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L Q - 2 5 5 0
TECHNICAL MANUAL




EPSON
REV.-A

PRECAUTIONS
Precautionary notations throughout the text are categorized relative to 1) personal injury, and 2) damage
to equipment:
DANGER Signals a precaution which, if ignored, could result in serious or fatal personal
injury. Great caution should be exercised in performing procedures preceded by
a DANGER headings.
WARNING Signals a precaution which, if ignored, could result in damage to equipment.
The precautionary measures itemized below should always be observed when performing repair/main-
tenance procedures.

DANGER
1. ALWAYS DISCONNECT THE PRODUCT FROM BOTH THE POWER SOURCE AND THE
HOST COMPUTER BEFORE PERFORMING ANY MAINTENANCE OR REPAIR
PROCEDURE.
2. NO WORK SHOULD BE PERFORMED ON THE UNIT BY PERSONS UNFAMILIAR WITH
BASIC SAFETY MEASURES AS DICTATED FOR ALL ELECTRONICS TECHNICIANS IN
THEIR LINE OF WORK.
3. WHEN PERFORMiNG TESTING AS DICTATED WITHIN THIS MANUAL, DO NOT
CONNECT THE UNIT TO A POWER SOURCE UNTIL INSTRUCTED TO DO SO. WHEN
THE POWER SUPPLY CABLE MUST BE CONNECTED, USE EXTREME CAUTION IN
WORKING ON POWER SUPPLY AND OTHER ELECTRONIC COMPONENTS.


WARNING
1. REPAIRS ON EPSON PRODUCT SHOULD BE PERFORMED ONLY BY AN EPSON
CERTIFIED REPAIR TECHNICIAN.
2. MAKE CERTAIN THAT THE SOURCE VOLTAGE IS THE SAME AS THE RATED
VOLTAGE, LISTED ON THE SERIAL NUMBER/RATING PLATE. IF THE EPSON PROD-
UCT HAS A PRIMARY-AC RATING DIFFERENT FROM THE AVAILABLE POWER
SOURCE, DO NOT CONNECT IT TO THE POWER SOURCE.
3. ALWAYS VERIFY THAT THE EPSON PRODUCT HAS BEEN DISCONNECTED FROM THE
POWER SOURCE BEFORE REMOVING OR REPLACING PRINTED CIRCUIT BOARDS
AND/OR INDIVIDUAL CHIPS.
4. IN ORDER TO PROTECT SENSITIVE KP CHIPS AND CIRCUITRY, USE STATIC
DISCHARGE EQUIPMENT, SUCH AS ANTI-STATIC WRIST STRAPS, WHEN ACCESS-
ING INTERNAL COMPONENTS.
5. REPLACE MALFUNCTIONING COMPONENTS ONLY WITH THOSE COMPONENTS
RECOMMENDED BY THE MANUFACTURER; INTRODUCTION OF SECOND-SOURCE
ICS OR OTHER NONAPPROVED COMPONENTS MAY DAMAGE THE PRODUCT AND
VOID ANY APPLICABLE EPSON WARRANTY.




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PREFACE
This manual describes functions, theory of electrical and mechanical
operations, maintenance, and repair of the LQ-2550.
The instructions and procedures included herein are intended for the
experienced repair technician, and attention should be given to the
precautions on the preceding page. The chapters are organized as follows:


Chapter 1 - Provides a general product overview, lists specifications,
and illustrates the main components of the printer.


Chapter 2 - Describes the theory of printer operation.


Chapter 3 - Discusses the options


Chapter 4 - Includes a step-by-step guide for product disassembly,
assembly, and adjustment.


Chapter 5 - Provides Epson-approved techniques for troubleshooting.


Chapter 6 - Describes preventive maintenance techniques and lists
lubricants and adhesives required to service the equipment.



" The contents of this manual are subject to change without notice.




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REVISION TABLE
f'!
.
REVISION DATE ISSUED CHANGE DOCUMENT

A March 31, 1988 I 1st issue




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TABLE OF CONTENTS
CHAPTER 1. GENERAL DESCRIPTION
CHAPTER 2. OPERATING PRINCIPLES
CHAPTER 3. OPTIONAL EQUIPMENTS
CHAPTER 4. DISASSEMBLY, ASSEMBLY, AND ADJUSTMENT
CHAPTER 5. TROUBLESHOOTING
CHAPTER 6. MAINTENANCE
APPENDIX