OKIDATA ML172 Series User manual

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Service Guide ML172/ML182 Series
Chapter 0 About This Manual
ML172/ML182 Series
Dot Matrix Printers
Adobe Acrobat printable reference
copy of the OKIDATA Service Training Manual.
09/17/97
Note: This Adobe Acrobat version of the Okidata Service Training Manual was built with the
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Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Table of Contents Page
Service Guide ML172/ML182 Series
0 About This Manual
Front Cover 1
Copyright 2
1 General Description & Specifications
1.1 General Description 3
....1.1.1 ML172 4
....1.1.2 ML182 5
....1.1.3 ML182-PLUS 6
....1.1.4 ML182-TURBO 7
1.2 Specifications 8
2 Principles of Operation
2.1 Electrical Principles Of Operation 9
....2.1.1 Power Supply 10
....2.1.2 Control PCB 11
....2.1.3 Interconnect Board 12
....2.1.4 Operator Board 13
2.2 Mechanical Principles Of Operation : Printhead 14
....2.2.2 Head Gap Adjusting Mechanism 15
....2.2.3 Space Mechanism / Operation 16
....2.2.4 Ribbon Feed Mechanism / Operation 17
....2.2.5 Paper Feed Mechanism / Operation 18
....2.2.6 Paper-end Detection Mechanism 19
....2..2.7 Semi-Automatic Sheet Feed (SASF) 20
3 Printer Maintenance
3.1 General Information 21
....Figure 3-1a - ML172 22
....Figure 3-1b - ML182 23
....Figure 3-1c - ML182-PLUS/ML182-TURBO 24
3.2 Maintenance Procedures 25
....3.2.1 Upper Cover 26
....3.2.2 Control Board 27
....3.2.3 Transformer Assembly 28
....3.2.4 Power Supply Board 29
....3.2.5 Operation Board 30
....3.2.6 Printhead 31
....3.2.7 Ribbon Feed Gear Assembly 32
....3.2.8 Space Motor Assembly 33
....3.2.9 Space Rack 34
....3.2.10 Carriage Cable 35
....3.2.11 Printer Mechanism 36
....3.2.12 Linefeed Motor Assembly 37
....3.2.13 Column Indicator Bar 38

Table of Contents Page
....3.2.14 Platen Assembly 39
....3.2.15 Interconnect Board 40
....3.2.16 Paper Chute Assembly 41
....3.2.17 Bottom Paper Guide Assembly 42
....3.2.18 Near-end Lever And Bracket 43
....3.2.19 Bottom Near-end Lever 44
3.3 Adjustments 45
....3.3.2 Space Rack and Roller Gap Adjustment 46
3.4 Printer Self-Tests 47
3.5 Preventive Maintenance 48
4 Interfacing Techniques
4.1 Interfacing Techniques 49
5 Failure Analysis Procedures
5.1 Failure Analysis Procedure 50
....RAP Index 51
........Board layout and Wiring - ML182Plus and ML182Turbo 52
........Board layout and Wiring - ML172 and ML182 53
........Pin Numbers and Signals 54
........Check Points for Printed Circut Boards - 172 55
........Check Points for Printed Circuit Boards - ML182 56
........Check Points for Printed Circuit Boards - ML182Plus and
ML182Turbo 57
........RAP #1: Power is on but carriage does not move 58
........RAP #2: Power LED lights, but the carriage does not
move 59
........RAP #3: Carriage movement is abnormal when power is
turned on 60
........RAP #4: Homing operation is normal, but the indicators
(LED1 to LED9) are abnormal when power is turned on. 61
........RAP #5: Fuse F1 on power supply board (SLPB) blows
when power is turned on. 62
........RAP #6: Fuse F1 on the control board blows when power
is turned on. 63
........RAP #7: Neither spacing nor printing performed while
receiving data. 64
........RAP #8: Spacing is normal, but nothing is printed while
receiving data. 65
........RAP #9: Printer stops printing. 66
........RAP #10: Wrong characters are printed or some
characters are missing. 67
........RAP #11: Some dots are missing. 68
........RAP #12: Print is light. 69
........RAP #13: Line feed is not performed. 70
........RAP #14: Fuse F1 on power supply board blows while
receiving data and printing. 71

Table of Contents Page
........RAP #15: Switch on the operator panel does not work
(Carriage returns to home position when power is turned on). 72
........RAP #16: Paper not fed properly (SASF function). 73
A PCB Referance Charts
Power Supply Board (SLPB) 74
ML172 Control Board (SLMR-51 & SLMR-52) and Operator
Board 75
ML182 Control Board (SLMC) 76
ML182 Control Board (SLMR) and Operator Board 77
ML182-PLUS & ML182-TURBO Control Board (SLMX) and
Operator Boards 78
A PCB Reference Charts
RS232-D Super Speed Serial I/F Board 79
B Parts Compatability Chart
Parts Compatability Chart 80

