Atari 1025 Quick start guide

COPYRIGHT ©1983 BY ATARI, INC. ALL RIGHTS RESERVED.
No part of this publication may be reproduced by* any mechanical, photographic, or
electronic process, or in the form of aphonographic recording, nor may it be stored in
aretrieval system, transmitted, or otherwise copied for public or private use, without
permission from ATARI, Inc.
Published By:
ATARI, INC.
1265 Borregas Avenue
P.O. Box 427
Sunnyvale, California 94086

ATARI
1025™ PRINTER
FIELD SERVICE MANUAL

Atari believes that the information described in this manual is accurate and reliable,
and much care has been taken in its preparation. However, no responsibility, financial
or otherwise, shall be accepted for any consequences arising out of the use of this
material. Information contained herein is subject to change. Revisions may be issued
to advise of such changes and/or additions.
Correspondence regarding this document should be forwarded to Director of Technical
Support, Consumer Product Service, Atari, Incorporated, 845 W. Maude, Sunnvvale
California 94086. 7’

TABLE OF CONTENTS
Section
1
2
3
4
Title Page
INTRODUCTION vii
THEORY OF OPERATION 1-i
Introduction 1_1
Mechanical Theory 1_1
Print Head Mechanism and Operation 1-1
Space Mechanism and Operation 1-3
Ribbon Feed Mechanism and Operation 1-4
Paper Feed Mechanism and Operation 1-5
Paper Lock Release Mechanism 1-6
Paper End Detecting Mechanism 1-6
Electrical Theory 1_7
Introduction 1_7
8051 Microprocessor 1-g
8155 RAM I/O l_g
2732 EPROM l_g
Power Supply l_g
Print Head 1_8
SILKSCREEN AND SCHEMATIC 2-1
MAINTENANCE/TESTING AND TROUBLESHOOTING 3-1
Equipment Required 3_1
General Maintenance Precautions 3-1
Cleaning 3_2
Diagnostic Program for Testing the 1025 3-2
ROM Self-Test Procedure 3_7
Specfic Command Code Failures 3-7
DISASSEMBLY/ADJUSTMENT/ASSEMBLY PROCEDURES 4-1
Upper Cover Disassembly 4_1
PCB Disassembly 4_1
Printer Unit Disassembly 4_2
Transformer Replacement 4_2
Print Head Disassembly 4_2
Carriage Frame Disassembly 4_3
Space Motor Replacement 4_3
Space Belt Tension Adjustment 4-4
Space Belt Replacement 4_4
Platen Disassembly 4_5
Atari 1025 Printer
Field Service Manual

TABLE OF CONTENTS
Section Title Page
Platen Assembly 4-6
Platen/Print Head Adjustment 4-6
Platen/Paper Separator Adjustment 4-7
Carriage Frame Assembly 4-8
First Character Printing Position Adjustment 4-8
Inserting the Print Head 4-9
Printer Unit Assembly 4-9
PCB Assembly 4-10
Upper Cover Assembly 4-10
51025 DIAGNOSTIC FLOWCHART 5-1
6SYMPTOM CHECKLIST 6-1
7PARTS LIST 7-1
Mechanical Parts 7-1
Electronic Parts 7-3
8SERVICE BULLETINS 8-1
Atari 1025 Printer
Field Service Manual IV

LIST OF ILLUSTRATIONS
Figure Number Title •Page
1-1 Printing Mechanism 1-2
1-2 Spacing Mechanism 1-3
1-3 Ribbon Feed to Left 1-4
1-4 Ribbon Feed to Right 1-5
1-5 Paper Feed Mechanism 1-5
1-6 Paper Lock Release Mechanism 1-6
1-7 Paper End Detecting Mechanism 1-6
1-8 PCB Functional Block Diagram 1-7
1-9 Print Head Pattern of the Letter I1-9
3-1 Sample Diagnostic Printout 3-5
4-1 Printer Unit 4-11
4-2 Cover Unit 4-13
4-3 Carriage Assembly 4-15
4-4 Base Unit Assembly 4-17
4-5 Space Belt Tension Adjustment 4-4
4-6 Ribbon Assembly 4-19
4-8 Platen/Print Head Adjustment 4-7
4-9 Platen/Paper Separator Adjustment 4-7
4-10 First Character Printing Position 4-9
LIST OF TABLES
Table Number Title Page
3-1 Character Command Codes 3-4
Atari 1025 Printer
Field Service Manual v

