the action required to resolve each problem described by the
corresponding error message or code.

vi
Chapter 6 ILLUSTRATED PARTS CATALOG contains illustrated part
breakdowns, order numbers, and part names for the COMPAQ
DESKPRO 386 Personal Computer.
Chapter 7 REMOVAL AND REPLACEMENT PROCEDURES describes
how to remove and replace subassemblies for the COMPAQ
DESKPRO 386 Personal Computer.
Chapter 8 JUMPER SETTINGS AND SWITCH SETTINGS provides de-
tailed information for setting jumpers and switches on the
COMPAQ DESKPRO 386 Personal Computer.

vii
REQUIRED TOOLS AND SUPPLIES
To service the COMPAQ DESKPRO 386 Personal Computer, you need:
□Torx T-10 screwdriver
□Torx T-15 screwdriver
□Small Phillips screwdriver
□COMPAQ Personal Computer ADVANCED DIAGNOSTICS Diskette
Version 5.XX (part no. 108137)
□Formatted scratch diskette(s)
□25-pin printer loopback plug (part no. 100755-001)
□9-pin serial loopback plug (part no. 102999-001)
□80387 coprocessor removal tool (part no. 108492-001)
Optional tools are:
□ Memory chip insertion tool
□ Memory chip removal tool

viii
ADDITIONAL INFORMATION
The following documentation and related software are available to support
the COMPAQ DESKPRO 386 Personal Computer.
Associated Documentation:
□ COMPAQ DESKPRO 386 PERSONAL COMPUTER OPERATIONS
GUIDE
□ COMPAQ DESKPRO 386 TECHNICAL REFERENCE GUIDE
VOLUMES I and II
□ MS-DOS®/BASIC VERSION 3.1 REFERENCE GUIDE
□ MS-DOS®/BASIC VERSION 3.2 REFERENCE GUIDE
□ MS-DOS®/BASIC VERSION 3.3 REFERENCE GUIDE
□ Service Advisories
□ Service Bulletins
□ HOW TO DO BUSINESS WITH COMPAQ SERVICE
□ COMPAQ ENHANCED COLOR GRAPHICS BOARD OPERATIONS
AND INSTALLATION GUIDE
□ COMPAQ ENHANCED COLOR GRAPHICS BOARD TECHNICAL
REFERENCE GUIDE
□ COMPAQ VIDEO GRAPHICS CONTROLLER BOARD TECHNICAL
REFERENCE GUIDE
□ COMPAQ SERVICE QUICK REFERENCE GUIDE
□ SY-TOS TAPE OPERATING SYSTEM USER’S GUIDE

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CONTENTS
Chapter 1
OPERATING AND PERFORMANCE SPECIFICATIONS
1.1 INTRODUCTION 1-1
1.2 COMPAQ DESKPRO 386 PERSONAL COMPUTER
SYSTEM UNIT
1-2
1.3 COMPAQ ENHANCED KEYBOARD 1-3
1.4 COMPAQ 84-KEY KEYBOARD 1-3
1.5 COMPAQ DUAL-MODE MONITOR 1-4
1.6 COMPAQ COLOR MONITOR 1-5
1.7 COMPAQ VIDEO GRAPHICS COLOR MONITOR 1-6
1.8 COMPAQ VIDEO GRAPHICS
MONOCHROME MONITOR 1-8
1.9 360-KBYTE 5¼-INCH DISKETTE DRIVE 1-10
1.10 1.2-MEGABYTE 5¼-INCH DISKETTE DRIVE 1-12
1.11 1.44-MEGABYTE 3½-INCH DISKETTE DRIVE 1-12
1.12 40-MEGABYTE FIXED DISK DRIVE 1-13
1.13 70-MEGABYTE FIXED DISK DRIVE 1-14
1.14 130-MEGABYTE FIXED DISK DRIVE 1-15
1.15 40-MEGABYTE FIXED DISK DRIVE BACKUP (TAPE) 1-16
1.16 135-MEGABYTE FIXED DISK DRIVE BACKUP (TAPE) 1-17
1.17 300-/600-MEGABYTE FIXED DISK DRIVE
EXPANSION UNIT 1-18
1.18 300-MEGABYTE FIXED DISK DRIVE FOR THE
EXPANSION UNIT 1-19

x
Chapter 2
POWER-ON SELF-TEST (POST)/PROBLEM ISOLATION
2.1 INTRODUCTION 2-1
2.2 POWER-ON SELF-TEST (POST) 2-1
2.3 PRELIMINARY STEPS TO PROBLEM ISOLATION 2-2
2.4 PROBLEM ISOLATION FLOWCHART 2-2
Chapter 3
SETUP PROGRAM
3.1 WHEN TO RUN SETUP 3-1
3.2 HOW TO RUN SETUP 3-2
Chapter 4
ADVANCED DIAGNOSTICS PROGRAM
4.1 PRELIMINARY STEPS 4-1
4.2 MAIN MENU 4-2
4.3 ADVANCED DIAGNOSTICS PROGRAM 4-4
4.4 TEST SELECTION MENU 4-5
Chapter 5
ERROR MESSAGES AND CODES
5.1 INTRODUCTION 5-1
5.2 POWER-ON SELF TEST ERROR MESSAGES 5-1
5.3 ADVANCED DIAGNOSTICS ERROR CODES 5-4
5.4 MEMORY ERROR CODES 5-31
5.5 EXTDISK MESSAGES 5-36