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Service Guide ML172/ML182 Series
Chapter 0 About This Manual
Copyright
All rights reserved. No part of this document may be reproduced in any form without the prior written
permission of OKIDATA.
Every effort has been made to ensure that the information in this document is complete, accurate and up
to date. We do not assume responsibility for errors beyond our control.
© Copyright 1989 by OKIDATA
First Edition May 1989
CENTRONICS is a registered trademark of Centronics Inc.
EPSON is a registered trademark of Seiko Epson Corporation
OKIDATA and MICROLINE are registered trademark of Oki America Inc.
IBM is a registered trademark of International Business Machines, Inc.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

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Service Guide ML172/ML182 Series
Chapter 1 General Description & Specifications
1.1 GENERAL DESCRIPTION
The Microline 172, 182, 182-PLUS and 182-TURBO Printers are reliable, compact, dot matrix printers
using a 9-wire printhead. These printers use a re-inking cartridge ribbon.
Although these printers are similar in appearance, there are differences in the features that each printer
offers. Lets take a closer look at each printer.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 4
Service Guide ML172/ML182 Series
Chapter 1 General Description & Specifications
1.1.1 ML172
Emulates the IBM Graphics Printer.

Pitch, page length and print mode are set through a MENU.

Switches on the Control Board select default Menu settings. Settings return to default values when

the printer is powered off.
Pull tractor is standard.

Available in two models:

1. Centronics parallel interface, this model will not accept a serial board.
2. RS232-D serial interface. This model can be configured for parallel operation by removing the
Serial Board from the Control Board.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 5
Service Guide ML172/ML182 Series
Chapter 1 General Description & Specifications
1.1.2 ML182
Two models are available, IBM emulation, or Microline emulation.

Available with two interfaces, Centronics Parallel, or RS232-C Serial (9600 Baud, Ready Busy

Protocol). An optional Super Speed Serial board (19.2 Baud, Ready Busy and X-On, X-Off
Protocols) is available.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 6
Service Guide ML172/ML182 Series
Chapter 1 General Description & Specifications
1.1.3 ML182-PLUS
The ML182-PLUS is an enhanced version of the ML182, with the following features:
Push-button front panel which allow the setting of Pitch (10,12 or 17 CPI), and Mode (Near Letter

Quality, Utility and High Speed Draft).
SASF (Semi-Automatic Sheet Feed), which allows single sheets of paper to be automatically loaded

using the bail arm lever.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 7
Service Guide ML172/ML182 Series
Chapter 1 General Description & Specifications
1.1.4 ML182-TURBO
The ML182-Turbo is a faster version of the ML182-PLUS, but does not provide SASF capability. Print
speed at 10 CPI is 155 CPS in Utility mode, and 186 CPS in HSD mode. Super Speed Draft at 232 CPS is
available at 12 CPI.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 8
Service Guide ML172/ML182 Series
Chapter 1 General Description & Specifications
1.2 SPECIFICATIONS
1.2.1 Paper-end Detection
· Paper-end is detected when the end of the paper is about 1 inch from the printing position.
1.2.2 Input Power
· 120 VAC +/- 10% 50/60 Hz +/- 2%
· 220 VAC +/- 10% 50/60 Hz +/- 2%
· 240 VAC +/- 10% 50/60 Hz +/- 2%
1.2.3 Ribbon
· Type: Re-Inking Cartridge
· Ribbon Life: Approximately 3 million characters
1.2.4 Line Feed Selection
· 6 lpi (.167 inch)
· 8 lpi (.125 inch)
· n/72 inch
· n/144 inch (Microline emulation)
· n/216 inch (IBM emulation)
NOTE: Refer to your Printer Handbook for applicability to your specific printer model.
1.2.5 Number Of Copies
· Original plus three copies (16 to 20 lb. weight paper)
NOTE: The ML172 is capable of printing an original plus two copies
1.2.6 Paper Feed Methods
· Bottom Feed
· Rear Feed
· Top feed (single sheets)
· Semi-Automatic Sheet Feeder (SASF) - ML182-Plus only
1.2.7 Print Speed
· ML172, ML182, ML182-PLUS
1 - Applies to ML172 & ML182-PLUS only
· ML182-TURBO

