Epson LQ-1500 User manual

LQ-1500
SERVICE MANUAL
EPSON
®
a9
Printed on Recycled Paper

TABLE OF CONTENTS
CHAPTER 1
GENERAL
1.1 Product Overview ................................................................................................................................
1-1
1.2 LQ-1500 Interface Overview ...............................................................................................................
1-1
1 .3 Specifications .....................................................................................................................................
1-1
1 .4 Major Components .............................................................................................................................. 1-4
CHAPTER 2
PRINCIPLES OF OPERATION
2.1 General..
..............................................................................................................................................
2-1
2.2 ConnectIon Diagram
...........................................................................................................................
2-1
2.3 Connector Pin Assignment ................................................................................................................. 2-3
2.3.1 Connector on UXMCL circuit board........................................................................................... 2-3
2.3.2 Connector on UXDRV circuit board.. ....................................................................................... 2-8
2.3.3 Connector on UXPS/PSU 24E circuit board.. ........................................................................... 2-12
2.4 Electrical Circuit .................................................................................................................. .............. 2-13
2.4.1 Power circuit................................................................................................................. .......... 2-13
2.4.2 Reset circuit ............................................................................................................................... 2-22
2.4.3 Sensor circuit.. ........................................................................................................................ 2-22
2.4.4 Carriage motor control circuit........................................................................ ................... ...... 2-26
2.4.5 LF motor control circuit ............................................................................................................. 2-34
2.4.6 Head driver circuit..................................................................................................................... 2-37
2.4.7 Auto sheet load circuit .............................................................................................................. 2-39
2.4.8 Other function........................................... .............................................................................. 2-40
2.5 Printer Mechanism............................................................................................................................... 2-41
2.5.1 Operation ................................................................................................................................ 2-41
CHAPTER 3
OPTIONAL EQUIPMENT
3.1 Centronics Compatible Parallel Interface........................................................................................... 3-1
3.1 .1
Introduction ............................................................................................................................. 3-1
3.1 .2 Specification.. ................................ .............................. ...................................................... 3-1
3.1 .3 Operating principal .................................................................................................................. 3-4
3.1.4 Block diagram.............................
.... ..............................
...
................................................ 3-6
3.1 .5 Circuit diagram .......
......... ............................. ......... .............................................................. 3-7
3.1 .6 Component layout ............... .................................................................................................. 3-8
3.2 RS-232C/Current Loop Interface..................................... ..............
.... .............................................. 3-9
3.2.1 lntroductron ............ .,.,., .......................................................................................................... 3-9
3.2.2 Specification.. ........
... ....... .................................... ..................................................... .......... 3-9
3.2.3 Operating principal ....................................... .................................................... ...................... 3-15
3.2.4 Block diagram....................................... ..... ............................................................................. 3-19
3.2.5 Circuit diagram.. ......................... .......... ..... ............................................... ........................ 3-20
3.2.6 Component layout .................................................................................................................... 3-21
3.3 IEEE-488 Interface.. ...................... ........ ........ ..... .......................................................................... 3-22
3.3.1 Introduction .......... ........ ............................................................. ..................................... 3-22
3.3.2 Specification.. ..... ......... .................................................................................................... 3-22
3.3.3 IEEE-488 operatronal parameters.............................
....
..... .................................................... 3-26
3.3.4 IEEE-488 functional commands ......................................... ........ ....................................... 3-27
3.3.5 Block diagram..... .............................. ................. ........ ....................................................... 3-29
3 3.6 Circuit diagram.. ................................... .......
....
... .................................................................. 3-31
3.3.7 Component layout ................................ .............................................................. .............. 3-32
3.4 Single Bin Cut Sheet Feeder (# 8334), Double Bin Cut Sheet Feeder (# 8344) ................................. 3-33
3.4.1 Introduction ......... ...........................
... .... ............................................................. ........... 3-33
3.4.2 Specifications.. ..... ........ .......... ...... ................................................. .......... .................. 3-34
3.4.3 Principle of operation.. ........... ...................................................................
.... ........................ 3-36
3.4.4 Disassembly and assembly.............................................................. ........................................ 3-42
3.4.5 Troubleshooting.. ......................................... ...................................................................... 3-52
3.4.6 Preventive maintenance ...... ......................................................................................... .......... 3-60

