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EK-0LA50-TM-001

March 1983

104 pages

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Document:	LA50 Printer Technical Manual
Order Number:	EK-0LA50-TM
Revision:	001
Pages:	104
Original Filename:

OCR Text

EK-OLASO-TM-001

LASO Printer
Technical Manual

EK-OLASO-TM-001

LASO Printer
Technical Manual

Prepared by Educational Services
of
Digital Equipment Corporation

1st Edition, March 1983
Copyright© 1983 by Digital Equipment Corporation. All Rights Reserved.
Printed in U.S.A
The reproduction of this material, in part or whole, is strictly prohibited. For
copy information, contact the Educational Services Department, Digital
Equipment Corporation, Maynard, Massachusetts 01754.
The information in this document is subject to change without notice. Digital
Equipment Corporation assumes no responsibility for any errors that may
appear in this document.
The following are trademarks of Digital Equipment Corporation, Maynard,
Massachusetts.
Digital logo
DEC
DECmate
DECnet
DEC US

DECwriter
DIGITAL
LA
MASSBUS
PDP

P/OS
Professional
Rainbow
RSTS
RSX

UNIBUS
VAX
VMS
VT
Work Processor

CONTENTS

CHAPTER 1 GENERAL DESCRIPTION
1.1
1.2
1.3
1.4

CHAPTER 2

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Physical Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Related Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1
1-1
1-2
1-4

INSTALLATION

2.1
2.2
2.3
2.4
2.5
2.5.1
2.5.2
2.5.3
2.5.4
2.6

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Site Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Unpacking and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Repacking Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Installation Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Ribbon Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Paper Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
Power Up and Checkout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Interface Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
Configuration Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

CHAPTER 3

OPERATOR INFORMATION

3.1
3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.3

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operator Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Internal Self-Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Carriage Motion Self-Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Print Self-Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loopback Self-Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operator Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

111

3-1
3-1
3-3
3-3
3-3
3-4
3-4

CHAPTER 4
4.1
4.2
4.3
4.4
4.4.1
4.4.2
4.4.2.1
4.4.2.2
4.4.2.3
4.4.2.4
4.4.3
4.4.4
4.4.5
4.4.5.1
4.4.5.2
4.4.5.3
CHAPTER 5
5.1
5.2
5.2.1
5.2.2

THEORY
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Functional Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
Description of Functional Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
Microprocessor/Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
Communications and I/0 Data Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
Data Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
Baud Rate Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
Interface Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
Printhead Positioning and Printing Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
Paper Advancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
Input Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
TROUBLESHOOTING
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Self- Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Troubleshooting Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-1
5-1
5-2
5-2

CHAPTER 6

SERVICING

6.1
6.2
6.2.1
6.2.2
6.2.3
6.2.4
6.2.5
6.2.6
6.2.7
6.2.8
6.2.9
6.2.10
6.2.11

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
Removal and Replacement Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
Printer Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
Operating Voltage Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
Fuse Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9
Printhead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11
Printhead Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12
PCB Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
Paper Bail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14

6.2.12
6.2.13
6.2.14
6.2.15
6.2.16
6.2.17
6.2.18
6.3

Platen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16

Change-Gear Arm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 7
Ribbon Wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-18
Front Panel and Carriage Stop Switch Assembly-RA, RD/Front Panel,
Carriage Stop Switch and Access Cover Interlock Switch
Assembly- RB, RC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-19
Paper-Out, Access Cover Interlock and Carriage Sensor Switch
Assembly-RA, RD/Paper-Out and Carriage Sensor Switch
Assembly-RB, RC ................................................... 6-20
Tractor Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21
Carriage Wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-22
Carriage Motor ...................................................... 6-25
Line Feed Motor .................................................... 6-26
Power Transformer, Power Switch, and Noise Filter . . . . . . . . . . . . . . . . . . . . . . 6-27
5 V Transistor or Carriage Transistor Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . 6-29
Lubrication ............................................................ 6-30

APPENDIX A

PARTS LIST

APPENDIX B

ESCAPE SEQUENCE AND SWITCH SUMMARY

APPENDIX C

GLOSSARY

APPENDIX D

SPECIFICATIONS

FIGURES
1-1
1-2
1-3
2-1
2-2
2-3
2-4
2-S
2-6
2-7
2-8
2-9
3-1
3-2
3-3
4-1
4-2
4-3
4-4
4-S
4-6
4-7
4-8
4-9
S-1
6-1
6-2
6-3
6-4
6-S
6-6
6-7
6-8
6-9
6-10
6-11
6-12
6-13
6-14
6-lS
6-16
6-17
6-18
6-19

LASO Printer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
ASCII Chart........................................................... 1-2
Simplified Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Printer Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Unpacking/Packing Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Packing Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Ribbon Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-S
Paper Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
Pinfeed Paper Insertion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2- 7
Single Sheet Paper Insertion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Cable Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
Configuration Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10
Controls and Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Print Test Pattern....................................................... 3-3
EIA Loopback Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
LASO Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Microprocessor/Control System Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
Serial Character Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-S
Data Handling in the USART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
Creation of Baud Rate Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
Printing and Positioning Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
Paper Feed Subsystem .................................................. 4-11
Line Feed Motor Phase Patterns ......................................... 4-12
Power Supply and Wake-Up Functional Diagram .......................... 4-13
Physical/Functional Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S-1
Assembly Removal Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
Paper and Access Covers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
Cover Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
Carriage Stop Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
Panel Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4
Indicator and Switch Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-S
Bottom Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
Printed Circuit Board Connector and Fuse Locations . . . . . . . . . . . . . . . . . . . . . . . . 6- 7
Power Supply Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8
AC Line Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9
PCB Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10
Printhead Clamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11
Printhead Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12
Printhead Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13
Print Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 S
Paper Bail ............................................................ 6-1 S
Platen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16
Carriage Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 7
Ribbon Wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-18

6-20
6-21
6-22
6-23
6-24
6-25
6-26
6-27
6-28
6-29
6-30

Cover Interlock-Model RB, RC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-19
Tractor Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21
Carriage Drive Assembly ............................................... 6-22
Carriage Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-23
Carriage Retainer ...................................................... 6-23
Carriage Wire Installation ............................................... 6-24
Carriage Wire Tension Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-25
Line Feed Motor Replacement ........................................... 6-26
Paper Thickness Lever . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-28
5 V Transistor and Carriage Transistor Assembly .......................... 6-29
Lubrication Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-31

TABLES
1-1
2-1
2-2
2-3
2-4
2-5
2-6
2-7
3-1
3-2
3-3
4-1
5-1
6-1

Related Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Site Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
National Character Set ................................................. 2-11
Graphics Aspect Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
XON/XOFF and Ready/Busy Protocol ................................... 2-12
Right Margin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12
Baud Rate Select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12
Data Format .......................................................... 2-13
Controls and Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Self-Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Operator Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
Printer Interface Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
Troubleshooting Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
Lubrication Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-30

CHAPTER 1
GENERAL DESCRIPTION

1.1 GENERAL
The LASO (Figure 1-1) is a desk top, receive-only, microprocessor controlled, dot-matrix printer. The printer is available in four models to meet international power requirements. They are the model LASO-RA,
LASO-RB, LASO-RC, and LASO-RD which operate at 120 Vac, 220 Vac, 240 Vac, and 100 Vac respectively. Print modes are either text or graphic. In the text mode, characters define the functions and character symbols usually associated with alphanumeric printers. In the graphic mode, characters define one of 64
possible I X 6 dot combinations for print. The LASO receives characters and commands through an asynchronous serial interface at selectable baud rates from l l 0 to 4800 baud.
1.2 PHYSICAL DESCRIPTION
The LASO main assemblies consist of the printer mechanism, printhead, and the printed circuit board
(PCB). The PCB is reached through the bottom of the printer and contains the logic, control, and power
supply circuits.

Figure l-1

LASO Printer

1-1

1.3 FUNCTIONAL DESCRIPTION
The LASO is a receive-only printer which operates as an output device for a computer. Input buffer capacity is 2047 characters. The printer receives and interprets information from the computer and prints it out.

The standard character set for the LASO is based on the US ASCII character set (Figure 1-2) which
includes 94 upper- and lowercase printable characters. In addition, the printer can print the 81
Multinational, the 63 JTS Katakana, the 27 VTlOO Special Graphics, and the error indicator.
87

0
0

86
85

BITS

.---

COLUMN

84 83 82 Bl ROW

1
OLE

0
0

2
SP

0
1

60
48
30

3
40
32
20

1
0

1
1

140
96
60

160
112
70

141
97
61

161
113
71

142

162
114

NUL

0
0
0

SOH

1
1
1

DC1

21
17
11

41
33
21

61
49
31

101
65
41

121
81
51

STX

2
2
2

DC2

22
18
12

0 0

42
34
22

62
50
32

102
66
42

122
82
52

ETX

3
3
3

DC3
(XOFF)

23
19
13

43
35
23

63
51
33

103
67
43

123
83
53

143
99
63

163
115
73

(XONl

20
16
10

1
1

100
64
40

120
80
50

98
62

0 0

EOT

4
4
4

DC4

24
20
14

44
36
24

64
52
34

104
68
44

124
84
54

144
100
64

164
116
74

ENQ

5
5
5

NAK

25
21
15

45
37
25

65
53
35

105
69
45

125
85
55

145
101
65

165
117
75

ACK

6
6
6

SYN

26
22
16

46
38
26

66
54
36

106
70
46

126
86
56

146
102
66

166
118
76

7
7
7

ETB

27
23
17

47
39
27

67
55
37

107
71
47

127

BEL

147
103
67

1 0

10
8
8

CAN

30
24
18

(

50
40
28

70
56
38

110
72
48

130
88
58

150
104
68

167
119
77
170
120
78

11
9
9

31
25
19

)

51
41
29

71
57
39

111
73
49

131
89
59

151
105
69

1('

12
10
A

SUB

32
26
1A

52
42
2A

72
58
3A

112
74
4A

132
90
5A

152
106
6A

ESC

33
27
18

53
43
28

;

73
59
38

113

[

133
91
58

34
28
lC

54
44
2C

74
60
3C

114
76
4C

55
45
20

75
61
30

115
77
40

]

134
92
5C
135
93
50

56
46
2E

76
62
3E

116
78
4E

77
63
3F

117
79
4F

13
11
8

14
12

15
13
D

35
29
1D

16
14
E

36
30
1E

17
15
F

37
31
1F

KEY

ASCII CHARACTER

57
47
2F

ESC

...._

Figure 1-2

OCTAL

DECIMAL

18 .... HEX
....__

ASCII Chart
1-2

75
48

87
57

136
94
5E
137
95
5F

171
121
79
172
122

153
107
68

{

173
123
78

154
108
6C
155
109
60

174
124
7C

}

175
125
70

m
n
0

156
110
6E
157
111
6F

DEL

176
126
7E
177
127
7F

Characters are printed by moving a 9-wire, solenoid-operated printhead horizontally along the print line
and then firing groups of discrete wires at each printing position to form 7 X 9 dot-matrix characters. An
enhanced mode prints 13 X 9 dot-matrix characters. The graphics mode printing process involves creating
a single vertical column of up to six dots for each character received.
The printer uses single sheet or pinfeed paper, a plug-in printhead, and a disposable ribbon cartridge. The
printhead and ribbon mount on the carriage assembly and are easily reached for removal and replacement.
A reversible motor drives the carriage assembly horizontally and a stepper motor drives the platen which
advances the paper vertically. A ribbon drive mechanism in the carriage assembly advances the ribbon as
the carriage moves. Control logic circuits on the PCB synchronize printhead position by print commands.
A programmed microprocessor on the control/logic PCB controls input/output, character printing, and
forms control. Figure 1-3 shows a simplified block diagram of the LASO printer.