INTRODUCTION
TW
The ATARI 1025 'Printer Field Service Manual is organized in eight sections.
•THEORY OF OPERATION -Overview of the mechanical and electrical
theory of the 1025.
•SILKSCREEN AND SCHEMATIC -The silkscreen of the PCB component
layout and the schematic of the PCB and print mechanism.
•MAINTENANCE, TESTING AND TROUBLESHOOTING -Procedures for
maintaining, testing and repairing the 1025.
•DISASSEMBLY/ASSEMBLY -Step by step instructions on how to disassemble
and assemble the unit for component level repair.
•DIAGNOSTIC FLOWCHART -Flowchart enabling the technician to test and
troubleshoot adefective 1025.
•SYMPTOM CHECKLIST -For the experienced technician, alist of symptoms
with their probable causes and remedies.
•PARTS LIST -All parts available for the mechanical and electrical repair and
maintenance of the 1025. r
•SERVICE BULLETINS -Section to be used to hold service bulletins released
by the Director of Technical Support. These bulletins include changes in
recommended repair procedures and required modifications for units in the
field.
vii
Atari 1025 Printer
Field Service Manual

SECTION ONE
THEORY OF OPERATION
INTRODUCTION
'j* ^
The ATARI 1025 1Printer is adesk top, receive only, serial .impact dot matrix
printer. The 1025 Printer connects directly to the ATARI computer or disk drive with
an I/O cable and receives its instructions thereby. It is auni-directional printer.
MECHANICAL THEORY
PRINT HEAD MECHANISM AND OPERATION
PRINT HEAD MECHANISM
The print head consists of the following:
•Wire Guide
•Yoke
•Armature Assembly
•Spacer
•Magnet Assembly
The print head is spring-loaded and contains apermanent magnet. It can be easily
removed and installed. It's mounted on the carriage that runs parallel to the platen
and is attached to the PCB at connector CN3.
PRINT HEAD OPERATION
When not operating, the armature is attracted by the permanent magnet (see Figure
1-1). The print wire, which is fixed to the armature, is held retracted within the wire
guide. When acharacter to be printed is detected by the control circuit, acurrent
flows to the coil corresponding to that print wire. When the coil is energized, the
magnetic flux generated by the permanent magnet is nullified. The print wire is then
driven toward the platen by force of the armature spring. Thus adot is printed on the
paper.
After printing the character, the magnetic flux of the permanent magnet attracts the
armature again so the print wire is retracted into the wire guide.
Atari 1025 Printer
Ffeid Service Manual
1-1

Inked Ribbon
Figure 1-1. Printing Mechanism
Atari 1025 Printer
Field Service Manual 1-2

SPACE MECHANISM AND OPERATION
SPACING MECHANISM
The space mechanism consists of the following:
•Pulse motor with synchro belt pulley
•Synchro belt
•Two guide shafts
•Carriage
•Home sensor
•Home sensor plate
Spacing and carriage return are performed by driving the carriage with apulse motor.
The carriage is guided by two shafts mounted parallel to the platen.
SPACING OPERATION
The carriage with the print head mounted on it moves parallel to the platen along the
upper and lower guide shafts (see Figure 1-2). One end of the carriage frame is fixed
to the synchro belt.
As the pulse motor turns clockwise, the carriage assembly is driven from left to right.
The spacing mechanism is designed so that when the pulse motor turns 4steps (30°),
the carriage moves 2.54 mm (1/10 inch).
CARRIAGE RETURN OPERATION
When the carriage return code (EOL) is received, the pulse motor is driven
counterclockwise by the signal from the control circuit. The carriage moves from
right to left until the home sensor plate enters the opening in the home sensor.
The home sensor consists of an LED photodiode pair. When the home sensor plate
enters the sensor, the light is interrupted and asignal is generated to stop the motor.
When the pulse motor stops, the carriage stays at the start position until the next line
is ready to be printed.
Guide Shaft (upper)
Figure 1-2. Spacing Mechanism
Atari 1025 Printer
Field Service Manual 1-3

RIBBON FEED MECHANISM AND OPERATION
RIBBON FEED MECHANISM
The ribbon feed mechanism consists of the following:
•Ribbon drive gear
•Ribbon gear
•Ribbon spool gear
•Ribbon change lever
•Eyelet detector lever
•Ribbon bracket
The space pulse motor used to drive the carriage also provides the power to feed the
ribbon.
RIBBON FEED OPERATION
When the space pulse motor's drive belt runs counter-clockwise, it engages the central
ribbon gear with the ribbon spool gear and winds the ribbon, while the opposite ribbon
spool turns freely. When the space pulse motor turns clockwise and the print head
moves from left to right, the central ribbon gear disengages and remains disengaged
until the motor direction reverses.
The eyelet detector lever indicates the direction in which the ribbon feeds. When this
lever is pushed to the left, the ribbon feeds left, and vice versa. When the ribbon is
nearly run out, the ribbon eyelet pushes the eyelet detector lever in the opposite
direction. The ribbon then feeds to the right in the same fashion as described above.
(See Figures 1-3 and 1-4 below).
Figure 1-3. Ribbon Feed to Left
1-4
Atari 1025 Printer
Field Service Manual