CHAPTER 4
DISASSEMBLY/ASSEMBLY AND ADJUSTMENT
4.1 General.. ............................ ............................................................................................... 4-1
4.2 Tools and Measuring Instruments
... ................................................. ...................... ........................ 4-1
4.3 Disassembly and Assembly................................................ ....................................................... 4-2
4.3.1 Removal of upper case.... ...... .......................................... ..................................................... 4-2
4.3.2 Removing the circuit boards.. ....................................... ........................... ....................... 4-3
4.3.3 Removal of Model-3660 printer mechanism................................................ ........................... 4-6
4.3.4 Removal of fan set UB (head cooling fan). ..................................................................... 4-6
4.3.5 Removal, installation and adjustmnent
of print head.........
.... ................................................... ...................................................... 4-7
4.3.6 Removal of CPU and ROM.
... ...... ........ ........................................................................ 4-9
4.3.7 Adjustment of print alignment (backlash)..................................................................... 4-10
4.4 Adjustment.........................
4-12
4.4.1 MTS and DTS sensor board adjustment.. .................................................................................. 4-12
4.4.2 H.P. sensor board adjustment .................................................................................................. 4-1 4
4.4.3 Backlash of the carnage motor and belt driving pulley.............................................................. 4-15
4.4.4 Backlash of the paper feed motor and
paper feeding reduction gear ........... ................................. ...................................................... 4-16
CHAPTER 5
TROUBLESHOOTING
5.1 Entry of Troubleshooting ......... ................ .................................................. ....................
.,
5-1
5.2 Check-out Procedure ..... ....... ..... ........ .......................................... ......................
.,.,
5-4
5.3 Unit Repair Flow Chart (UXMCL). .......... ..... ........................................................................ 5-18
5.4 Unit Repair Flow Chart (UXDRV) ........ ................................................................................................ 5-33
5.5 Unit Repair Flow Chart (UXPS). ...... .................................................................................................... 5-40
5.6 Unit Repair Flow Chart (IUPIF) ............................. ......... .................................................... 5-42
CHAPTER 6
MAINTENANCE
6.1 Maintenance ....................... ........ ......... ..... ...............................................................................
6.1 .1 Cleaning.. ............
... ... ................ ...... ........................ ...........................................
6.1 .2 Inspection.. ................
... .... .... ............................................................................................
6.2 Lubrication.. .............................
.... .....................................................................................................
6.2.1 Lubricants.. ........... ...... ...... .......... ........ ........................................................................
6.2.2 Lubrication requirement .......................................................................................................
6.2.3 Lubrication point.. .....................................................................................................................
6.2.4 Adhesive application requirements .................................... ....... ............. .............................
6.2.5 Adhesive application points...............................................
.... ....
........... ...............................
6.2.6 Lubricants and adhesives list.. ...............................................................................................
6-1
6-1
6-1
6-2
6-2
6-2
6-2
6-3
6-3
6-4
CHAPTER 7
APPENDIX
II
List of principal IC’s.. ................. ...... ...................................................................................................... 7-1
Description of principal IC's .......
... ........................................................................................................ 7-2
Exploded diagram for LQ-1500.................................................................................................................. 7-35
Lubrication and adhesive application points drawing A ............................................................................. 7-36
Lubrication and adhesive application points drawing B.. ............................................................................ 7-37
Lubrication and adhesive application points drawing C.............................................................................. 7-38
UXMCL circuit diagram............................................................................................................................... 7-39
Component layout of UXMCL board. ......................................................................................................... 7-40
UXDRV circuit diagram.............................................................................................................................. 7-41
Component layout of UXDRV board........................................................................................................... 7-42
UXPS circuit diagram............................... ................................................................................................. 7-43
Component layout of UXPS board.............................................................................................................. 7-44
PSU 24E circuit diagram............................................................................................................................. 7-45
Component layout of PSU 24E board ........................................................................................................ 7-46
UXFIL circuit diagram ..................... .......................................................................................................... 7-47