DATA IN

CONTROL

COMMUNICATIONS
LOGIC

MICROPROCESSOR
MEMORY AND
CONTROL

INTERNAL MICROPROCESSOR CONTROL BUS

pRINTERMECHANiCs I

I
PRINT
AND
PAPER
FEED
CONTROL
LOGIC

I
I
I
I

L ____ _JI
MA-9681A

Figure 1-3 Simplified Block Diagram

1-3

1.4 RELATED DOCUMENTS
Table 1-1 lists all the documentation available to support the LASO printer.

Table 1-1 Related Documents
Title

Document
Number

Description

Installing and Using
the LASO Printer

EK-OLA50-UG

Installing and operating
the printer

LASO Printer
Programmer Reference
Manual

EK-OLASO-RM

Programming and
interfacing the printer

LASO Pocket Service
Guide

EK-OLA50-PS

Troubleshooting and
mechanical servicing
information

LASO Technical
Manual

EK-OLA50-TM

Installing, operating,
theory of operation,
detailed troubleshooting,
and mechanical servicing
information

LASO Illustrated
Parts Breakdown

EK-OLA50-IP

Exploded views and parts
lists

LASO Field
Maintenance Print Set

000-9SS

Engineering drawings

1-4

CHAPTER2
INSTALLATION

2.1 GENERAL
This chapter contains the step-by-step procedures to inspect, install, power up, and check out the printer.
These procedures allow you to verify that the printer is not damaged and is operating properly before you
connect it to the communication system.
2.2 SITE CONSIDERATIONS
Install the printer in an area that is free from excessive dust, dirt, corrosive fumes, and vapors. Table 2-1
lists the environmental and power requirements of the printer. Figure 2-1 illustrates its overall dimensions.
Appendix D contains a complete list of specifications.
Table 2-1

Site Considerations

Consideration

Specification

Temperature

10° to 40° C (50° to 104° F)

Relative humidity

10% to 90%

Input voltage

Model LA50-RA
Model LA50-RB
Model LA50-RC
Model LA50-RD

Frequency range

47 to 63 Hz

Power consumption

Operating: 180 watts maximum
Idling: 16 watts

2-1

104 to 128 Vac
191to235 Vac
208 to 256 Vac
90 to 110 Vac

MA-10,386-C

Figure 2-1

Printer Dimensions

2.3 UNPACKING AND INSPECTION
Use this procedure to unpack and inspect the printer. You need a sharp instrument to perform this
procedure.
1.

Open the top of the shipping carton (Figure 2-2).

Lift the printer up and out of the carton. Place it on a flat, clean work surface.

Remove the shock absorbing material and packing from around the printer.

Remove the documentation package, power cord, and ribbon.

Carefully inspect the printer for obvious shipping damage. Check for lost or missing items.
Report any damaged or missing items to the local carrier and your Digital branch office.

Remove the access cover and remove the cardboard retainer (Figure 2-3). Replace the access
cover.

If necessary, wipe the outer surfaces with a clean, soft, lint-free cloth.

2-2

. Details
Figure 2-2 Unpacking/P ackmg

2-3

CARDBOARD
RETAINER

MA-10,001A

.
2-3 Packing Removal
Figure

2-4

2.4 REPACKING PROCEDURES
Perform the following procedure to repack the printer for shipment.

Remove the ribbon cartridge, paper, and all cables.

Remove the access cover and secure the printhead with the cardboard retainer to prevent movement while in transit. Replace the access cover (Figure 2-3).

Repack the printer with the shock absorbing material (Figure 2-2).

Seal the shipping carton with reinforced tape.

2.5 INSTALLATION PROCEDURES
Perform the following procedures to install the printer.
2.5.1 Ribbon Installation
Perform the following procedure to install the ribbon.
I.

Remove the access cover.

Take up slack in the ribbon by turning the knob in the direction indicated by the arrow on the
cartridge.

Position the cartridge between the clips on the carriage and push down on the cartridge until it is
in place (Figure 2-4).

Replace the access cover.

MA·10,027C

Figure 2-4 Ribbon Installation

2-5

2.5.2 Paper Installation
The printer uses pinfeed or single sheet paper. The following procedure is for installation of pinfeed paper.
1.

Turn off power.

Open paper window (Figure 2-5).

Remove paper cover.

Pull bail bar away from platen.

Push paper release lever toward back of printer.

Open paper clamps (Figure 2-6).

PLATEN

MA-10,007A

Figure 2-5

Paper Installation

2-6

Position paper on tractor. If paper does not fit properly, use white tractor release levers to reposition tractors.

Close paper clamps.

Turn platen knob and guide paper behind platen.

10.

Advance paper until top of paper is behind bail bar.

11.

Push bail bar against platen.

12.

Replace paper cover.

13.

Close paper window.

MA-10,009A

Figure 2-6

Pinfeed Paper Insertion

2-7

The following procedure is for installation of single sheet paper.
1.

Turn off power.

Open paper window.

Pull bail bar away from platen.

Push paper release lever toward back of printer.

Push paper thr~ugh slot in paper cover and guide it to front of platen. Align paper (Figure 2-7).

Pull paper release lever toward front of printer.

Push bail bar against platen.

Close paper window.

Turn platen knob to reposition paper.

2.5.3 Power Up and Checkout
Use this procedure to power up the printer and verify that it is operational.
1.

Set the power switch to 0.

Plug the ac power cord into the ac power receptacle on the rear of the printer (Figure 2-8).

ALIGN

PAPER

r-----___,,,._

PLATEN KNOB

SLOT

PAPER
COVER

MA-10,013A

Figure 2-7 Single Sheet Paper Insertion

2-8

Plug the other end of the ac power cord into a nonswitched, grounded wall receptacle.

Insert paper into the printer.

Turn the power on. The POWER indicator should light.

Perform the self-tests described in Chapter 3, Paragraph 3.2.

After you have verified that the printer is operating correctly, turn off the power and connect
the interface cable to the system as described in Paragraph 2.5.4.

2.5.4 Interface Cable
The cable does not come with the printer. The following is a list of cables for system interconnection:
Cable

System

BCC05
BCC04
BC22A

Professional 300 Series and DECmate
Rainbow
Other

Use the following procedure to install the interface cable.
1.

Plug the system cable into the interface connector on the rear of the printer (Figure 2-8).

Install the other end of the cable as described in your system installation manual.

INTERFACE
CABLE
MA-10.006A

Figure 2-8 Cable Installation

2-9

2.6 CONFIGURATION SWITCHES
The LA50 printer must be compatible with computer hardware and software to communicate properly.
The configuration switches allow users to tailor the terminal to operate with a specific computer. They are
factory set for printer use with Digital systems.
To locate the configuration switches, remove the access cover and move the carriage to the left. Figure 2-9
shows the location of the switches and the labeled functions of each switch. To change a configuration
feature, move the tab with a small blade screwdriver, ballpoint pen, or equivalent.
CAUTION
Never use a lead pencil to change a switch position.
Broken lead or lead powder can cause a short or
intermittent problem to occur on the printed circuit
board.
GRAPHICS SWITCH
SW1-5
CHARACTER SET SWITCHES
SW1-1 THROUGH SW1-4

PROTOCOL SWITCHES
SW1-6, SWH

RIGHT MARGIN SWITCH
SW1-8

"\.. r"-,

BL991>E:lL

(SWITCHES ARE
AT FACTORY SETTINGS)

N3d0
Bl991>E:l L

N3d0
'-.-11.......,-1'-v-l

"'' '. "''"o'""/ \ \
DATA FORMAT SWITCHES
SW2-4 THROUGH SW2-6

BAUD RATE SWITCHES
SW2·1 THROUGH SW2-3

8L991>E:lL

OPEN~~~~~~~~~
N3d0
8l991>E:lL

CLOSED~~~vi}~~~
N3d0

MA-10,0278

Figure 2-9 Configuration Switches

2-10

Tables 2-2 through 2-7 show the switch positions for various system configurations.

Table 2-2 National Character Set
Switches SW 1-1 through SW 1-4 change the characters for multinational applications. When operating the
printer with Digital systems in an 8-bit environment, no change in settings is necessary.

Nation

SWl-1

Switch Positions
SWl-2
SWl-3

SWl-4

United States
Britain
Finland
France
French Canada
Germany
Italy
Japan
Norway /Denmark
Spain
Sweden

Open
Closed
Open
Closed
Open
Closed
Open
Closed
Open
Closed
Open

Open
Open
Closed
Closed
Open
Open
Closed
Closed
Open
Open
Closed

Open*
Open
Open
Open
Open
Open
Open
Open
Closed
Closed
Closed

Open
Open
Open
Open
Closed
Closed
Closed
Closed
Open
Open
Open

* factory setting

Table 2-3 Graphics Aspect Ratio
Switch SW 1-5 changes the horizontal to vertical dot ratio in graphic mode by changing the number of
horizontal dots per inch. The number of vertical dots are kept constant at 72 dots per inch.

Ratio

2: 1
2.5:1

Horizontal
Dots/Inch

Switch
Position

144
180

Open*
Closed

* factory setting

2-11

Table 2-4

XON/XOFF and Ready /Busy Protocol

Digital systems use XON/XOFF protocol. Other systems may require Ready /Busy protocol. Switch
SW 1-6 selects the protocol. Switch SW 1-7 selects the ready and busy signal levels.
Protocol

SWl-6 Position

XON/XOFF
Ready/Busy

Open*
Closed

Signal Level

SW 1-7 Position

Busy= High
Ready= Low

Open*

Busy= Low
Ready= High

Closed

* factory setting

Table 2-5

Right Margin

Switch SW 1-8 selects the method of controlling a line of characters that exceeds the eight inch line of print.
If set to truncate, the printer prints only the first eight inches of characters and drops the remaining characters. If set to wrap, the printer prints the remaining characters on the next line.
Selection

SWl-8 Switch Position

Truncate
Wrap

Open*
Closed

* factory setting

Table 2-6

Baud Rate Select

Switches SW2-1 through SW2-3 select the speed (bits per second) at which the printer communicates with
the computer.
Baud Rate

SW2-1

Switch Positions
SW2-2

4800
2400
1200
600
300
200
110

Open
Open
Open
Closed
Closed
Closed
Closed

Open
Closed
Closed
Open
Open
Closed
Closed

* factory setting
2-12

SW2-3

Open (factory setting)
Open
Closed
Open
Closed
Open
Closed

Table 2-7 Data Format
Switches SW2-4 through SW2-6 select the data format to enable communication with the computer.

Data Format

SW2-4

Switch Position
SW2-5

SW2-6

7 bits, plus odd parity
7 bits, plus even parity
7 bits, plus 8th bit mark
7 bits, plus 8th bit space
8 bits, plus odd parity
8 bits, plus even parity
8 bits, no parity

Open
Closed
Open
Closed
Open
Closed
Open

Closed
Closed
Open
Open
Closed
Closed
Open

Closed
Closed
Closed
Closed
Open
Open
Open*

* factory setting

2-13

CHAPTER3
OPERATOR INFORMATION

3.1 GENERAL
This chapter provides maintenance personnel with a summary of the printer controls and indicators. Figure
3-1 shows their locations and Table 3-1 describes their functions.
3.2 OPERATOR TESTS
If at any time there appears to be a problem in the printer, the operator may start a self-test. There are four
self-tests. Two of the tests provide the operator with a printout. Table 3-2 is a list of the self-test procedures
and the printer component areas under test.

Figure 3-1

Controls and Indicators

3-1

Table 3-1

Controls and Indicators

Control/Indicator

Function

READY indicator

The green READY indicator indicates the printer's operating
state. It is on when the printer is ready to print or is printing. If it is
off, the printer is not ready and will not start.

FAULT indicator

The red FAULT indicator blinks when the printer detects an
electronic fault. It stays on when the printer is out of paper.

POWER indicator

The green POWER indicator is on when you apply power to the
printer.

READY switch

The READY switch controls the printer's operating state.
Pressing the switch puts the printer in either the ready or not
ready state. In the ready state the READY indicator is on.

LINE FEED switch

Pressing LINE FEED advances the paper one line.

FORM FEED switch

Pressing FORM FEED advances the paper one full sheet.

Paper bail

The paper bail holds the paper against the platen. Red etch marks
on the bail help you position paper on the platen and locate the
horizontal printing position.

Paper thickness lever

The paper thickness lever adjusts the printhead position to allow
for different printing form thickness. Keep the lever close to the
platen for normal printing. Move the lever away from the platen
for thicker sheets and multicopy forms.

Paper release lever

The paper release lever controls paper holding tension. In the
forward position, paper is held tightly against the platen. In the
backward position, the paper is free for positioning or removal.

Platen knob

The platen knob allows manual control of the platen for paper
insertion, and for changing the paper's vertical position.