1.2.8 Reliability
· Printhead Life: Approximately 200 million characters
· MTBF: 4000 hours @ 25% duty cycle/35% page density
· MTTR: 15 minutes @ major sub-assembly level
1.2.9 Available Options
· Tractor Feed Assembly 1
· Super-speed Serial Interface (RS232-C)
· Roll Paper Stand
1 - Standard on the ML172
2 - Not available for ML172
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 9
Service Guide ML172/ML182 Series
Chapter 2 Principles of Operation
2.1 ELECTRICAL PRINCIPLES OF OPERATION
The printers major electrical assemblies are shown in Figure 2-1.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 10
Service Guide ML172/ML182 Series
Chapter 2 Principles of Operation
2.1.1 Power Supply
The Power Supply consists of the power supply board and the transformer. The Power Supply Board,
which contains the ON/OFF Switch, Line Filter and related circuits, uses a 1 amp fuse for over-current
protection. This circuit board transforms the AC input voltage into 7.6 VAC, 24 VAC and 10 VAC for use
on the Control PCB. The Transformer contains a thermal fuse for protection against overheating. If the
thermal fuse opens, the transformer must be replaced.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 11
Service Guide ML172/ML182 Series
Chapter 2 Principles of Operation
2.1.2 Control PCB
The Control PCB contains the microprocessor and related circuits, DC power circuit, motor drive circuits,
paper end sensor and interface connector(s). If a serial interface is installed, it will be connected to the
Control PCB. The DC power circuit converts the AC input from the power supply board into +8 VDC, +5
VDC and +30 VDC to be used throughout the printer.
The Control PCB also contains the following two protective circuits:
a) Driver Fault - Alarm Circuit
This circuit causes the AC fuse (on the power supply board) to open when a fault occurs in the printhead
drive circuit, linefeed motor drive circuit or the spacemotor drive circuit. If the drive time of any drive circuit
exceeds a pre-determined time, an alarm condition will exist as follows:
HDALM - Printhead drive circuit alarm

SPALM - Spacemotor drive circuit alarm

LFALM - Linefeed motor drive circuit alarm

When any of the above signals become active, the Driver Fault - Alarm Circuit will output the ALM signal.
This signal then turns ON an SCR (which is located on the Control Board). When the SCR turns ON, the
secondary winding (30V) of the transformer is short-circuited. This induces an over-current condition
through the primary winding of the transformer causing the AC fuse (F1) to open.
b) Head Overheat - Alarm Circuit
In order to protect the printhead coils, this circuit monitors the head temperature using the printheads
built-in thermistor. When the temperature of the printhead exceeds 100 degrees Celsius, a head overheat
alarm (HEAD TEMP) is generated. This alarm causes the printing operation to stop until the printhead
cools. Once the printhead temperature returns below the alarm detection threshold, the printing operation
is restarted.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 12
Service Guide ML172/ML182 Series
Chapter 2 Principles of Operation
2.1.3 Interconnect Board
The Interconnect Board is nothing more than a BUS, used to connect the printhead, operator panel,
spacemotor, linefeed motor and semi-automatic sheet feeder (SASF) Switch (ML182 PLUS only) to the
Control PCB.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 13
Service Guide ML172/ML182 Series
Chapter 2 Principles of Operation
2.1.4 Operator Board
The Operator Board contains switches and indicators which allow the printer operator to control and
monitor the printers operation. The ML172 and ML182 use the same type Operator Board (SLSQ) while
the ML182-PLUS and ML182-TURBO use the same type Operator Board (SLSX). For specific information
on the capabilities and use of each of these Boards, please refer to the appropriate Printer Handbook.
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

Page: 14
Service Guide ML172/ML182 Series
Chapter 2 Principles of Operation
2.2 MECHANICAL PRINCIPLES OF OPERATION : Printhead
The Printhead used by the ML172, ML182, ML182-PLUS and ML182-TURBO is a highly efficient Stored
Energy type. Power is not consumed until a printwire is activated, thereby extending the printhead life to
approximately 200 million characters.
The printhead is designed with nine (9) vertically aligned wires. Each wire is welded to an armature ring.
Behind this armature ring is a spacer ring.
Each of the nine print wire armatures on the ring has a permanent magnet behind it. The magnets attract
the armatures, keeping the print wires inside the printhead. Because of the spacer ring behind the
armature ring, the armature is attracted toward the permanent magnet at a cocked angle. There is also a
coiled wire, wrapped around each of the nine permanent magnets.
When a dot is to be printed, current passes through the coiled wire, creating a magnetic field which
counters the magnetic field of the permanent magnet. This causes the armature and print wire to spring
forward and imprint a dot onto the paper.
When the current is removed from the coiled wire, the magnetic field of the permanent magnet attracts the
armature, causing the print wire to retract into the printhead.
This printhead contains a built-in thermistor (rated at 100 degrees Celsius) to monitor the head
temperature. When the printhead temperature exceeds the 100 degree setting, the thermistor generates
an output signal to the Control PCB.
The printer then stops printing and sends a BUSY signal to the host computer. Data remains in the print
buffer until the printhead temperature is below 100 degrees Celsius. At this time, the BUSY signal to the
host computer becomes inactive and printing is resumed.

Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)