INTRODUCTION
This technical manual describes the principle of mechanical and electrical
operations, as well as the maintenance and repair procedures, of the EPSON
LO-1500 Dot Matrix Printer.
Chapters 4 through 6 of the manual deal with the fundamental troubleshoot-
ing, maintenance and repair of the LO-1500.
For detail on the disassembly, assembly, troubleshooting and maintenance of
the Model-3660 Printer Mechanism, refer to the separately published “Techni-
cal Manual of EPSON Model-3660”.
* The contents of this manual are subject to change without notice
Ill

CHAPTER 1
GENERAL
1 .1
Product Overview................................................................................... 1-1
1.2 LQ-1500 Interface Overview ................................................................ 1-1
1.3 General Specifications........................................................................... 1-1
1 .4
Major Components................................................................................. 1-4

1 .1 Product Overview
The LO-1500 is a serial terminal printer, featuring 200 CPS, bi-directional printing (draft pica mode) with
logical seeking capability, and 24 x 24 dot-matrix character formation. All interfaces for the LO-1500
which permit connection of the printer to various computers are optional. The interface circuit boards are
cartridge type, which can be set snugly into the housing.
Should maintenance or repair be required, the printer mechanism and circuit boards of the LQ-1500 are
readily replaceable. The technician can perform maintenance and repair quite easily by referring to this
manual.
1.2 LQ-1500 Interface Overview
(1) Centronics-compatible, parallel interface
This standard communication link permits data exchange with many computers without modification
or addition of other peripheral devices.
(2) RS-232C/Current Loop Serial Interface
A 20 mA current loop type, serial interface which permits the printer to receive data at a bit rate
ranging from 75 to 19200 BPS.
(3) IEEE-488 Interface
An optional interface which permits parallel communication between the printer and any computer or
measuring instrument which is equipped with bus structure conforming the IEEE-488 Std.
488-l975.
1.3 General Specifications
(1 ) Printing Method . . . . . . . . . . . . . . . . . . . . . . . .._......
Impact dot matrix
(2) Character . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1. Draft
2. Near letter quality (LO)
3. Proportional (standard)
4. Multi-font (with option card)
5. Super/subscript in each above character style. (1 to 4.)
(3) Character Structure
Character Normal Super/Subscript
Draft
9 x 17 font
7 x
11 font
LO
15 x17 font
11 x
11 font
ProportIonal
37 x 17 font
23 x
1 1 font
(4) Character Size SeeTable1. on the page 1-3
(5) Column Width.................................. See Table 1. on the page 1 - 3.
(6) Print Speed ........................................ See Table 1. on the page 1 - 3.
(7) Paper Feed ..................................... Friction feed (standard)
Adjustable tractor feed (option)
(8) Paper
@ Cut sheet
Paper width ..,,._.......................... 182 mm to 364 mm
Paper thickness . 0.06 mm to 0.1 mm
Weighing .._.............. .45 kg to 70 kg (52 to 82 g/m*)
1-1