Table 3-2 Self-Test Procedures
Self-Test

Checkout

Internal
(runs automatically
at powerup)

Checks logic and memory

Carriage motion

Checks carriage motor and drive circuits

Checks line feed motor, carriage motor,
printhead and associated circuits. Does
not test communication lines

Loop back

Checks same functions as print self-test
plus the EIA transmit and receive lines

3-2

3.2.1 Internal Self-Test
This test checks the logic circuits on the printed circuit board (PCB). It runs automatically when power is
applied to the printer. The printing function is not energized during this test. The diagnostics include a
checksum test to verify all of the bits of the read only memory (ROM) and a pattern test to exercise and
verify all of the bits of the random access memory (RAM). If there is a failure, the FAULT light flashes.
3.2.2 Carriage Motion Self-Test
This test checks the carriage motor and drive circuitry. Its purpose is to verify that the carriage system
functions and that the mechanism is clear of obstructions. The printing function is not energized during this
test.
The test procedure is as follows.
1.

Start with the power turned off.

Press and hold the FORM FEED and LINE FEED keys and tum the power on.

Release the keys. The carriage should go through a scanning motion. If there is a failure, the
FA ULT light flashes or the test stops before it is complete.

Tum the power off to stop the test.

3.2.3 Print Self-Test
This test checks the logic circuits, line feed motor, carriage motor, and printhead. The test is useful for
general checkout of the printer and after changing an FRU. The test result is a printed pattern of the
ASCII character set (Figure 3-2).
The test procedure is as follows.
l.

Start with the power turned off.

Press and hold the FORM FEED key and tum the power on.

Release the key. The printing operation should start and continue until the power is turned off.
A flashing FAULT light, poor print quality, or failure of the test before completion indicates a
failure. A successful test is determined by examining the printed test pattern.

ABCDEFGHIJKLMNOPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz{i)- !"M$X&'<)*+,-./OI
BCDEFGHIJKLMNOPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz(i >- !"M$Y.&'<>*+,-./012
CDEFGHIJKLMNOPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz{i)- !"M$X&'C)*+,-./0123
DEFGHIJKLMNOPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz(i)- '"M$X&'<>*+,-./01234
EFGHIJKLMNOPQRSTUVWXYZC,JA_'abcdefghijKlmnopqrstuvwxyz(i)- !"M$X&'<>*+,-./012345
FGHIJKLMNOPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz(l)- !"M$X&'C)*+,-./0123456
GHIJKLMNOPQRSTLIVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyzCi >- !"M$X&'C)*+ 1 -./01234567
HIJKLMNOPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyzCl )- !"M$X&'<>*+,-,/01234567B
IJKLMNOPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz(i )- !"M$X&'()*+,-./01234567B9
JKLMNOPQRSTUVWXYZ [']A_' abcdefgh i jK 1mnopqrstuvwxyz {: )- ! "M$X&' <) *+ , - ./0123456789:
KLMNOPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz(l)- !"M$X&'()*+,-,/01234567B9:;
LMNOPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz(l )- ! "M$Y.&'()*+,-./0123456789:;<
MNOPQRSTLIVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz(l)- !'M$X&'C)*+ 1 -./0123456789:;<=
NOPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz{i)- !'M$X&'()*+,-./0123456789: ;<=>
OPQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz{i)- !"M$Y.&'()*+,-./0123456789: ;<=>?
PQRSTUVWXYZC'JA_'abcdefghijKlmnopqrstuvwxyz{i)- !'M$X&'()*+,-./0123456789: ;<=>?•
MA-10,016

Figure 3-2 Print Test Pattern

3-3

3.2.4 Loopback Self-Test
This test checks the logic circuits, line feed motor, carriage motor, printhead, and EIA transmit and receive
lines. The test is performed with a loopback connector (EIA PN 12-15336-01, Figure 3-3) that externally
connects the send data signals to the receive data signals.

The test procedure is as follows.
1.

Start with the power turned off.

Plug the external loopback connector into the printer interface receptacle.

Press and hold the LINE FEED key and turn the power on.

Release the key. The printing operation should start and continue until the power ·is turned off.
If the printer does not detect data on the receive data line within one second after the test starts,
the FAULT light flashes. A successful test is determined by examining the printed test pattern
(Figure 3-2).

3.3 OPERATOR TROUBLESHOOTING
If the printer does not start when you turn the power on, or if the printer appears to be defective, refer to
Table 3-3. This table describes the checks you should make before turning to the troubleshooting chapter.
CAUTION
Always turn off the printer before you attempt to
correct a problem.

CONNECTOR

FROM PIN

TOPIN

TO PIN

EIA
MA·7266B

Figure 3-3

EIA Loopback Connector

Table 3-3 Operator Troubleshooting
Symptom

Probable Cause

Remedy

Printer does not
start when power
is turned on.

Power cord not
connected, or
broken

Check power cord
connections. Check power
cord for damage.

Power source
fault

Check power at power
receptacle.

Fuse open

Make sure fuse is in
place. Replace fuse if
blown (Paragraph 6.2.3)

3-4

Table 3-3 Operator Troubleshooting (Cont)
Symptom

Probable Cause

Remedy

No printout.
FAULT light is
on. Pressing the
READY button
causes printer
to print one
line.

Printer out of
paper

Reload paper and press
the READY button.

No printout.
Pressing the
READY button
does not start
printer.

Access cover
open

Close cover and press the
READY button.

Light print.

Paper thickness
lever set
incorrectly

Reset paper thickness
lever to a position
closer to the platen.

Ribbon worn

Replace ribbon cartridge.

Paper thickness
lever set
incorrectly

Reset paper thickness
lever to a position
closer to the platen.

Printhead fault

Replace printhead
(Paragraph 6.2.4).

Missing dots in
print; always in
same row.

Printhead fault

Replace printhead
(Paragraph 6.2.4).

Paper jams.

Paper path
obstructed

Clear paper path.

Paper thickness
lever set
incorrectly

Reset paper thickness
lever to a position away
from the platen.

Tractors
positioned
incorrectly for
paper width

Release and reposition
the tractors. A void
pulling or compressing
paper.

Carriage moves,
but no printout

Pinfeed paper jams.

3-5

CHAPTER4
THEORY

4.1 GENERAL
This chapter describes the functions performed by the LASO printer. It also provides an understanding of
the printer's basic operating principles for field service personnel. Block diagrams and other drawings support the text.
4.2 INTRODUCTION
The LASO is a complete self-contained computer output hardcopy terminal. It consists of two basic components (exclusive of the enclosure), a control/logic board which contains the power supply, and the printer
mechanism. The LASO block diagram (Figure 4-1) shows these components and how they functionally tie
together.
The control/logic board manages the printing, paper advancing, and communication processes. All other
components and major options connect to it. The control/logic board includes the following functional
components:
•

A microprocessor to manage the overall terminal operation

•

2 X 8192 bytes of read only memory (ROM) containing a microprogram and standard set-up
parameters to operate the terminal with its specific features

•

2 X 2048 bytes of random access memory (RAM) for microprocessor temporary storage and
input/output data storage

•

An 1/0 buffer that provides an interface between the microprocessor and the electromechanical
components in the printer mechanism

•

An asynchronous serial receiver/transmitter (USART) for data exchange with the host
computer

•

An interval timer for control/logic system timing

The printer mechanism includes all of the mechanical and electromechanical components necessary for
impact printing and paper/forms control. This includes:
•
•
•

•
•

A 9-wire printhead
A carriage motor for horizontal printhead position
A stepper motor for vertical paper movement
A paper-out sensor
A platen, bail bar, and friction assembly

The power supply converts the ac power line into de voltages used by the printer. A de to de converter
transforms the regulated 5 volt de power source to +12 volts and -12 volts.
4-1

,-------

.r - - - - - -

1 PRINTER MECHANISM

CONTROL/LOGIC BOARD
MICROPROCESSOR
AND MEMORY

1/0 BUFFER
8155

DOT INTERRUPT
HORIZONTAL PITCH

RAM 2X2K
ROM 2X8K

"'
"'
"'"'w
::::i

u
0
a:
a..
0

+:-

a:
u

SPEED COMMAND

LF INTERRUPT
LINEFEED STEP

CARRIAGE'
MOTOR

CARRIAGE
SPEED
CONTROL

CARRIAGE
MOTOR
DRIVER

LINEFEED
CONTROL

LINEFEED
DRIVER

1------

INTERRUPTS

CLK COMMAND

INTERVAL
TIMERS/
COUNTERS

STEPPER
MOTOR

SYSTEM TIMER
8253

8251 SERIAL
RECEIVER
AND
TRANSMITTER

CARRIAGE

CARRIAGE
POSITION
COUNT

-----

PRINT
HEAD
SOLENOIDS

SOLENOID
DRIVERS

----POSITION

'•COMMUNICATIONS
SELECTOR

DOT
PRINT
CONTROL

DOT DATA

8085 µP

--....,

TO DRIVER
CIRCUITS

+5V
POWER
±12V
SUPPLY
TO
LOGIC CURCUITS ...__-......,,...----'

PAPER FEED

I
I

_J_ _ _ _ _ _ _ _ _ _ _J

"--'---.----'
EIA
INTERFACE

AC INPUT
MA-9609A

Figure 4-1

LASO Block Diagram

4.3 FUNCTIONAL OVERVIEW
The LASO receives characters from the host processor and examines them to determine if they are printable characters or commands. Specific character strings called escape sequences are used to change parameters such as vertical and horizontal character pitch, set tabs and margins, or to select alternate character
sets.
The functional areas of the LASO printer are divided for discussion into the following groups.
•
•
•
•
•

Microprocessor/control system
Communications and input/output data processing
Printfeed positioning and printing process
Paper advancing process
Power supply and power distribution

4.4 DESCRIPTION OF FUNCTIONAL AREAS
The LASO is a microprocessor-controlled system that uses the interaction of hardware circuits with firmware programs to perform control functions and provide functional characteristics. This paragraph
describes these functions and the hardware/firmware interactions that produce them.
4.4.1 Microprocessor/Control System
An 8085 microprocessor is the center of the LASO control system. The 8085 performs all the usual functions of a stored program computer: fetching instructions and data from ROM and RAM; and responding
to service requests from various devices in the system. Figure 4-2 shows the microprocessor/control system
logic. This includes the microprocessor chip, ROM/RAM memory, address decode logic, some command/
status buffering, and miscellaneous timing logic.

The Wake-Up (WU) signal holds the microprocessor RESET IN input low until the +S volt logic voltage
reaches its normal level. When WU goes high, the microprocessor program counter addresses location
0000 and the first instruction from memory is fetched and executed.
The microprocessor addresses memory and other devices with a 16-line address bus (A 15-AO). The high
address byte (Al5-A8) is asserted on the bus for the duration of the processor cycle. However, the low
address byte is asserted on the multiplexed 8-line address/data bus (AD7-ADO) for a short time at the
beginning of the cycle, so it must be captured in a register. Signals AD7-ADO pass through the low address
latch and are frozen for the remainder of the cycle by the falling edge of the address lines enable (ALE)
signal. The AD lines are then free for instructions and other input/output data for the remainder of the
cycle.
The microprocessor addresses devices on the address/data buses as either memory or 1/0. The output
signal IO/not memory (IO/M) makes the distinction. When low, IO/M enables memory (ROM/RAM) and
the 82S l USART. When high, 10/M enables the 8155 1/0 device. The 1/0 devices in the LASO system
are the many receivers and transmitters that communicate certain command and status information. 1/0
write addresses send commands to the printhead, carriage motor, and line feed drivers. 1/0 read addresses
get status on the cover interlock switch, paper-out switch and the configuration of the communication DIP
switches.

4-3

+5V~RESET IN

A15-A8

ADDRESS BUS

d"'""
cow

8085
MICROPROCESSOR
11)

LATCH

A15-AO

6Jj L~

,.....,

DECODER

CS78,80

O'OOW

~CSEO

CSAO

A7-AO

ROM MEMORY
L2764

cs co

~~M MEMORY

TO OTHER
FUNCTIONAL
AREAS

12)

CSC4

AD7-ADO

"T] ""lOUT

AST 7.5

ALE

CSC4
AO

AST 5.5

""""
""""

RD
WR

AST

AST 6.5

..:.

AST 7.5

1/0 READ
BUFFER

AD7-ADO
(2)
0

XTALC]

I
X2

REC DATA

..:.