xi
Chapter 6
ILLUSTRATED PARTS CATALOG
6.1 INTRODUCTION 6-1
6.2 SPARE PARTS LIST, U.S. 6-2
6.3 SPARE PARTS LIST, INTERNATIONAL 6-9
6.4 PARTS LIST 6-10
6.5 300-/600-MEGABYTE FIXED DISK EXPANSION
UNIT PARTS LIST 6-21
Chapter 7
REMOVAL AND REPLACEMENT PROCEDURES
7.1 INTRODUCTION 7-1
7.2 MONITOR 7-2
7.3 KEYBOARD 7-5
7.4 POWER FUSE 7-6
7.5 PRELIMINARY STEPS TO INTERNAL REMOVAL AND
REPLACEMENT PROCEDURES 7-8
7.6 SYSTEM UNIT COVER AND
INTERNAL CONFIGURATION 7-9
7.7 POWER SUPPLY 7-12
7.8 BATTERY 7-15
7.9 SECURITY LOCK 7-18
7.10 EXPANSION BOARD(S) 7-19
7.11 80287 COPROCESSOR 7-23
7.12 MEMORY EXPANSION BOARD(S) 7-24
7.13 MEMORY CHIP(S) 7-26
7.14 SPEAKER COMPONENT AND SECURITY
LOCK SWITCH 7-29

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7.15 MASS STORAGE DEVICE(S) 7-33
7.16 SYSTEM BOARD 7-39
7.17 INTEL 387 COPROCESSOR 7-45
7.18 LOST KEY 7-49
7.19 300-/600-MEGABYTE FIXED DISK DRIVE
EXPANSION UNIT 7-50
Chapter 8
JUMPER SETTINGS AND SWITCH SETTINGS
8.1 INTRODUCTION 8-1
8.2 SYSTEM BOARDS 8-2
8.3 32-BIT SYSTEM MEMORY BOARD 8-6
8.4 .5- TO 2-MEGABYTE 16-BIT MEMORY
EXPANSION BOARD 8-8
8.5 1- TO 2-MEGABYTE AND 4- TO 8-MEGABYTE 32-BIT
MEMORY EXPANSION BOARD 8-10
8.6 ESDI FIXED DISK DRIVE CONTROLLER BOARD 8-12
8.7 MULTIPURPOSE FIXED DISK DRIVE
CONTROLLER BOARDS 8-14
8.8 FIXED DISK DRIVE CONTROLLER BOARD 8-18
8.9 HOST ADAPTER BOARD 8-20
8.10 COMPAQ ENHANCED COLOR GRAPHICS BOARD 8-22
8.11 VIDEO DISPLAY CONTROLLER BOARD 8-28
8.12 COMPAQ VIDEO GRAPHICS CONTROLLER BOARD 8-31
8.13 ASYNCHRONOUS COMMUNICATIONS/PARALLEL
PRINTER BOARD 8-32
8.14 300-/600-MEGABYTE FIXED DISK DRIVE
EXPANSION UNIT 8-36

xiii
Chapter 9
MASS STORAGE CONFIGURATIONS
9.1 THEORY OF OPERATION 9-1
9.2 SYSTEM CONFIGURATION 9-2
9.3 SETTING UP THE EXTERNAL FIXED DISK DRIVE
EXPANSION UNIT 9-6
Appendix A
INDEX A-1

xv
FIGURES
5-1. Memory Error Locations on the 32-Bit
System Memory Board 5-31
5-2. Memory Error Locations on the 1- to 2-Megabyte
32-Bit Memory Board 5-32
5-3. Memory Error Locations on the 4- to 8-Megabyte
32-Bit Memory Board 5-33
6-1. System Unit (Exterior and Battery) 6-11
6-2. System Unit (Interior with Memory Options) 6-13
6-3. System Unit (Interior with Controller Boards
and Mass Storage Options) 6-15
6-4. COMPAQ Enhanced Keyboard 6-16
6-5. 84-Key Keyboard 6-17
6-6. COMPAQ Dual-Mode Monitor Assembly 6-18
6-7. COMPAQ Color Monitor 6-19
6-8. COMPAQ Video Graphics Color Monitor 6-20
6-9. COMPAQ Video Graphics Monochrome Monitor 6-21
7-1. COMPAQ Dual Mode Monitor (Installed) 7-2
7-2. COMPAQ Color Monitor (Installed) 7-3
7-3. COMPAQ Video Graphics Color Monitor (Installed) 7-3
7-4. COMPAQ Video Graphics Monochrome Monitor (Installed) 7-4
7-5. Removing the Keyboard 7-5
7-6. Removing the Fuse Holder 7-6
7-7. Replacing the Power Fuse 7-7
7-8. Location of the Three Screws on the Back
of the System Unit 7-9

