Oki ML520 User Manual

Download

Page: 1

Service Guide ML520/521

Chapter 0 About This Manual

ML520 // ML521

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

pictures rendered at 300 dpi, which is ideal for printing, but does not view on most displays well.

Table of Contents Page

Service Guide ML520/521

0 About This Manual

Front Cover 1 Copyright Information 2

1 Product Specifications

1.1.01 General Information 3

....1.2 Physical Specifications 4

....1.3 Power Requirements 5

....1.4 Environmental Conditions 6

....1.5 Agency Approvals 7

....1.6 Operational Specifications 8

....1.7 Paper Specifications 9

....1.8 Memory Specifications 10

....1.9 Consumables 11

....1.10 Options - Cut Sheet Feeders 12

........1.10.02 Pull Tractor Kit 13

........1.10.04 Bottom Push Tractor Kit 14

........1.10.05 Serial Interface 15

........1.10.06 Roll Paper Stand 16

........1.10.08 OKISmart Typer Utility 17

....1.11 Reliability 18

2 Principles of Operation

2.1 Electrical Operation 19

....2.1.01 Main Control Board 20

........Block Diagram 21

........Program ROM 22

........RAM 23

........LSI 24

........Electrically Erasable Programmable Read Only Memory

(EEPROM)

....2.1.02 Initialization 26

....2.1.03 Parallel Interface Control 27

....2.1.04 Print Control 28

........LSI/Printhead Interface 29

........Gap Adjust Control 30

........Print Compensation Control 31

....2.1.05 Space and Line Feed (SP/LF) Motor Control 32

........Line Feed Motor Control 33

........Space Motor Control 34

........Encoder Disk 35

....2.1.06 Operation Panel 36

....2.1.07 Alarm Circuit 37

........Low Motor Drive Voltage Alarm 38

Table of Contents Page

........Head Drive Time 39

........Print Speed 40

........%Head Overheat Alarm Processing 41

....2.1.08 Power Supply Circuit 42

2.2 Mechanical Operation - Printhead Mechanism 43

........Printhead Gap Information 44

........Interconnect Diagram: Control Board to Printhead 45

........Line Feed Motor Resistance 46

........Space Motor Resistance 47

........Printhead Operation 48

........Printhead Temperature 49

....2.2.02 Spacing Mechanism 50

........Spacing Operation 51

....2.2.03 Head Gap Mechanism 52

........Ribbon Drive Operation 53

....2.2.05 Line Feed Mechanism 54

........Cut Sheet/Continuous Sheet Switching Mechanism 55

........Cut Sheet Paper Feed Operation 56

........Continuous Paper Feed (Rear Tractor Mechanism) 57

........Continuous Paper Feed (Pull Tractor Mechanism) 58

........Continuous Paper Feed (Bottom Tractor Feed

Mechanism)