AST 6.5

TIMER
8253

F"
RD

CLK OUT

cs co

AST 5.5

AST

CLK OUT

CSAO

(1)

I DODODDDDJ

RXC, TXC

INTER1---TER. ROY
FACE
BUFFER
!---SEND DATA
B251
RXD
t=REQ SEND
RXRDY
(1)

INTR

10/M
AST

COMMUNICATION
DIP SWITCHES

10/M

I, I

DOT9

•mecoc'~ '""'" ~"
LF

8155

TOF

PAPER OUT

TIME
OUT

ROY

(1)

FAULT LP
RXC
TXC

CSEO
MA-9629A

Figure 4-2

Microprocessor /Control System Logic

System timing is established by a crystal connected to the microprocessor. The microprocessor divides the
crystal operating frequency (running at 6.144 MHz) in half and produces the 3 MHz CLK OUT signal.
CLK OUT runs to other functional areas and produces printing and communications timing. The microprocessor runs continuously, fetching and executing instructions from memory so long as there are no interrupts. The microprocessor goes to a wait state whenever a write to, read from, or interrupt occurs. This
introduces a short time period called a wait state into the microprocessor cycle to allow more time for the
1/0 devices to respond.
When the LASO is turned on, a short initialization routine is run to verify all of the bits of the ROM and
RAM. After executing the initialization routine, the microprocessor goes to a monitor routine. The monitor
is basically a polling routine looking for status such as cover open, paper out, and any data to print or
process. Some internal status information may be too critical in nature to wait for the monitor loop to poll
for it. Hardware interrupts are used to handle this critical information or updating. Some examples are
items which must be handled in "realtime" such as processing high baud rate receiver data.
4.4.2 Communications and 1/0 Data Processing
The terminal interfaces to the host computer through a serial data port. The port includes a 82S 1A programmable universal synchronous or asynchronous receiver-transmitter (USART) and supporting logic.
The USART translates between parallel and serial data formats, adding or removing start and stop bits as
needed.
4.4.2.1 Data Format - The LASO printer communicates using serial characters. The serial character format used must be the same character format used by the computer. Serial characters are transmitted using
a start bit, seven or eight data bits, an optional parity bit and one stop bit (Figure 4-3). The number of bits
and the polarity of the parity (even or odd) is switch selectable. Parity errors can be detected for either
polarity.

IDLE
STATE OF

START BITOF
NEW CHARACTER

D:T~RB~TS
SPACE+
"MARK"

t
START
BIT

00 ~ ~1 ~ ~2 ~ ~ ~ ~ I ~ ~ ; ~ 07 i - ~STOP

LSB

..L -

..L~ ONE BIT
TIME=
ONE/
BAUD RATE

MSB

..1. -

.L /

BIT

.l.

WHEN
OPTIONAL RETURN TO IDLE
8-BIT
PARITY
STATE OF LINE
CHARACTERS
BIT
ARE USED
ath BIT=O
MA-7815A

Figure 4-3 Serial Character Format

4-S

4.4.2.2 Data Handling - The complete functional definition of the USART is programmed into the printer microprogram. A set of control bytes must be sent out by the microprocessor to initialize the USART to
support the desired communications format. Once programmed, the USART is ready to perform its communications functions. Figure 4-4 shows how data is handled across the serial line and in the printer.
Before further processing, the input buffer, which has a character capacity of 2047, temporarily stores all
characters except nulls and deletes. Nulls and deletes are ignored and do not occupy space in the input
buffer.
If the printer falls too far behind the incoming data, the input buffer overflows and data is lost. If characters are lost due to input buffer overflow, a single substitute control character (octal 032) is placed in the
input buffer at the point of loss. If a character is received with a parity error, the character is replaced in
the input buffer by the substitute control character (octal 032) thus causing the error character (reverse
question mark) to be printed. The 032 control character, thus indicates loss of characters, or a character
received with parity error.

When the printer is capable of printing, characters are fetched from the input buffer and printed or otherwise processed as required. When the printer is incapable of printing, the printer scans the input buffer for
printer status request control sequences even if the input buffer is full.
To avoid input buffer overflow, the XON/OFF protocol or Ready/Busy protocol synchronizes the data
source with the printer. Protocol selection is by an internal switch.

XON/XOFF Protocol
The XON/XOFF protocol synchronizes the data source with the printer as described below.
After successfully powering up and becoming enabled to send, the printer sends an XON control character
and constantly monitors the number of empty character positions in the input buffer. When the number is
less than 128, the printer sends an XOFF control character, signaling the data source to temporarily stop
sending data. Meanwhile, the printer continues to take characters from the input buffer and print or otherwise process them. When the number of empty positions in the buffer exceeds 224, the printer sends an
XON control character, thus signaling that transmission may resume.

RXRDY (RECEIVER FLAG)

INTR 1.-

8251A USART

AD7-ADO

"\(

----------

i-----,
2 ND
BUFFER

t-----

,_ - - - - - - PATH OF
CHARACTER
RECEIVED
(PARALLEL)

'\
I
I

1 ST
BUFFER

~'4---

RXD
RECEIVED
CHARACTER
(SERIAL)

t SZ_
8085 µP

CJCK

RAM
INPUT
BUFFER
MA-96088

Figure 4-4

Data Handling in the USART

4-6

The printer also sends an XOFF control character when it is not ready due to error conditions or operator
actions. Running out of paper or detecting a printhead position failure causes an XOFF control character to
be sent. The operator actions of opening the cover or placing the printer off-line also cause an XOFF control character to be sent.
The printer sends an XON control character when an XOFF state is present and all of the following conditions are true.
•

The printer is ready.

•

All fault conditions are cleared.

•

There are more than 224 empty positions for characters in the input buffer.
NOTE
At power up, an XOFF state is assumed.

The printer sends an XOFF control character when an XON state is present and any of the following
conditions are true.
•

The printer is not ready.

•

A fault condition occurs.

•

There are less than 128 empty positions for characters in the input buffer.

The printer sends an extra XOFF control character if more than 64 characters were received since the first
XOFF control character was sent.
Ready /Busy Protocol
The Ready /Busy protocol is functionally the same as the XON/XOFF protocol. However, instead of sending an XOFF control character, the printer places the Ready /Busy signal in the Busy state and instead of
sending an XON control character, the printer places the Ready /Busy signal in the Ready state.
4.4.2.3 Baud Rate Clocks - The LASO printer is programmed to perform serial 1/0 communication at
many different transmission rates, ranging from 110 to 4800 baud (bits per second). The rates are selected
by communication switch settings. Figure 4-5 shows the hardware (logic) that creates the baud rate clocks
used to shift the data stream.
The crystal controlled (6.144 MHz) microprocessor sends a CLK OUT signal to the interval timer (8253),
the 1/0 buffer (8155) and the USART (8251). The programmable frequency dividers within them scale
the CLK OUT signal down to the correct baud rate clock. Based on the selected baud rate (communication
switch setup or an escape sequence), command bytes from the microprocessor specify the mathematical
configuration (divisor value) of the frequency dividers. The interval timer divides the CLK OUT signal into
three clocks for system timing. The 1/0 buffer generates the transmit (TXC) and receive (RXC) clocks for
the USART buffers.

4-7

µP

AD7-ADO

8085
6,144
MHz
CRYSTAL

USART

8251

CLK OUT

'i;OBU
18155

...,
I
....----.. I

..----&----.

Fm ,

TIMER 1--~-T_xc_ _ _ TRANS/

CLK

L__ J

RXC

REC.
CONTROL

CLK
TO

I
I

BUFFER
____
...J

MA-0384-82

CLOCKS

Figure 4-5 Creation of Baud Rate Clocks

4.4.2.4 Interface Signals - The LASO data interface is RS-232C and RS-423 compatible. It includes a
25-position plug mounted on the rear of the printer for connection to an interface cable. Table 4-1 lists the
interface signals described in the following paragraphs.
Receive Data - The printer receives serial encoded characters on this line.
Send Data - The printer sends serial encoded characters on this line.
Although the bit rate within a character may be up to 4800 bits per second, the character transmission rate
from printer to host for any two characters does not exceed 100 characters per second.
When transmitting to the host the printer always includes at least two stop bits with each character.
Terminal Ready - The printer sends signals on the Terminal Ready line which indicate if the printer is
ready to send and receive data. When this signal is ON, the printer can send and receive data. When this
signal is OFF, the printer is not ready to communicate.
The terminal is ready to send and receive data after it completes its power-up initializations, and remains
ready to communicate indefinitely.
Request to Send - The printer maintains the Request to Send line in the ON condition indefinitely.
Ready /Busy - This line carries the Ready /Busy signal, depending on the setting of the Ready /Busy
Polarity switch. The printer is unable to receive characters if this signal is in the Busy state and is able to
receive characters if this signal is in the Ready state.
Protective Ground - This line is connected via removable jumper into the chassis ground of the printer.
The chassis is further connected to external grounds through the third wire of the power line cord.
Signal Ground - This line establishes the common ground reference potential for all other interface
circuits.

4-8

Table 4-1

Printer Interface Signals

Function

Direction

Receive Data
Send data
Terminal ready
Request to send
Busy or ready
Protective ground
Signal ground

To printer
From printer
From printer
From printer
From printer
From printer
Common

3
2
20
4
11
1
7

RS-232
Mnemonic

BB
BA

CD
CA
AB

4.4.3 Printhead Positioning and Printing Process
This paragraph describes how data stored in RAM buffers is processed and how characters are formed on
paper. It also describes how the system controls the printhead position and forms a character in the correct
location.
The LASO is an impact printer that uses a 9-element solenoid printhead. The printhead is driven horizontally and prints characters in a 7 X 9 dot matrix.
The printer can print double-width characters in 5, 6, and 8.25 character per inch modes. Therefore, the
maximum number of characters per line is 40, 48, and 66 respectively. Text or graphics mode printing is
selected by the control and escape sequences.
While processing characters in text mode, characters are printed as they are received. In graphics mode,
each character received defines a specific set of dots to be printed. A one-to-one relationship does not occur
between the sequence of received characters and the activity of printing. Each character selects 1 of 64
possible 1 X 6 dot combinations. This is done by using the top six elements of the nine-element head. The
ratio of horizontal to vertical dots is variable by changing the number of horizontal dots per inch with a
communication switch setting. The number of vertical dots is kept constant at 72 dots per inch. The ratio is
either 2: 1 or 2.5: 1.
Figure 4-6 shows a functional overview of the printing/printhead positioning process. The microprocessor/
control system issues a series of commands to the 8155 and printhead logic which contain instructions to
print a character. This includes character storage, carriage drive speed/direction, and a start print command. Speed depends on the selection of enhanced printing. The print direction is left to right in the graphics mode. In the text mode, printing is left to right as long as less than one received line remains unprinted.
If there is more than one line to be printed, the printer automatically goes to bidirectional printing. The
printhead position is determined by count from the start of print.
Carriage drive information, from the microprocessor, flows through the 8155 1/0 buffer to the motor
drivers and motor. Drive information and print information are coordinated by the 815 5 and microprocessor control logic. When a request is made to print a character, the ASCII-coded representation of the character stored in the RAM is transferred by the microprocessor to the LS374 register in the form of "dot
data" bytes. Each dot data byte has an encoded pattern of dot bits that fire specific head solenoids to create
the desired character on paper. If the printer is operating in graphics mode, a different type translation is
performed. Each graphic character sent by the host is processed and printed as one vertical pattern of dots.
When enabled by the control logic and print timing, the LS374 register fires the solenoids for the first
vertical dot pattern representation of the character. Immediately more dot data shifts into the register, the
carriage moves, and the printhead fires. The process continues until the character is completely printed at
which time the carriage and printhead wait for the next microprocessor command.
4-9

PRINTER MECHANISM

A15-A10

LS138
DECODER

PAPER

CSDC

+:-

CSCB

PLATEN
555
TIMER

ENABLE

LS374
REGISTER

DOT DATA
WIRES

µP8085
AD7-ADO

PRINTHEAD
DRIVER

CONTROL SIG.