Figure 1-4. Ribbon Feed to Right
PAPER FEED MECHANISM AND OPERATION
PAPER FEED MECHANISM
The paper feed mechanism consists of the following:
•Pulse motor with gear
•Reduction gear
•Platen with fixed sprocket and friction roller
The printing paper is moved up to the next line as the pulse motor runs, meshes the
gears, and rotates the fixed pin platen.
PAPER FEED OPERATION
The paper feed pulse motor is mounted on the left side panel, and its rotation is
transmitted to the platen via the reduction gear (see Figure 1-5). The paper is fed
4.23 mm (1/6 inch) when the pulse motor advances 24 steps (180°).
Figure 1-5. Paper Feed Mechanism
Atari 1025 Printer
Field Service Manual 1-5

PAPER LOCK RELEASE MECHANISM
When the paper lock release lever is moved forward, the paper chute opens to allow
clearance between the pressure rollers ana the platen, thereby allowing insertion of
paper. When the paper lock release lever is moved back, the pressure rollers push
against the platen and feed the paper (see Figure 1-6).
Paper Lock Release Lever
PAPER END DETECTING MECHANISM
When paper is loaded, the paper prevents the microswitch actuator from dropping into
the paper-separator groove, as illustrated in Figure 1-7. This keeps the microswitch
turned off. When the paper runs out, the actuator drops into the groove to close the
microswitch and detect the absence of paper.
Atari 1025 Printer
Field Service Manual 1-6

ELECTRICAL THEORY
INTRODUCTION
The electronic portion of the 1025 is on one Printed Circuit Board (PCB). This PCB
receives the information serially from the computer console via one of the two
identical I/O plugs and then transfers this data into aseries of High and Low signals
which make one or more of the seven printer pins strike the paper, thereby forming
the proper character. Afunctional block diagram of the PCB is illustrated in Figure
1-8.
PRINTED CIRCUIT BOARD
ATARI
SERIAL
INTERFACE
CN6and*CN7
RI:ctifieR
J31REGULATt
1DR 1
KEUTIf 11
AC
SOURCE
AC CORD
RING CORE SWITCH
&FUSE
ICN1
TRANS-
FORMER
PRINT HEAD
SPACE
PULSE MOTOR
tCNIO 1 c
J
1CN9 pf
j^
,CN8 j,
jL
f
cQzQjMOTOR SENSOR
-jpowejr FRoNT
PANEL
Figure 1-8. PCB Functional Block Diagram
Atari 1025 Printer
Field Service Manual 1-7

3051 MICROPROCESSOR
The microprocessor controls the overall functioning of the printer. It reads the
information the computer wants printed through the I/O cable, looks up the proper
character in the ROM chip and by controlling aseries of High and Low signals prints
the character on the paper.
The microprocessor operates off a7.37 MHz clock, which acts as the known frequency
whereby all functions of the MPU are timed to interact.
8155 RAM I/O
This chip has two functions:
1) It provides the Random Access Memory storage for the printer, that is, it
stores information that is subject to change (for example, which character
set is currently being used).
2) The 8155 also controls the driver lines that operate the line feed and space
motors.
2732 EPROM
This chip contains the information that determines how the characters are formed in
all of the different type faces.
POWER SUPPLY
The 110V A/C is fed into atransformer by the power cord. 26VAC and 10VAC are
output. The 26VAC runs through abridge rectifier and supplies voltage to the motors
and print head. The 10VAC runs through arectifier and supplies 10VDC to the printer
and a5V regulator. This regulator delivers the voltage to the logic circuitry of the
PRINT HEAD
The following discussion describes what occurs electronically in order to print the
Letter I. The computer console signals the 1025 to get ready to print aletter by
pulling the command line (pin 7of CN6 or CN7) Low. This in turn pulls down pin 14 of
Q8. The computer then sends the information to the microprocessor via the Data In
line. If the printer did not for any reason accept the information sent by the
computer, it sends acode back to the computer telling it what caused the failure. If
the processor accepts the computer's information, it temporarily stores it in the 8155.
It then looks up what the print head pattern should be for that character, as
determined by the information permanently stored in the ROM, and gets ready to print
Atari 1025 Printer
Field Service Manual 1-8

To print the letter the print head strikes in aseries of vertical rows, but only with the
pins required to form the letter. After the first column has been printed, which occurs
when the proper lines drop Low, the space motor advances one row as aresult of a
Low signal from the 8155. When the print head has been advanced to the next column,
it again strikes the proper dots. The above steps are repeated until the letter Iis
formed as in Figure 1-8 below.
Figure 1-9. Print Head Pattern of the Letter I.
Atari 1025 Printer
Field Service Manual 1-9