........Continuous Paper Feed (Push/Pull Tractor Mechanism) 60

....2.2.06 Paper Detection Mechanism 61

....2.2.07 Support Protector Mechanism 62

....2.2.08 Automatic Paper Load 63

........Continuous Feed Paper 64

....2.2.09 Paper Park 65

3 Maintenance & Disassembly

....3.1.01 General Information 66

....3.1.02 Maintenance Tools 67

....3.1.03 Maintenance Precautions 68

3.2 Disassembly/Assembly Procedures 69

....3.2.01 Preliminary Items 70

....3.2.02 Printhead Assembly 71

....3.2.03 Ribbon Protector 72

....3.2.04 Gear Case Assembly 73

....3.2.05 Pull-up Roller Assembly 74

....3.2.06 Upper Cover, Access Cover, and Sheet Guide

Assemblies

....3.2.07 Control Board (FJIM) 76

....3.2.08 Power Supply Assembly 77

....3.2.09 Operator Panel PCB (LEOP) 78

....3.2.10 PC Connector 79

Table of Contents Page

....3.2.11 Space Motor and Roller Guide Assemblies 80

....3.2.12 Carriage Cable 81

....3.2.13 Space Rack 82

....3.2.14 Roller/Holder Backup Assembly 83

....3.2.15 Guide Rail and Adjust Cam 84

....3.2.16 Left Ground Plate 85

....3.2.17 Right Ground Plate 86

....3.2.18 Rear and Cut Sheet Paper Feed Sensor Levers 87

....3.2.19 Platen Assembly 88

....3.2.20 Paper Chute Assembly 89

....3.2.21 Line Feed Motor Assembly 90

....3.2.22 Reset Spring 91

....3.2.23 Idle Gear and Change Lever 92

....3.2.24 Pressure Spring 93

....3.2.25 Carriage Shaft 94

....3.2.26 Leaf Spring 95

....3.2.27 Bottom Paper Sensor Levers 96

....3.2.28 Front Pressure Roller Assembly 97

....3.2.29 Tractor Assembly 98

....3.2.30 Main Frame 99

3.3 Printer Adjustments 100

....3.3.02 Printhead Gap Adjustment 101

....3.3.03 Key Combinations 102

....3.3.04 Menu Operation 103

........Menu Settings 104

....3.3.05 Top of Form 105

....3.3.06 Paper Park 106

....3.3.07 Tear Feature 107

....3.3.08 Forms Tear Off 108

....3.3.09 Resets 109

3.4 Cleaning 110

3.5 Lubrication 111

3.6 Shipping Instructions 112

4 Failure & Repair Analysis

....4.1.01 Introduction 113

....4.1.02 Printer Serial Number Identification 114

....4.1.03 Firmware Revision Identification 115

4.2 Reporting Problems - General Information 116

....4.2.02 Problem Lists 117

....4.2.03 Reporting Methods 118

4.3 Troubleshooting Updates 119

4.4 Troubleshooting Tips 120

....4.4.02 Problem Categories 121

....4.4.03 START HERE Flowchart 122

Table of Contents Page

....4.4.04 Tips for Preventing Image Problems 123

....4.4.05 Common Problems 124

4.5 Abnormal Output - Output Samples 125

....Left Margin Drifting Problem 126

4.6 Fault Alarms 127

....4.6.02 ALARM/LED Display Troubleshooting Table Index 128

....4.6.03 ALARM/LED Display Troubleshooting Tables 129

4.7 Repair Analysis Procedures (Raps) 130

....4.7.02 RAP Index 131

........RAP 01 No Power Supplied to Printer 132

........RAP 02 No Spacing Operation 133

........RAP 03 Printhead Homing Error 134

........RAP 04 Paper Jam During Paper Loading 135

........RAP 05 Printhead Pins Not Firing 136

........RAP 06 Poor Print Quality 137

........RAP 07 Ribbon Feed Problem 138

........RAP 08 Line Feed Problem 139

........RAP 09 Operation Panel Malfunction 140

........RAP 10 Parallel Interface Problem 141

........RAP 11 Serial Interface Problem 142

4.8 Printer Tests 143

....4.8.02 Rolling ASCII Test 144

....4.8.03 Font Test 145

....4.8.04 Serial Interface Loopback Test 146

........Serial Cable Information 147

........Serial Interface Signal Requirements 148

........Commonly Used Serial Cable Configurations 149

....4.8.05 Hexadecimal Dump Mode 150

4.9 Resistance Checks 151

........Layout Diagram 152

....4.9.02 Printhead 153

....4.9.03 Line Feed Motor Resistance 154

....4.9.04 Space Motor Resistance 155

A Reference Charts

A.1 Overview - A.1.01 General Information 156 A.2 Index To Charts 157

........Board Layout 158

....A.2.01 Main Controller Board (FJIM) 159

....A.2.02 Operator Panel Board (LEOP) 160

....A.2.03 Power Supply Assembly 161

....A.2.04 Space Motor Board 162