8155
1/0 BUFFER

DRIVE

CARRIAGE
MOTOR
DRIVER

FIRE SOLENOID

DRIVE VOLTAGE

MA-9625A

Figure 4-6

Printing and Positioning Process

4.4.4 Paper Advancing
Paper is advanced by the paper feed subsystem which includes the following.

•
•
•
•
•
•

A stepper motor
A paper drive cluster gear
A platen assembly
Friction assembly
A pinfed tractor assembly
Control/logic circuitry on the printed circuit board

Figure 4-7 shows the paper feed subsystem. When the microprocessor/ control function identifies a line
feed character in the print buffer, it issues a series of commands to the 8155 1/0 buffer. These commands
include a control signal LFON and the four motor drive signals LFMA, LFMB, LFMC, and LFMD.
When the microprocessor sends a paper advance instruction to the 8155 1/0 buffer, the buffer sends a
LFON enable signal to the current switch. With this input, the current switch conditions the buffer/driver
to pass the drive signals to the line feed motor. In the holding mode, the LFON changes level and causes
the current switch to send a chopped drive current to the line feed motor. The chopped current keeps the
motor in position without overheating.
Motor rotation occurs when the signals to LFMB and LFMC are at a low level and at the same time the
signals to LFMA and LFMD are at a high level. This energizes the phase current to drive the motor one
step. By varying the phase pattern (Figure 4-8), the line feed motor continues the step sequence.
The rotary motion of the stepper motor armature is transferred through the paper drive cluster gear to the
platen assembly. With single sheet, the platen advances the paper by friction feed. With pinfeed paper, the
friction assembly is disengaged and the tractor pins push the paper into the platen assembly and around to
the front of the platen.

LFON

8155

8085
µP

1/0 BUFFER

GEAR

COM

LFMA

LF</>A

LFMB

CONTROL
LFMC
LFMD

BUFFER/
DRIVER

LF¢B
LF¢A
LF¢B
MA·0385-82

Figure 4-7 Paper Feed Subsystem

4-11

LF¢MA
LF¢MB

LF¢MC

LF¢MD
MA-0383-82

Figure 4-8

Line Feed Motor Phase Patterns

4.4.5 Power Supply - The power supply is located on the printed circuit board. The supply generates a
regulated +S Vdc, and unregulated +S Vdc and 27 Vdc. In addition, a de to de converter transforms the
regulated + S Vde to + 12 Vde and -12 Vde. Figure 4-9 shows a block diagram of the power supply. The
diagram includes a wake-up circuit. This circuit controls the initial state of the logic circuits during power
turn on and off.
4.4.5.1 Input Requirements - The ac input operating voltage for each model of the LASO is factory preset. The label on the fuse plate shows the power requirements. The models and their operating voltages are
as follows:
LASO-RA
LASO-RB
LASO-RC
LASO-RD

120 Vac
220 Vac
240 Vac
100 Vac

The operating power frequency range is between 47 and 63 Hz.
The plug-in position of a connector at the input to the power transformer allows changing the operating
voltage of the models. RA and RD models can operate at either 100 or 120 volts. RB and RC models can
operate at either 220 or 240 volts. Refer to Paragraph 6.2.2 for the voltage change procedure.
4.4.5.2 Outputs - The following lists the power supply outputs and their use.
+S Vdc regulated

Logic and control circuits

+S Vdc unregulated

Wake-Up/reset circuit

+ 12 Vde and - 12 Vde
regulated

RS232C output interface dual
line drivers

+ 27 Vde unregulated

Printhead, linefeed motor, and
carriage motor drivers.

4.4.5.3 Functional Description - The ac line voltage entering the supply is fused, filtered, and passes
through a voltage selection connector before going to the power transformer. The secondary of the transformer feeds two bridge-type full-wave rectifier circuits. A capacitor-resistor network smooths the 27 volt
output at one of the rectifier bridges. The other rectifier bridge supplies unregulated S volts directly from
the bridge and a regulated S volts after regulation by a series-feedback circuit.
The Wake-Up circuit senses when the 5 volts is turned on and resets the logic circuits. In addition, it controls the printhead and line feed motor drive circuits to prevent transients during power turn on and off.

4-12

5Vdc UN REG.

I RESET
WAKE-UP/
RESET

•

TRANSIENT CONTROL

+12Vdc
DC-DC
CONVERTER l-12Vdc

10V
2A
240V (RC)
120V (RA)

~
I

POWER

F~
NOISE
FILTER

POWER
SW

H-'--i

220V (RBI
100V (RD)

FILTER

REGULATOR

5Vdc REG

lllE+

COM

27Vdc UNREG
20V
3A

FILTER
I
2
COM
MA-0386-82

Figure 4-9

Power Supply and Wake-Up Functional Diagram

CHAPTERS
TROUBLESHOOTING

5.1 GENERAL
This chapter includes LA50 troubleshooting and repair information. When used with the text and functional block diagrams in Chapter 4 and the Field Service Engineering Print Set, this information should lead to
identifying and resolving any failure in the printer.
5.2 TROUBLESHOOTING
Troubleshooting a failure involves first identifying the type of failure by its symptoms. Then by referring to
the physical/functional block diagram (Figure 5-1 ), tables, and procedures, locating the most probable
field replaceable unit (FRU) that would cause that failure.

CARRIAGE
STOP
SWITCH

FRONT PANEL
ASSEMBLY

COVER
INTERLOCK
SWITCH (RB, RC)

CARRIAGE
MOTOR

PRINT
HEAD

5V TRANSISTOR
PRINTED CIRCUIT BOARD
CARRIAGE
TRANSISTOR ASSEMBLY
LINE FEED
MOTOR
PAPER-OUT
SWITCH

POWER
TRANSFORMER

POWER
SWITCH

AC
ENTRY

NOISE
FILTER

CARRIAGE
SENSOR
SWITCH

INTERFACE

EXTERNAL
...___ _ ___, CONNECTOR

INPUT
POWER
MA-10,398A

Figure 5-1

Physical/Functional Block Diagram
5-1

The symptoms displayed may represent more than one failure. Therefore, the symptoms may change as the
FRUs are replaced. Always troubleshoot to the current symptoms.
Spare parts do fail. The chance of a similar failure should not be ignored just because the FRU has been
replaced once.
At times the failure may be traced to a component of the FRU. However, as a general maintenance philosophy, troubleshooting to the component level is not recommended due to the cost of FRU spares versus the
cost of the added labor involved to find a bad component.

5.2.1 Self-Tests
Paragraph 3.2 describes the four types of self-tests available. Figure 3-2 shows the correct printer output
for the printout self-tests. You should run each of these self-tests and compare the resulting printer performance as part of the troubleshooting process. Then when you understand the problem symptoms better,
refer to the table and procedures in the following paragraphs.
5.2.2 Troubleshooting Tables
Table 5- l lists the most common LASO failures, the associated symptoms, and the appropriate corrective
action.
Table 5-1 Troubleshooting Checklist
Symptom

Probable Cause

Remedy

Printer does not
start when power
switch is set
to 1.

Power cord not
plugged in or is
broken

Check power cord
connections. Check power
cord for damage.

Carriage does not
move. Indicators
are off.

No power at
receptacle

Check power at power
receptacle.

AC line fuse
open.

Fuse not inserted
properly. Replace fuse if
blown (Para. 6.2.3).
Check power supply
connector for proper
plug-in orientation
(Para. 6.2.2).
If fuse continues to
blow, replace power
switch, transformer,
and noise filter assembly
(Para. 6.2.17).

PCB FU1-3A fuse
is open.

Replace fuse
(Para. 6.2.3).

Defective 5 V
transistor

Replace 5 V transistor
(Para. 6.2.18).

Defective PCB

Replace PCB (Para.
6.2.6).

5-2

Table 5-1

Troubleshooting Checklist (Cont)

Symptom

Probable Cause

Remedy

Printer does not
start. Carriage
does not move.
Indicators are on.

PCB FU2-SA fuse
is open.

Replace fuse (Para.
6.2.3). If fuse
continues to blow,
replace PCB (Para.
6.2.6).

FAULT indicator
flashes when power
is first turned on.

Defective PCB

Replace PCB (Para.
6.2.6).

Printer does not
start. Pressing
READY switch
does not start
printer.

Access cover is
open.

Close cover and
press READY.

Defective
interlock switch

Replace switch assembly
(Para. 6.2.12 for the
LASO-RA and RD, Para.
6.2.11 for the LASO-RB
and RC).

Printer does not
start. FAULT light
is on. Pressing
READY switch
causes printer
to print one line.

Defective
paper-out switch

Adjust paper-out switch
or replace switch
assembly (Para. 6.2.12).

When power is
applied, carriage
moves short
distance to right
and stops.

Defective
left carriage
sensor switch

Check if foreign material
is disabling switch. If
defective, replace switch
assembly (Para. 6.2.12).

In carriage motion

Defective right
carriage stop
switch

Replace stop switch
assembly (Para. 6.2.11 ).

Defective or
disconnected
printhead cable

Check cable connections.
Replace if defective
(Para. 6.2.5).

Defective
printhead

Replace printhead
(Para. 6.2.4).

Defective PCB

Replace PCB (Para.
6.2.6).

self-test, carriage
moves to home
position and stops.
Printhead does not
fire in print
self-test mode;
carriage moves.

S-3

Table 5-1

Troubleshooting Checklist (Cont)

Symptom

Probable Cause

Remedy

Characters have
dots missing.

Printhead cable
not seated or
is broken.

Check connections. If
broken, replace cable
(Para. 6.2.5).

Defective
printhead

Replace printhead
(Para. 6.2.4).

Defective PCB

Replace PCB (Para.
6.2.6).

No printout in
print self-test
mode; carriage
moves and
printhead sounds
as if it is
firing.

Paper thickness
lever is
misadjusted.

Readjust paper thickness
lever.

Defective ribbon
cartridge

Replace ribbon cartridge.

Print head
operates, but
carriage does
not move. (Isolate
fault with
carriage motion
self-test.)

Defective PCB

Replace PCB (Para.
6.2.6).

Carriage wire
snagged or broken.
Defective
carriage
transistor
assembly
Defective
carriage motor

Replace wire if broken
(Para. 6.2.14).
Replace defective
transistor assembly
(Para. 6.2.15).
Replace motor if
defective (Para.
6.2.15).

Characters
missing or
incorrect (always
the same
character).

Defective PCB

Replace PCB (Para.
6.2.6).

Characters not
spaced evenly.
(Isolate fault
with carriage
motion self-test.)

Defective
carriage
transistor
assembly

Replace defective
transistor assembly
(Para. 6.2.15).

Defective
carriage motor
Carriage wire
is snagged or
tension
incorrect

Replace motor if
defective (Para.
6.2.15).
Replace wire if broken
(Para. 6.2.14).

Defective PCB

Replace PCB (Para.
6.2.6).
5-4

Table 5-1

Troubleshooting Checklist (Cont)

Symptom

Probable Cause

Remedy

Paper jams.

Printhead not
fully seated

Make sure printhead is
seated properly.

Paper path
obstructed

Clear paper path.

Paper thickness
lever
misadjusted

Adjust paper thickness
lever.

Tractors (for
pinfeed paper)
misadjusted
or defective

Adjust tractors. If
defective, replace
tractors (Para.
6.2.13).

Paper path
obstructed

Clear paper path.

Defective line
feed motor

Replace line feed motor
(Para. 6.2.16).

Defective tractor
mechanism

Replace tractors
(Para. 6.2.13).

Printhead too
far from paper

Adjust paper thickness
lever.

Defective ribbon
cartridge

Replace ribbon cartridge.

Defective ribbon
cartridge

Replace ribbon cartridge.

Ribbon wire
slipping or
broken

Replace ribbon wire
(Para. 6. 2.10).

Defective
change-gear arm

Replace change-gear
arm (Para. 6.2.9).

Defective ribbon
cartridge

Replace ribbon cartridge.

Worn platen

Replace platen (Para.
6.2.8).

Defective PCB

Replace PCB (Para.
6.2.6).

Print lines
overlapping.

Light print

Print light
(ribbon not
advancing).

Print density
varies across
page.

5-5

Table 5-1 Troubleshooting Checklist (Cont)
Symptom

Probable Cause

Remedy

Printout
incorrect.
Communication
problems
(Isolate fault
with loopback
self-test).

Faulty
communication
cable

Replace cable.

Configuration
switches set
incorrectly

Check switch positions
(Para. 6.2.6).

Defective PCB

Replace PCB (Para.
6.2.6).