@ Fanfold paper
paper width
101 mm to 406 mm
Copies
4 sheets max. (include original)
Paper thickness and Weight
Notes:
1. Jointing finish of copies should be point or line pasting.
2. Release the friction feed during the tractor feed operation.
3. Set the head adjusting lever as shown in above table.
However, adjust the step setting within range +1 step, depending on print density.
(9)
Paper Insertion ...........................
(1 0) Line Spacing ..................................
(1 1)
Print Direction................................
(1 2) Line Feed Repeat Rate ....................
(1 3)
Ribbon.. ...........................................
Rear
1/6”, 1/8” or programmable
Bidirectional printing with logical seeking.
In bit image and double-strike mode, unidirectional printing from
left to right is selected when the power is ON.
Bidirectional printing is also possible using ESC U.
120 ms/line (when 1/6” line feed is performed intermittently)
100 ms/line (when 1/6” line feed is performed continuously)
Exclusive cartridge ribbon (Black)
1-2

Table 1
1-3

1.4 Major Components
The LQ-1500 consists, in a broad classification, of the following five major components
(I ) Housing
(2) Model-3660 printer mechanism
(3) Control circuit boards
(4) Interface circuit boards
(5) Power supply circuit boards
The housing of the LQ-1500 consists of an upper case and lower case. The lower case is designed to
facilitate mounting of the following components.
Circuitry for the LQ-1500 is located on five different boards: the UXFIL and UXPS/PSU 24E boards which
house the power supply; the UXMCL board, which contains most of the control circuitry; the UXDRV,
which handles print mechanism drive circuitry, and a interface board (IUPIF or IURS or IUIE) which serves
as computer interface.
1-4

(1) Housing (Fig. 1 .1)
Fig 1 .1 Upper and lower cases
(2) Model-3660 printer mechanism (Fig. 1.2)
The mechanism is an assembly of all the mechanical components including two stepper motors, a print
head, a ribbon feeding mechanism, a carriage assembly, sensors, and a frame section. One stepper
motor operates the print head carriage, while the other works as the paper feed motor. The
Model-3660 is designed to permit easy maintenance.
‘Fig. 1.2 Model-3660 printer mechanism
(3) Contrl circuit boards (Fig. 1.3)
The control circuit is distributed between two circuit boards, the UXMCL and UXDRV.
The UXMCL circuit board performs the central processing, and the UXDRV circuit board drives the
Model-3660 printer mechanism.
Fig. 1.3 Control circuit boards
1-5

(4) Interface circuit boards (Fig. 1 .4)
An interface circuit board exchanges data between the host computer and UXMCL circuit board.
Fig. 1.4 Interface circuit board
(5) Power supply circuit boards (Fig. 1.5)
The power supply circuit of the LQ-1500, consists of two major components, the UXFIL and UXPS/
PSU 24E circuit boards. Both circuit boards are located in the rear righthand corner. The UXPS/PSU
24E circuit board supplies DC +24V, +12V, -12V and +5V to the control circuit and the interface cir-
cuit.
Fig 1.5 Power supply circuit board (100/120V version)
Fig 1.6 Power supply circuit board (220/24OV version)
1-6

CHAPTER 2
PRINCIPLES OF OPERATlON
2.1 General...............................................
.................................................... 2-1
2.2 Connection Diagram ............................................................................ 2-1
2.3 Connector Pin Assignment ................................................................. 2-3
2.3.1 Connector on UXMCL circuit board......................................... 2-3
2.3.2 Connector on UXDRV circuit board ......................................... 2-8
2.3.3 Connector on UXPS/PSU 24E circuit board........................... 2-12
2.4 Electrical Circuit ................................................................................... 2-13
2.4.1 Power circuit .............................................................................. 2-13
2.4.2 Reset circuit................................................................................ 2-22
2.4.3 Sensor circuit.............................................................................. 2-22
2.4.4 Carriage motor control circuit.................................................. 2-26
2.4.5 LF motor control circuit ............................................................. 2-34
2.4.6 Head driver circuit..................................................................... 2-37
2.4.7 Auto sheet load circuit .............................................................. 2-39
2.4.8 Other function ............................................................................ 2-40
2.5 Printer Mechanism............................................................................... 2-41
2.5.1 Operation .................................................................................... 2-41