....A.2.05 RS232-C Serial Interface Board - Option (LXHI) 163

B Illustrated Parts Listing

B.1 Overview - B.1.01 General Information 164

Table of Contents Page

........Format 165

........Current Part Numbers 166

....B.1.02 Definition of Terms 167

....B.1.03 Parts Ordering Information 168

B.2 Charts 169

........Overview 170

....B.2.01 Printer 171

....B.2.02 Upper Cover Assembly 172

....B.2.03 Printer General Assembly 173

....B.2.04 Printer Unit 174

....B.2.05 Printer Unit 175

....B.2.06 Printer Unit 176

....B.2.07 Carriage Assembly 177

....B.2.08 Options 178

....B.2.09 Option Parts 179

....B.2.10 Consumables 180

....B.2.11 Packing Materials 181

....B.2.12 Documentation 182

....B.2.13 Service Training Kit Revision List 183

Service Guide ML520/521

Chapter 0 About This Manual

This document may not be reproduced without the written permission of the Okidata Technical Training Group. Every effort has been made to ensure the accuracy of the information contained in this training course. Okidata is not responsible for errors beyond its control.

© 1994 by Okidata All rights reserved. First Edition February, 1993 P/N 59257801 Second Edition September, 1993 P/N 59257802 Third Edition December, 1994 P/N 59257803 Written and produced by the Okidata Technical Training Group Please address any comments on this publication to: Technical Training Group

Page: 2

Okidata 532 Fellowship Road Mount Laurel, NJ 08054-3499 Fax Number: (609) 235-2600, ext. 7034 Okilink Login Name: Technical Training OKIDATA is a registered trademark of Oki Electric Industry Company, Ltd.; marques deposee de

Oki Electric Industry Company, Ltd.; marca registrada, Oki Electric Industry Company, Ltd. MICROLINE is a registered trademark of Oki Electric Industry Company, Ltd.; marque depose de

Oki Electric Industry Company, Ltd. OkiSmart Paper Handling is a trademark of Oki Electric Industry Company, Inc. PLUG n PRINT is a registered trademark of Oki America, Inc.; marque deposee de Oki America,

Inc. Bitstream is a registered trademark of Bitstream Incorporated. Epson is a registered trademark of Seiko Epson Corporation. IBM is a registered trademark of International Business Machine Corporation. MS-DOS is a registered trademark of Microsoft Corporation. PC is a registered trademark of International Business Machine Corporation.

Proprinter is a registered trademark of International Business Machine Corporation. Windows is a trademark of Microsoft Corporation

Page: 3

Service Guide ML520/521

Chapter 1 Product Specifications

1.1.01 General Information

The Microline 520 and Microline 521 are letter quality, nine-pin, dot-matrix printers which utilize

OKISMART

adjustment. The printer actually reads and learns the print medium being used, then automatically adjusts the head gap to the optimum distance. This autogapping process leads to longer printhead life.

Options include the Bottom Feed Push Tractor, Cut-Sheet Feeder, Pull Tractor and Serial Interface Board. The Microline 520 is an 80 column printer.

The Microline 521 is a 132 column printer. Okidata's one year limited warranty covers the parts, labor and printhead on both printers.

The following items are available for the printer.

paper handling. Patented Okidata technology does away with the manual head gap

OKISMART Typer

typewriter on checks, labels and envelopes.

OKISMART Panel

computer. Scalable Fonts - 14 scalable fonts, available on diskette.

- software which provides the flexibility for the Microline 590/521 to function like a

- a utility program that lets you control selected printer functions from your personal

NOTE:

The OkiSmart software includes three programs.

1. OkiSmart Control

2. OkiSmart Panel Emulator

3. OkiSmart Setup Refer to the Printer Handbook for more information.

Service Guide ML520/521

Chapter 1 Product Specifications

1.2 PHYSICAL SPECIFICATIONS

1.2.01 Dimensions

NOTE:

Dimensions INCLUDE the platen knob, acoustic cover, and paper separator.