5-6

CHAPTER6
SERVICING

6.1 GENERAL
This chapter explains how to remove and install the printer mechanical and electrical subassemblies. Figure
6-1 shows the assembly removal sequence. The chapter also includes lubrication requirements and
procedures.

ACCESS
COVER

PAPER
BAIL

RIBBON
CARTRIDGE

PCB
COVER

PRINTHEAD
CABLE

PRINTHEAD

PCB

TOP
COVER

CARTRIDGE
MOUNTING
PLATE

CARRIAGE
WIRE

__[

.l.

RIBBON
WIRE

POWER
TRANS._
SWITCH,NOISE
FILTER

CARRIAGE
MOTOR

CARRIAGE
TRANSISTOR
ASSEMBLY

LINE
FEED
MOTOR

CHANGEGEAR

ARM

FRONT PANEL
AND RIGHT
CARRIAGE
STOP SWITCH
ASSY-RA, RD

BOTTOM
COVER

5V
TRANSISTOR

PCB
FUSES

PLATEN

PAPER-OUT,
COVER
INTERLOCK,
AND
CARRIAGE
SENSOR
SWITCH
ASSY-RA,RD

TRACTOR
ASSEMBLY

FRONT PANEL.
RIGHT
CARRIAGE
STOP SWITCH
AND COVER
INTERLOCK
SWITCH
ASSY-RB, RC

POWER
CORD

AC LI NE
FUSE
MA-10,400A

Figure 6-1

Assembly Removal Sequence
6-1

6.2 REMOVAL AND REPLACEMENT PROCEDURES
The following paragraphs describe the removal and replacement procedures.
6.2.1 Printer Housing
Perform the following procedures to remove and replace the printer housing.
Top Cover
WARNING
Set the power switch to 0 and disconnect the ac
power cord.
1.

Remove the paper and access covers (Figure 6-2).

Locate the slot in the platen knob (Figure 6-3). While prying at the slot with a small screwdriver,
pull off the platen knob.

Remove two screws at the ends inside the front of the top cover and two screws at the rear of the
bottom cover.

Press in the carriage stop switch side tabs (Figure 6-4). Pull the switch out of its holder. Guide
the switch wires through the slot in the holder.

Unplug the panel connector from the PCB (Figure 6-5).

Unplug the ground clip from the top cover (Figure 6-6).

Replace the top cover by reversing the above procedure.

MA-10,386A

Figure 6-2

Paper and Access Covers

MA-10,385A

Figure 6-3

6-2

Cover Housing

MA-10,387E

.
Figure 6-4 Carriage Stop Switch

6-3

GROUND WIRES

NOISE FILTER

MA-10,387F

Figure 6-5 Panel Connector

6-4

MA-10,3858

Figure 6-6 Indicator and Switch Assembly

6-5

Bottom Cover

NOTE
The power transformer, power switch, noise filter,
and fuse plate are removed as an assembly with the
bottom cover.
1.

Remove the top cover.

Set the printer on its back side (Figure 6-7). Use a cushion to protect the printer from scratches.

Remove the four screws from the PCB cover and remove the cover.

Remove the screw holding the PCB at the bottom left corner.

Set the printer on its feet.

Remove the ground wires attached to the left side of the mechanism (Figure 6-5).

Remove the two screws from the noise filter (Figure 6-5).

Remove the four screws holding the mechanism to the bottom cover.

Lift the mechanism and remove the power transformer connector (J9) from the PCB (Figure
6-8).

l 0.

Remove the bottom cover.

11.

Install the cover by reversing the above procedure.

MA-10,3848

Figure 6-7 Bottom Cover

6-6

CARRIAGE
TRANSISTOR
ASSEMBLY

DJB~

~/--~\
7

_ 1J - 7

/
INTERFACE

FUSE FU1

COVER INTERLOCK (RA),
PAPER-OUT AND
CARRIAGE SENSOR SWITCH

POWER
TRANSFORMER

FUSE FU2

MA-10,395A

Figure 6-8

Printed Circuit Board Connector
and Fuse Locations

6.2.2 Operating Voltage Setup
Printer model RA and RD can operate at either 100 or 120 volts. Model RB and RC can operate at either
220 or 240 volts. The label on the fuse plate at the rear of the printer shows the operating voltage. The plug
mating of the power supply connector determines the operating voltage of the printer. Perform this procedure to check the connector plug mating and to make a change if necessary.
1.

Set the power switch to 0 and disconnect the ac power cord.

Remove the top cover (Paragraph 6.2.1 ).

Remove the two screws from the noise filter (Figure 6-5) and remove the filter to access the
power supply connector (Figure 6-9).

Check the plug mating of the connector. If you need to make a change, unplug the connector,
rotate one end, and replug the ends. Figure 6-9 shows the connector voltage settings. For example, for the LASO-RA, the desired setting should read SET FOR 120 V AC.

Return the connector and noise filter to their original locations.

Replace the top cover.

6-7

POWER SUPPLY

CONNECTOR SHOWN IN POSITION FOR
MODEL LA50-RA

UNPLUG, ROTATE
AND REPLUG FOR
100 VAC. (LA50-RD)

---,
SET FOR

120VAC

___ J

---,
NOT SET
FOR

100 VAC
___ JI

OTHER SIDE OF ABOVE CONNECTOR

CONNECTOR SHOWN IN POSITION FOR
MODEL LA50-RB

---,
SET FOR

UNPLUG, ROTATE
AND REPLUG FOR
240 VAC. (LA50-RC)

220 VAC
___ J I

---...,I
NOT SET
FOR

240 VAC
I

___ J

OTHER SIDE OF ABOVE CONNECTOR
MA-10,397A

Figure 6-9 Power Supply Connector

6-8

6.2.3 Fuse Replacement
The following paragraphs describe removing and replacing fuses.
AC Line Fuse
WARNING
Set the power switch to 0 and disconnect the ac
power cord.
1.

Turn the fuse holder counterclockwise until it is free (Figure 6-10).

Pull out the fuse holder and remove the fuse.

Replace the fuse and holder by reversing the above procedure.
CAUTION
Replace the fuse with a fuse of equal value.

FUSE RETAINER
MA·10,026

Figure 6-10 AC Line Fuse

6-9

PCB Fuses
1.

Remove the top cover (Paragraph 6.2.1 ).

Turn the printer so the rear faces you.

The fuses are located on the right side of the PCB (Figure 6-11). Replace the blown fuse.

Replace the top cover.

MA-10,385C

Figure 6-11

PCB Fuses

6-10

6.2.4 Printhead
Perform the following procedure to remove and replace the printhead.
WARNING
If the printer was used recently, the printhead may
be hot. Be careful when handling.
Set the power switch to 0 and disconnect the ac
power cord.
1.

Remove the access cover (Figure 6-12). Move the carriage to the approximate center of the
printer mechanism away from the paper bail rollers.

Remove the ribbon cartridge.

Release the printhead clamps in the direction of the arrows shown in Figure 6-12.

MA-10,388A

Figure 6-12

Printhead Clamps

6-11

Pull the head upward, carefully avoiding the paper bail bar (Figure 6-13 ).

Replace the printhead by reversing the above procedure.

6.2.5 Printhead Cable
Perform the following procedure to remove and replace the printhead cable.
WARNING
Set the power switch to 0 and disconnect the ac
power cord.
I.

Remove the access cover (Figure 6-2).

Remove the printhead (Paragraph 6.2.4).

Move the carriage to the right side.

Remove one screw from the hold-down clip and remove the clip (Figure 6-14).

Remove the screw holding the ground lead.

Unplug the cable from the PCB.

Remove the two screws holding the printhead plug.

Remove the cable assembly.

Replace the printhead cable by reversing the above procedure.

Figure 6-13

Printhead Removal

6-12

MA·10,394A

Figure 6-14 Printhead Cable

6-13

6.2.6 PCB Assembly
Perform the following procedure to remove and replace the PCB assembly.
NOTE
The PCB also contains the power supply.
WARNING
Set the power switch to 0 and disconnect the ac
power cord.
CAUTION
Static electricity damages MOS components. Do not
touch MOS pins.
1.

Remove the paper and access covers (Figure 6-2).

Set the printer on its back (Figure 6-7). Use a cushion to protect the printer from scratches.

Remove the four screws from the PCB cover and remove the cover.

Remove the four screws from the PCB.

Disconnect the eight connectors (Figure 6-8) and the grounding wire.

Remove the PCB.

Replace the PCB by reversing the above procedure.

Run the Print Self-Test (Paragraph 3.2.3). Each succeeding line of characters should print
directly below the previous line (Figure 3-2). If necessary, adjust potentiometer VR2 ALIGN
(Figure 6-15) to move the lines. (VR 1 is a factory adjustment and is not a field adjustment.)

6.2. 7 Paper Bail
Perform the following procedure to remove and replace the paper bail.
1.

Remove the access cover (Figure 6-2).

Remove the two E-rings that hold the paper bail bar (Figure 6-16).

Remove the paper bail bar.

Replace the paper bail by reversing the above procedure.

6-14

COVER

ADJUSTMENT
COVER INTERLOCK
BRACKET-RA*

* SWITCH SHOWN IS
USED ON RA MODEL PRINTER
MA-10,387C

Figure 6-15

Print Adjustments

ACCESS
COVER

E RING
MA-10,392A

Figure 6-16 Paper Bail

6-15

6.2.8 Platen
Perform the following procedure to remove and replace the platen.
1.

Remove the top cover (Paragraph 6.2.1 ).

Remove the printhead (Paragraph 6.2.4).

Remove the screw holding the platen on the right side (Figure 6-17). The screw is reached
through a hole in paper feed gear C. An alternate method is to remove gear C first. An E-ring
holds the gear in place.

Remove the screw holding the platen on the left side.

Pull the bail bar away from the platen.

Remove the paper feed gear D. An E-ring holds the gear in place.

MA-10,391A

Figure 6-1 7 Pia ten

6-16

Remove the right and left screws that hold the paper guide.

Remove the platen and paper guide at the same time.

Replace the platen by reversing the above procedure.

6.2.9 Change-Gear Arm
Perform the following procedure to remove and replace the change-gear arm.
l.

Remove top cover (Paragraph 6.2.1 ).

Remove the printhead (Paragraph 6.2.4).

Remove the four screws holding the cartridge mounting plate (Figure 6-18 ).

Remove the cartridge mounting plate slowly to avoid losing the ratchet spring and ribbon spring.

CARTRIDGE
DRIVE
GEAR

SPRING

RIBBON
WIRE
HOLDER

MA~10,389A

Figure 6-18 Carriage Assembly
6-17

Remove the cartridge drive gear and ratchet gears with springs by pulling upward.

Remove the screw holding the change-gear arm. Remove the arm.

Replace the assembly by reversing the above procedure.

6.2.10 Ribbon Wire
Perform the following procedure to remove and replace the ribbon wire.
I.

Remove the change-gear arm (Paragraph 6.2.9).

Remove the screw from the ribbon wire holder (Figure 6-19).

Remove the ribbon wire from the wire holder, ribbon wire arm, and the ribbon pulley gear. Note
the position of the wire on the ribbon pulley gear for reinstallation. Place the wire from the
ribbon wire arm over the wire from the wire holder (Figure 6-19).

Replace the ribbon wire by reversing the above procedure.

RIBBON PULLEY

GEAR
MA-10,396

Figure 6-19

Ribbon Wire

6-18

6.2.11

Front Panel and Carriage Stop Switch Assembly - RA, RD/ Front Panel, Carriage Stop
Switch, and Access Cover Interlock Switch Assembly - RB, RC
Perform the following procedure to remove and replace the front panel and carriage stop switch assembly
and, if the printer is a model RB or RC, the cover interlock switch.
1.

Remove the top cover (Paragraph 6.2.1).

Remove the six screws holding the indicator and switch assembly to the front panel (Figure 6-6).

For model RB or RC, remove the screw holding the cover interlock switch to the top cover
(Figure 6-20).

Replace the assembly by reversing the above procedure.

Figure 6-20

Cover Interlock - Model RB,RC

6-19

6.2.12 Paper-Out, Access Cover Interlock and Carriage Sensor Switch Assembly-RA, RD/
Paper-Out and Carriage Sensor Switch Assembly - RB, RC
Perform the following procedure to remove and replace the paper-out, access cover interlock, and carriage
sensor switch assembly.
WARNING
Set the power switch to 0 and disconnect the ac
power cord.
1.