2.1 General
This chapter provides the descriptron of signals at the various connectors electrically interconnecting such
major components as printer mechanism, control circuits, interface circuit, power supply circuit, and con-
trol pannel of EPSON LO-1500 Terminal Printer, and explains the operating principles of the various me-
chanism around the electric circuit of the printer.
2.2 Connection Diagram (Fig. 2.1)
Fig. 2.1 Connection diagram
2-1

The CPU Z-80A provides overall control of the LQ-1500. In addition the LQ-1500 is supported by two
slave CPUs: the 8042(8742), which controls the carriage motor; the 8041(8741), which controls the
paper feed motor.
Other major LSls include:
8255AC5 ,,._,_..,.,_.,........_._......_ Output port for head pin drive data
8259A _..........._....__................... Interrupt controller
8253-5 .___................_................ Timer counter
2764(231 28) .._._..._.....___....._.
ROM which stores control programs and character patterns
uPD41 6-3 ,.,,...,, ,,,,_....,.,,._.,__... RAM which is used as the input data and print data buffer
uPB6101 -009 ,......._........_.._.... Gate array which controls LSls by receiving control signals
from CPU Z-80A
Fig. 2.2 Block diagram

2.3 Connector Pin Assignment
2.3.1 Connector on UXMCL circuit board
1) Table 2.1 CN1 pin assignment
(a) Use ,,.,.......,,....,.,..,.............._............ Used for data exchange between the main circuit board and the
interface circuit board
(b) Number of pins ._,.,,..._.._...,,,,......_._.. 50
Table 2.1 Pin assignment (CN1 of UXMCL)
2-3

Note: “Direction” refers to the direction of signal as viewed from the UXMCL circuit board

2) Table 2.2 CN2 pin assignment
(a) Use . . . . . . . . . . . . . . . . . . Data exchange between the main circuit board UXMCL and the
driver circuit board UXDRV.
(b) Number of pins .._......................... 50
Table 2.2 Pin assignment (CN2 of UXMCL)
2-5

2-6

3) Table 2.3 CN3 pin assignment
(a) Use . . . . ..__..................__....,,..._........._.. To supply power from the power supply board UXPS/PSU 24E to
the main circuit board UXMCL.
(b) Number of pins _,,.._.._.,,,.._._,,..r....__._ 9
Table 2.3 Pin assignment (CN3 of UXMCL)
Note: “Direction” refers to the direction of signal as viewed from the UXMCL circuit board.
4) Table 2.4 CN4 pin assignment
(a) Use ,....,,...,.._...__.....__..._,.,,,_.,...._...._.. Signal exchange between the control panel on the UXMCL circuit
board.
(b) Number of pins _...,,...,,_,,,........._...... 8
Table 2.4 Pin assignment (CN4 of UXMCL)
Note: “Direction” refers to the direction of signal as viewed from the UXMCL circuit board.
2-7

5) Table 2.5 CN5 pin assignment
(a) Use ___...__....__..._.._.._._..._.__................. Exchange of head/home position signals between the printer me-
chanism Model-3660 and the main circuit board.
(b) Number of pins4
Table 2.5 Pin assignment (CN5 of UXMCL)
Note: “Direction” refers to the direction of signal as viewed from the UXMCL circuit board.
2.3.2 Connector on UXDRV circuit board
1) Table 2.6 CN1 pin assignment
(a) Use ._........_....................................... To supply power from the power supply board UXPS/PSU 24E to
the driver circuit board UXDRV.
(b) Number of pins4
Table 2.6 Pin assignment (CN1 of UXDRV)
2) Table 2.7 CN2 pin assignment
(a) Use .._.._._._...._._......_...._...
Data exchange between the driver circuit board and the
Model-3660 printer mechanism.
(b) Number of pins __..._._._.._.__..._......_.... 34
Table 2.7 Pin assignment (CN2 of UXDRV)
2-8