Microline 520

Width: 16.9 inches (43 centimeters) Depth: 14.9 inches (37.8 centimeters) Height: 6.5 inches (16.5 centimeters)

Microline 521

Width: 23 inches (58.4 centimeters) Depth: 14.9 inches (37.8 centimeters) Height: 6.5 inches (16.5 centimeters)

1.2.02 Printer Weight

Page: 4

Microline 520

17.6 pounds (8.0 kilograms)

Microline 521

23.1 pounds (10.5 kilograms)

1.3 POWER REQUIREMENTS

1.3.01 Input Power

120 VAC: +5.5 / -15% 230/240 VAC: +10 / -14%

1.3.02 Power Consumption

Operating: 110 VA Idle: 40 VA Local Test: 70 VA

1.3.03 Power Frequency

120 VAC: 60 Hz +/- 2% 230/240 VAC: 50/60 Hz +/- 2%

Page: 5

Service Guide ML520/521

Chapter 1 Product Specifications

1.4 ENVIRONMENTAL CONDITIONS

1.4.01 Acoustic Rating

Near Letter Quality Mode Microline 520 54.9 dBA Microline 521 54.4 dBA Utility Mode Microline 520 57.2 dBA Microline 521 56.9 dBA Quiet Mode

Page: 6

Service Guide ML520/521

Chapter 1 Product Specifications

Microline 520 52.5 dBA Microline 521 52.3 dBA

1.4.01 Altitude

10,000 feet (3,050 meters)

1.4.03 Ambient Temperature and Relative Humidity (RH)

While operating: 41 to 104 degrees Fahrenheit (5 to 40 degrees Celsius) Operating humidity: 20% to 80% RH While in storage: 14 to 122 degrees Fahrenheit ( - 10 to 50 degrees Celsius) Storage humidity: 5% to 95% RH

1.5 AGENCY APPROVALS

1.5.01 Listings

UL No: UL Standard No. 1950 D3 CSA No: CSA Standard 22.2-950 D3 FCC: FCC Certified per Part 15, Subject J, Class B IEC: IEC 950 VDE: VDE 0805 VDE 0875 Class B BS: BS 7002

Page: 7

Service Guide ML520/521

Chapter 1 Product Specifications

Service Guide ML520/521

Chapter 1 Product Specifications

1.6 OPERATIONAL SPECIFICATIONS

1.6.01 Character Matrix Sizes

Table of Print Speed and Character Matrix

Mode Speed 80 (12cpi) 320 (12cpi) 427 (12cpi) Matrix (H x V) 17 x 13 9 x 7 7 x 7

Print Speed at Different CPI for the ML 520/521

Near Letter Quality Utility High Speed Draft

Page: 8

Mode HSD

Utility

CPI CPS Horiz. DPI Vert. DPI IPS

10 427 90 72 42.7 12 427 108 72 35.6 15 427 135 72 28.5

17.1 427 154 72 25.0 20 427 180 72 21.4 10 320 120 72 32 12 320 144 72 26.7 15 320 180 72 21.3

17.1 320 206 72 18.6 20 320 240 72 16.0 10 80 240 144 16.0 12 80 288 144 13.3 15 80 360 144 13.3

17.1 80 412 144 9.32 20 80 480 144 8.0

1.6.02 Characters Per Line Microline 520

Characters Per Line Characters Per Inch

80 10

96 12 120 15 137 17.1 160 20

Microline 521

Characters Per Line Characters Per Inch

136 10 163 12 204 15 233 17.1 272 20

1.6.03 Character Pitches

5, 6, 8.5, 10, 12, 15, 17.1, 20

1.6.04 Character Sets

Standard ASCII EPSON Character Set I & II IBM Character Set I, II & All Characters Foreign Character Substitution International Character Sets Code Page 850, 860, 863, 865 and 437 Line Graphics Bar Code Code 39 UPC A UPC E EAN 8 EAN 13 Interleaved 2 of 5 Code 128 (A, B, C) Postnet

1.6.05 Emulations

NOTE: The emulations are co-resident

Epson FX IBM Proprinter Microline Standard

1.6.06 Fonts

Near Letter Quality

Courier

Utility

Gothic

High Speed Draft

Gothic

Bar Code

Code 39 UPC A UPC E EAN 8 EAN 13 Interleaved 2 of 5 Code 128 (A, B, C) Postnet

1.6.07 Front Panel Switches

SELECT / Menu Micro Feed Up / Down Shift Paper Park Line Feed Pitch Selection FORM FEED / Load Print Quality Selection Top of Form Tear Quiet Reset