xvi
7-9. Removing the System Unit Cover 7-10
7-10. Overhead View of the COMPAQ DESKPRO 386 Personal
Computer with the System Unit Cover Removed 7-11
7-11. Location of the Power Supply Assembly 7-12
7-12. Removing the Power Supply Screws 7-13
7-13. Removing the Power Supply Assembly 7-13
7-14. Location of the Power Supply Connector
on the System Board
7-14
7-15. Location of the Battery 7-16
7-16. Location of the Battery Connector 7-16
7-17. Removing the Battery 7-17
7-18. Removing the Security Lock (Interior View) 7-18
7-19. Location of the Reinforcement Bracket 7-19
7-20. Location of the RF Shield 7-20
7-21. Location of the Cable Cover 7-20
7-22. Removing the ESDI Fixed Disk Drive
Controller Board Signal Cables 7-21
7-23. Removing the Multipurpose Fixed Disk Drive
Controller Board Signal Cables 7-21
7-24. Removing the Fixed Disk Drive
Controller Board Signal Cables 7-22
7-25. Removing an Expansion Board 7-22
7-26. Location of the 80287 Coprocessor Socket on
the System Board 7-23
7-27. Removing the 32-Bit Memory Expansion Board
from the 32-Bit System Memory Board 7-25
7-28. Removing the Memory Chip 7-27
7-29. Inserting the Memory Chip 7-28

xvii
7-30. Location of the Speaker/Board Guide Assembly 7-30
7-31. Removing the Speaker/Board Guide Assembly 7-30
7-32. Location of the Speaker Connector and Security
Lock Switch Connector 7-31
7-33. Removing the Speaker Assembly 7-32
7-34. Removing the Security Lock Switch Assembly 7-32
7-35. Location Designators for COMPAQ DESKPRO 386
Mass Storage Devices 7-33
7-36. Location of the Cables for Mass Storage Devices
in Positions A and D 7-34
7-37. Location of the Screws for Positions A and D 7-35
7-38. Removing a Mass Storage Device from Position A 7-35
7-39. Removing a Mass Storage Device from Position D 7-35
7-40. Disconnecting Cables from Mass Storage Device B or C 7-37
7-41. Removing a Mass Storage Device from Position C 7-37
7-42. Location of the Power Cable Connectors, Battery
Connector, Monitor Power Connector, and Power Supply
Connector on the COMPAQ DESKPRO 386 System Board
Version 1 (assy. no. 000401) 7-40
7-43. Location of the Power Cable Connector, Battery
Connector, Monitor Power Connector, and Power Supply
Connector on the COMPAQ DESKPRO 386 System Board
Version 2 (assy. no. 000558) 7-41
7-44. Location of the Security Lock Switch Connector, Keyboard
Connector, and Speaker Connector on the COMPAQ
DESKPRO 386 System Board Version 1 (assy. no. 000401) 7-42
7-45. Location of the Security Lock Switch Connector, Keyboard
Connector, and Speaker Connector on the COMPAQ
DESKPRO 386 System Board Version 2 (assy. no. 000558) 7-43

xviii
7-46. Removing the System Board 7-44
7-47. Removing the 80387 Coprocessor 7-46
7-48. Aligning the 80387 Coprocessor 7-47
8-1. COMPAQ DESKPRO 386 Personal Computer System
Board Version 1 (assy. no. 000401) 8-2
8-2. COMPAQ DESKPRO 386 System Board Version 2
(assy. no. 000558) 8-4
8-3. 32-Bit System Memory Board (assy. no. 000413) 8-6
8-4. .5- to 2-Megabyte 16-Bit Memory Expansion Board
(assy. no. 000458) 8-8
8-5a. 1- to 2-Megabyte 32-Bit Memory Expansion Board
(assy. no. 000450) 8-10
8-5b. 4- to 8-Megabyte 32-Bit Memory Expansion Board
(assy. no. 000459) 8-10
8-6. Jumper 101 Setting on the 1- to 2-Megabyte
(assy. no. 000450) or 4- to 8-Megabyte (assy. no. 000459)
32-Bit Memory Expansion Board 8-11
8-7. ESDI Fixed Disk Drive Controller Board (assy. no.
WD1005WAH) 8-12
8-8. Multipurpose Fixed Disk Drive Controller Board
(assy. no. 000336-001 or -021) 8-14
8-9. Multipurpose Fixed Disk Drive Controller Board
(assy. no. 000519 and 000815) 8-16
8-10. Fixed Disk Drive Controller Board
(assy. no. WD1002WAH) 8-18
8-11. Host Adapter Board (assy. no. 000774) 8-20
8-12. COMPAQ Enhanced Color Graphics Boards
(assy. no. 000410 and 000471) 8-22
8-13. Setting for a COMPAQ Color or Compatible
Enhanced Color Monitor 8-27