Remove the PCB (Paragraph 6.2.6).

Remove the top cover (Paragraph 6.2.1).

Remove the screw from the power switch cover (Figure 6-15).

Remove the two screws from the noise filter.

Remove the ground wires on the left of the mechanism.

Remove the four screws holding the mechanism to the bottom cover. Remove the printer
mechanism.

Cut the switch assembly cable ties.

Remove the two screws from the paper-out switch and the screw from the carriage sensor
switch.

For model RA or RD, remove the screw from the cover interlock bracket on the side of the
mechanism.

l 0.

Remove the switch assembly from the printer mechanism. Guide the paper-out switch lever
from its slot.

11.

Replace the assembly by reversing the above procedure.*

12.

Run the Print Self-Test (Paragraph 3.2.3). The first character of the line should line up with the
red etch mark on the bail bar. If necessary, adjust the carriage sensor switch (Figure 6-15) to
change the line position.
NOTE
If the carriage sensor switch is set too far to the left,
the carriage will jam to the left side.

* Apply Locktite 241 or equivalent to the paper-out and carriage sensor switch screws. Locktite 241 is a
tradename for Thomas and Betts Co.

6-20

6.2.13 Tractor Assembly
Perform the following procedure to remove and replace the tractor assembly.

Remove top cover (Paragraph 6.2.1 ).

Remove the two screws from the paper-out switch (Figure 6-15).

Remove the two screws holding the tractor shaft (Figure 6-21).

Remove the E-ring from the tractor drive gear.

Remove the drive gear from the tractor drive shaft.

Remove the E-ring from the other side of the drive shaft.

Remove the tractor assembly.

Replace the tractor assembly by reversing the above procedure.

TRACTOR
DRIVE GEAR
MA-10,390A

Figure 6-21

Tractor Assembly

6-21

6.2.14 Carriage Wire
Perform the following procedure to remove and replace the carriage wire.
l.

Remove the top cover (Pargraph 6.2. l).

Remove the printhead (Paragraph 6.2.4).

Remove the ribbon wire (Paragraph 6.2.10).

Loosen the tension arm screw (Figure 6-22).

MA-10,387H

Figure 6-22 Carriage Drive Assembly

6-22

Remove the screw holding the drive pulley on the motor and pull up on the pulley to remove it
(Figure 6-23).

Remove the carriage wire from the pulley.

Remove the screws on each end of the carriage guide shaft and pull the shaft toward you (Figure
6-22).

Swing the carriage assembly upward.

Remove the wire retainer nut under the carriage and remove the wire (Figure 6-24).

DRIVE PULLEY

MA-0387-82

Figure 6-23

Carriage Motor

WIRE NUT

CARRIAGE
UNDERSIDE

Figure 6-24 Carriage Retainer

6-23

Perform the following procedure to reasemble the carriage wire.

Connect the wire under the carriage with the retainer nut. Apply Locktite 241 or equivalent to
the threads before tightening the nut.*

Position the carriage to the approximate center and reconnect the guide shaft.

Insert the longer end of the carriage wire into the drive pulley's lower hole and position the
pulley on the motor shaft (Figure 6-25).

Pass the wire through the tension arm (Figure 6-22), and turn the drive pulley clockwise until the
wire is tight.

Insert the other end of the wire in the upper hole of the pulley and tighten the pulley screw.

Hold the pulley in place and wind the wire on the pulley in the clockwise direction.

Put the wire on the tension arm pulley.

Push the carriage to one side and use a scale and tension gauge (Figure 6-26) to check the
tension.

Push the center of the wire in IO mm. The gauge should read 500 grams± 20 grams.

10.

Adjust the tension arm screw to change the tension. Tighten the screw to slacken the tension.
Loosen the screw to increase the tension.

<F
I

MA-0389·82

Figure 6-25

Carriage Wire Installation

* Locktite 241 is a tradename for Thomas and Betts Co.

6-24

WIRE

MOTOR PULLEY
TENSION PULLEY

SCALE

TENSION GAUGE

MA-0390-82

Figure 6-26 Carriage Wire Tension Adjustment

6.2.15 Carriage Motor
Perform the following procedure to remove and replace the carriage motor.
1.

Remove the printer housing (Paragraph 6.2.1).

Loosen the ribbon wire arm screw and remove the wire from the arm (Figure 6-18). Temporarily
hook the wire on the cartridge mounting plate to avoid dislocating it from the ribbon pulley gear.

Remove the screw from the drive pulley and remove the pulley (Figure 6-23). Keep the wires in
place on the pulley.

Remove the three screws holding the motor and remove the motor in a downward direction.

Install the motor by reversing the above steps.

Push the carriage to one side and use a scale and tension gauge (Figure 6-26) to check the
tension.

Push the center of the wire in 10 mm. The gauge should read 500 grams± 20 grams.

Adjust the tension arm screw to change the tension. Tighten the screw to slacken the tension.
Loosen the screw to increase the tension.

6-25

6.2.16 Line Feed Motor
Perform the following procedure to remove and replace the line feed motor.
l.

Remove the printer housing (Paragraph 6.2.1 ).

Remove the platen (Paragraph 6.2.8).

Remove the tractor assembly (Paragraph 6.2.13).

Remove the two screws holding the paper thickness lever (Figure 6-27).

Loosen the carriage wire tension arm and remove the wire. (Refer to reassembly instructions of
Paragraph 6.2. l 4 for tension adjustments.)

Loosen the ribbon wire holder and remove~ the wire.

MA-10,391C

Figure 6-27

Line Feed Motor Replacement

6-26

Remove the gears on the right side of the mechanism.

Remove the nine screws holding the right side of the mechanism.

Remove the two screws holding the line feed motor and remove the motor.

10.

Install the motor by reversing the above procedure.

NOTES
The paper thickness lever adjusts the gap between
the printhead and the platen in four increments of
0.1 + 0.05 mm. The gap is adjustable from 0.5 +
0.05 mm to a maximum of 0.8 + 0.05 mm. Figure
6-28 shows the lever positions for the gap settings. If
the paper thickness lever was disassembled, perform
the following readjustment procedure.
1.

Loosen the screw that holds the two parts of the
lever.

Adjust part A of the lever for a 0.5 mm gap
between the printhead and the platen.

Position part B of the lever on the 0.5 mm
indent (Figure 6-28).

Tighten the screw.

6.2.17 Power Transformer, Power Switch, and Noise Filter
Perform the following procedure to remove and replace the power transformer, power switch, and the noise
filter.
1.

Remove the printer housing (Paragraph 6.2.1).

Unplug the power supply connector (Figure 6-9).

CAUTION
The power requirements of each model of the LASO
printer are specific. The label on the fuse plate indicates the voltage setting. When reconnecting the
power supply connector, refer to Paragraph 6.2.2
for proper orientation of the connector.
3.

Remove the two screws holding the transformer to the bottom cover. Remove the transformer.

Unplug the connector between the noise filter (Figure 6-15) and the fuse plate. Remove the
noise filter and power switch.

Install the assembly by reversing the above procedure.

6-27

MA-0433-82

Figure 6-28

Paper Thickness Lever

6-28

6.2.18 5 V Transistor or Carriage Transistor Assembly
Perform the following procedure to remove and replace the 5 V transistor or carriage transistor assembly.
1.

Remove the bottom cover (Paragraph 6.2.1).

Remove the PCB (Paragraph 6.2.6).

Remove the screw(s) holding the transistor(s) to the mechanism frame and remove the transistor
or transistor assembly (Figure 6-29).

Replace the transistor(s) by reversing the above procedure.

Apply heat conducting paste under the transistor(s) and Locktite 241 * or equivalent to the
screw(s).

CARRIAGE
TRANSISTOR
ASSEMBLY

MA-0432-82

Figure 6-29

5 V Transistor and Carriage Transistor Assembly

* Locktite 241 is a tradename for Thomas and Betts Co.
6-29

6.3 LUBRICATION
The LASO printer is lubricated at the factory. The printer requires lubrication at scheduled inspections and
when major repairs are performed. Before lubrication, clean the parts of old oil, rust inhibitors, dust, and
dirt. Apply new lubrication sparingly. Wipe off excessive oil.

Table 6-1 is a lubrication guide listing the parts location, intervals, and type of lube. Refer to Table A-1 for
the part numbers. Figure 6-30 shows the lubrication locations. The locations on the figure are keyed to
those in the table.

Table 6-1

Lubrication Guide

This table is keyed to Figure 6-30. Refer to this figure for the location codes.
Location

Part(s)

Interval

Type of Lube

Platen bushings

Overhaul

Mollub-Alloy
No. 00

Tractor drive
shaft bearings

Overhaul

Mollub-Alloy
No.00

Paper feed gear
shafts-Band D

Overhaul

Mollub-Alloy
No.00

Carriage tension
arm shaft

Overhaul

Mollub-Alloy
No. 00

Carriage guide
shaft

Overhaul

Essa Beacon
No. 325

Carriage shaft
rmg

Inspection and
overhaul

Launa #40

6-30

DRIVES~AFT

TRACTOR

BEARV)NG

O'C

~'~"''°

TENSION ARM

CARRIAGE
GUIDE SHAFT
MA-0391-82

Figure 6-30

Lubrication Locations

6-31

APPENDIX A
PARTS LIST

Table A-1 is the parts list for the LASO printer.

Table A-1

Parts List

Description

Part Number

LASO-RA (whole unit)*
LASO-RB (whole unit)*
LASO-RC (whole unit)*
LASO-RD (whole unit)*
Printhead*
Printhead cable
Printhead circuit board (PCB)
Front panel and carriage stop assembly - RA, RD
Front panel, carriage stop switch, and
access cover interlock switch assembly - RB, RC
Paper-out, access cover interlock, and
carriage sensor switch assembly - RA, RD
Paper-out, and carriage sensor switch assembly - RB, RC
Power transformer, power switch and noise filter assembly - RA, RD
- RB, RC

30-198S8-01
30-198S 8-02
30-198S8-03
30-1985 8-04
29-24272-00
29-24258-00
29-24238-00
29-24283-00
29-24284-00

Power switch - RA,RD
Power switch - RB,RC

5 V transistor
Carriage transistor assembly
Paper bail bar
Platen
Platen knob
Paper thickness lever
Paper release lever
Release lever shaft
Pinch roller
Ribbon guide
Ribbon wire
Ribbon wire arm
Ribbon wire holder
Tractor assembly
Tractor drive gear
Tractor (left)

A-1

29-24282-00
29-2428S-OO
29-24239-00
29-24240-00
29-24280-00
29-24233-00
29-24264-00
29-24247-00
29-24263-00
29-242S2-00
29-24278-00
29-24248-00
29-24271-00
29-24268-00
29-24269-00
29-24273-00
29-24277-00
29-24260-00
29-242SO-OO
29-2426S-OO
29-24270-00
29-24266-00

Table A-1

Parts List (Cont)

Description

Part Number

Tractor (right)
Carriage motor
Carriage wire
Tension arm
Tension arm pulley
Carriage motor drive pulley
Carriage motor guide shaft bearing
Carriage stop
Carriage guide shaft
Carriage shaft
Carriage mechanism assembly
Cartridge mounting plate
Lubrication ring
Change-gear arm
Line feed motor
Paper feed gear (B)
Paper feed gear ( C)
Paper feed gear (D)
Top cover
Bottom cover
Access cover - RA,RD
Access cover - RB,RC
Paper cover
Control panel
Rubber foot
LASO screws kit
LASO E-ring kit
LASO spring kit
Lube, Launa No. 40
Lube, Mollub-alloy No. 00
Lube, Esso Beacon No. 32S
AC line fuse reg-blo, 2A, 2SO V - RA
AC line fuse T type, 1A, 250 V - RB
PCB fuse FUl, 3.lSA, 250 V
PCB fuse FU2, SA, 2SO V
Fuse holder, 3AG - RA
Fuse holder, S X 20 mm - RB
EIA loopback connector*

29-24267-00
29-242S3-00
29-24246-00
29-24244-00
29-2424S-OO
29-242S7-00
29-242Sl-OO
29-24262-00
29-242S9-00
29-24261-00
29-2427S-OO
29-24274-00
29-24249-00
29-24276-00
29-242S4-00
29-242S6-00
29-24243-00
29-242SS-00
29-24241-00
29-24279-00
29-24236-00
29-24237-00
29-2423S-00
29-24234-00
29-24281-00
29-24230-00
29-24231-00
29-24232-00
29-24S78-00
29-24S79-00
29-24S80-00
90-0721S-OO
12-19283-00
12-19284-05
12-19284-07
12-18848-02
12-18848-03
12-1 S336-01

Power Cables
United States
Australia
Continental Europe
United Kingdom
Switzerland
Denmark

17-00083-09
17-00198-00
17-00199-00
17-00209-00
17-00210-00
17-00310-01

*CD Kit

A-2

APPENDIXB
ESCAPE SEQUENCE
AND SWITCH SUMMARY

Escape Sequence Summary
Name/Mnemonic

Escape Sequence /Description

Set horizontal pitch
DECSHORP

ESC
033
Pn=

[
133
0
10

ESC
033
Pn=

[
133
0
6

Page length selection
DECSLPP

ESC
033

[
133

Pn= 0 to 252

Pn (Jines/page)= Paper length (inches/page)
X Vertical pitch (Jines/inch)

Partial line down
PLO

ESC
033

K
113

Move down 1/2 line (paper up
1/12inch)

Partial line up
PLU

ESC
033

L
114

Move up 1/2 line (paper down
l/12inch)

Select density
DECDEN

[
ESC
133
033
Pn= 0, 1
Pn= 2

Select graphic
rendition
SGR

[
; ........ Pn
ESC
Pn
***
133 *** 073
033
Pn= 0-Reset
Pn= 1 - Bold on
Pn= 4 - Underline on

Set vertical pitch
DECVERP

***

w
167

1
10

I 1~ I

z
172
2
8

***

1
6

I I

t
164

***

5
1!.51 5

6
6

8
8.25 CPI

4
2

5
3

6
4LPI

3
12

z
"
042
172
Select normal density printing
Select enhanced density printing
Pn

***

B-1

m
155
Pn = 22 - Bold off
Pn = 24 - Underline off

Escape Sequence Summary (Cont)
Name/Mnemonic

Escape Sequence /Description

Device attribute
DA

[
c
ESC
133
143
033
Sends back identification code
[
?
1
7
ESC
133 077
061
067
033
ESC
033
ESC
033
ESC
033

[
133
[
133
[
133

ESC
033

[
133

Brief status report
(sent back by
printer) DSR

ESC
033
ESC
033

Extended status
reports (sent back
by printer) DSR

Device status request
DSR

n
156
?

1
061
2
061

n
156
n
156

077

3
063

n
156

[
133
[
133

0
060
3
063

n
156
n
156

[
ESC
133
033
followed by
[
ESC
133
033
[
ESC
133
033
followed by
[
ESC
133
033

0
060

n
156

?
077
3
063

2
062
n
156

0
060

077

***

,...
073

077
?

c
143
Send extended status
report
Disable all unsolicited
status reports
Enable unsolicited brief
reports and send extended
status report
Enable unsolicited
extended report and send
extended status report
No malfunction detected
Malfunction detected

No malfunction detected

n
156
Malfunction detected

***

Pn = 21 Hardware failure
Pn = 22 Communication failure (event)
Pn = 23 Input buffer overflow (event)
Pn = 24 Printer deselected
Pn = 26 Cover open
Pn = 27 Paper empty
Enter graphics mode

ESC P
q
Enter graphics mode
033
120
161
! n Repeat introducer, n = 0 to 65535
$ Graphic carriage return
- Graphic new line

Exit graphics mode

ESC
033

\
134

B-2

Pn
156

Character Set Selection
SO
CTRL/N (016)
SI
CTRL/O (017)
SS2 ESCN(033116)
SS3 ESC 0 (033 117)
LS2 ESC n (033 156)
LS3 ESC o (033 157)
LSlR ESC,..., (033 176)
LS2R ESC I (033 175)
LS3R ESC I (033 174)

Select GO to be GL
Select G 1 to be GL
Select next character from G 2
Select next character from G 3
Select G2 to be GL
Select G3 to be GL
Select G 1 to be GR
Select G2 to be GR
Select G3 to be GR

Assign Character Sets
ESC Gn ch
Assign set ch to Gn where Gn is
"("=GO
")" =

"*" = G2

"+" = G3

and ch is from the list below
B-ASCII
A - Britain
5 - Finland*
C- Finland
R - France
9 - French Canada*
Q - French Canada
K-Germany
Y - Italy

J -JIS Roman
I - JIS Katakana
6 - Norway /Denmark*
E - Norway /Denmark
Z-Spain
7 -Sweden*
H-Sweden
< - Multinational
0 - VTlOO Graphics

* preferred

Country
US (ASCII)
Britain
Finland
France
French Canada
Germany
Italy
Japan
Norway /Denmark
Spain
Sweden

Switch Bank 1
Switch
4
2
3

0
0

0
0
0
0
0

c
c
c
c

c
c
c

0
0

c
c

0
0

c
c

0
0
0

0
0

c
0
c
0
c
0
c
0
c
0

0 =OPEN: C =CLOSED

NOTES
1.

For all countries except Japan:
GO = Selected country,
Gt= VTlOO,
G2 =Multinational, and
G3=ASCII

B-3

For Japan:
GO = JIS Roman,
Gt= Katakana,
G2 =Katakana, and
G3 =ASCII

Switch Bank 2
Switch
2
3
1

Baud Rate

0
0
0

4800
2400
1200
600
300
200

c
c

0
0

110

c
c
c
c

Data Format

Switch Bank 2
Switch
4
5
6

0
0

c
c

7 Bits+ odd parity
7 Bits+ even parity
7 Bits + 8th bit mark
7 Bits+ 8th bit space
8 Bits + odd parity
8 Bits+ even parity
8 Bits + no parity

c
0
c
0
c
0

c
c

c
0
c

0
0

c
c
c
c

0
0
0

c
c

0 =OPEN: C =CLOSED
Switch Bank 1
Aspect Ratio

(Switch 5)

Protocol Switch

(Switch 6)

2:1
2:5.1

XON/XOFF
Ready/Busy

Signal Level

(Switch 7)

Right Margin

(Switch 8)

Busy= High:
Ready= Low
Busy= Low:
Ready= High
Power-Up Conditions

Truncated

Wrap

Printer selected
Printer status report
Horizontal pitch
Vertical pitch
Page length
Active position
Bold, underline, double width
Printing density
7-bit mode
8-bit mode

on-line
disable unsolicited report
10 characters/inch
6 lines/inch
11 inches
top leftmost position

off
normal
GL=GO
GL=GO;
GR=G2

Character sets, aspect ratio, protocol, right margin, and data format are selected per switch settings.

B-4

Vertical Pitch (Characters/Inch)

16.5

8.25

Enhanced
Bold
Underline

x
x
x

x
x

x
x
x

Maximum characters/line

132

Attributes

B-5

APPENDIXC

GLOSSARY

Al5:AO

Sixteen-line microprocessor address bus

AD7:ADO

Eight-line multiplexed address/data bus

ALE

Address lines enable

ANSI

American National Standards Institute

ASCII

American Standards Committee for Information Interchange

Asynchronous

For serial data transmission, method allowing sender and receiver to operate with nonidentical clocks

Baud rate

Rate of data exchange on a serial interface

Bus

A group of wires carrying many separate but related signals

Byte

Eight bits considered as a unit

CPU

Central processing unit

DSR

Data set ready

DTR

Data terminal ready

EIA

Electronic Industries Association - refers to the EIA standard 1/0 interface, RS-232-C

ESC

Escape character (ASCII 1B16/033g)

Escape character

A control character that provides code extention and is a prefix affecting
the interpretation of a limited number of contiguous characters

Escape sequence

A sequence of characters that performs a control function

Firmware

Microprocessor program (microprogram)

Flag

External signal to the microprocessor

C-1

Full-duplex

Communications system capable of transmitting data m two different
directions at the same time

Host

Computer that the printer communicates with

INTR

Interrupt

A signal to the microprocessor to set aside its current work to take care of
a high priority task. Such tasks include getting data from a communication line before it disappears

10/M

Input/ output/(not)memory

LED

Light emitting diode

Mark

One of two states of a communication line, usually defined as a low signal
level or the presence of current flow (see also space)

Matrix

An arrangement that allows addressing of many discrete points with few
address lines

On-line

When the printer receives its data from the host computer

Parallel

Data path where all bits travel on separate wires at the same time

Parser

A firmware process that separates a sequence of characters into its component parts

RAM

Random access memory

Read

Receive only

ROM

Read only memory

Routine

A set of instructions to the microprocessor that makes it perform a specific
function

RS-232-C

An EIA standard that dictates data interface characteristics

RTS

Request to send

RxD

Receive data - USART

RxRDY

Receiver ready - USART

Serial

Transmission of data bit-by-bit over a single data line

Space

One of two states of a communication line, usually defined as a high signal
level or the absence of current (see also mark)

C-2

Start bit

The first bit in serial asynchronous byte transmission - always a space

Stop bit

The last bit (or bits) in serial asynchronous byte transmission - always a
mark

Vector

The address of the first instruction for an interrupt handling routine

Write

Wake-Up

XOFF

Control character that asks the sender to stop sending

XON

Control character that asks the sender to resume sending

C-3

APPENDIXD
SPECIFICATIONS

Operating Characteristics

Printing technique

Impact dot matrix

Print method

Incremental with bidirectional lookahead

Characters

94 ASCII
81 Multinational
6 3 JTS Katakana
27 VTIOO Special Graphics
1 error indicator

Character features

Enhanced density
Bold
Underlined
Doublewidth

Print density

7 by 9 matrix (normal)
13 by 9 matrix (enhanced)

Graphic mode

144 or 180 dots/inch horizontal
72 dots/inch vertical
2: 1 or 2.5: 1 aspect ratio

Print speed

100 characters per second
(7 by 9 matrix printing)
44 lines per minute (80
characters per line)

Line feed speed

100 milliseconds/line at 6
lines/inch

D-1

Character pitch
Compressed font

16. S characters per inch, 13 2
characters/line
8.2S characters per inch, 66
characters/line
12 characters per inch, 96
characters/line
6 characters per inch, 48
characters/line
10 characters per inch, 80
characters/line
S characters per inch, 40
characters /line

Double width
Elite pitch
Double width
Pica pitch
Double width

Line spacing

12, 8, 6, 4, 3, or 2 lines/inch
Partial line up and down, 1/12
inch

Paper feed

Sprocket-feed, tractor drive
Friction-feed, platen drive

Paper dimensions

Single sheets: 3 to 9 inches wide
Sprocket paper: 4.S to 10 inches wide
Sprocket holes: 4 to 9.S inches on center
O.SO ± 0.01 inch spacing

Paper thickness

0.011 inches maximum
(original plus 3 sheets)

Ribbon

Disposable cartridge
Two million characters !ife expectancy
(average use)

Power Requirements
Model
Printer

Nominal

Operating Range

Vac

Major Market
Area

LASO-RA
LASO-RB
LASO-RC
LASO-RD

120
220
240
100

116 ± 10%
213 ± 10%
232 ± 10%
100 ± 10%

U.S. and Canada
Mainland Europe
United Kingdom
Japan

Frequency range

47 to 63 Hz

Power consumption

Operating: 180 watts maximum
Idling: 16 watts

Data interface serial RS232-C and RS423 EIA standard

D-2

Physical Characteristics

Weight

8.5 Kg (18.7 lb)

Dimensions
Width
Depth
Height

400 mm (16 in)
295 mm (11.8 in)
142 mm (5.6 in)

Environment
Temperature
Relative humidity

10° C to 40° C
50° F to 104° F
10% to 90%

D-3

Reader's Comments

LASO PRINTER TECHNICAL MANUAL

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The Documentation Products Directory and the DECdirect Guide contain information on the
remainder of DIG IT A L's technical documentation.
Copies of the above Directory and Guide, as well as additional copies of this document, are
available by writing or calling:
Digital Equipment Corporation
Accessories and Supplies Group
P.O. Box CS2008
Nashua, New Hampshire 03061
Attention: Documentation Products
Telephone: 1-800-258-1710
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