1.6.08 Graphics Resolution

Graphics Resolution: 288 (horizontal) x 144 (vertical) dots per inch (DPI) maximum

1.6.09 Interface

Standard

Centronics Parallel

Optional

RS232C Serial

1.6.10 Line Feed Increments

Fixed

6 lines per inch (lpi) [0.167 inch (4.23 millimeters)] 8 lines per inch (lpi) [0.125 inch (3.175 millimeters)]

Variable

n/60 inch n/72 inch n/144 inch n/216 inch

1.6.11 Line Feed Time

65 milliseconds 6 lines per inch (lpi) 6 milliseconds 8 lines per inch (lpi) 1 second 5.0 inches (Continuous paper feed rate)

1.6.12 Menu Mode Switch Action

Paper park Prints the entire menu.

Line Feed / Reverse Selects Group Function

FORM FEED / Load Selects Item

Tear Selects Item Value

SEL / Menu Exits Menu Mode, Enters Select

1.6.13 Paper Feed Methods

Standard

Friction Feed (Top) Rear Push Tractor (Rear)

Optional

Pull Tractor (Bottom) Bottom Push Tractor Feed (Bottom) Single-Bin Cut Sheet Feeder (Top) CSF 5000 - Narrow CSF 5001 - Wide

1.6.14 Paper Feed Paths

Top Feed (Standard) Rear Feed (Standard) Bottom Feed (by using an Optional feed mechanism) Special Features

Paper Park Automatic Paper Loading Forms Tear Off

1.6.15 Paper Loading

Auto Loading (Top Feed) Press FORM FEED / Load switch to feed paper to default position

1.6.16 Paper Out Detection

Distance from end of paper Rear Feed: 0.5 inches (12.7 mm) Bottom Feed: 0.5 inches (12.7 mm) Top Feed: 0.5 inches (12.7 mm)

1.6.17 Paper Tear Capabilities

Forms Tear-0ff (sharp edge on access cover) Metal Tear Bar (with optional bottom feed tractor unit)

1.6.18 Print Method

Printhead Type

General Information

Impact: Dot Matrix 9 pin printhead .0134 inch (0.34 millimeter) diameter pins

Overheat Protection

When printhead temperature exceeds 110 degrees Celsius, the printer stops bi-directional printing. Uni-directional printing begins.

If the temperature exceeds 118 degrees Celsius, printing stops. Printing will resume when the printhead temperature drops below 118 degrees Celsius.

NOTE:

Refer to Section Two for more information on printhead operation.

Printhead Gap Information

Three items factor into printhead gap information:

1. Printhead Gap Adjustment

This is a SERVICE ADJUSTMENT made by a technician. It is covered in Section 3.3 of this Service Handbook. The Adjustment measures 0.014 +/- 0.001 inches 90.35, +/-0.03 mm).

2. Printhead Gap Adjustment

This is a MENU ITEM in the SET-UP Group. It fine tunes the automatic setting of the printhead gap. The settings are 0, 1 and -1. Use 1 to darken print (if output is consistently light). Use -1 to lighten print (if output is consistently dark).

3. Gap Control

This is a MENU ITEM in each (Paper Feed) Group. The Groups are REAR FEED, BOTTOM FEED, and TOP FEED. Gap Controls determines how the printhead gap is set. The settings are listed below.

An explanation of each setting follows.

Auto Gap

printing.

Semi Auto Gap

job is printing.

Auto Gap, Semi Auto Gap, 1, 2, 3, 4, 5, 6, 7, 8, 9

This is the factory default. Automatically determines paper thickness of the first page. During single-sheet feed, each page's thickness is checked while a job is

Similar to Auto Gap. Automatically determines paper thickness of the first page. During single-sheet feed, each page's thickness IS NOT checked "while" a

1, 2, 3, 4, 5, 6, 7, 8, 9

Used when the same paper is used ALL of the time. Bypasses the automatic head gap adjustment. 1 is the narrowest head setting. 9 is the widest head setting.

1.6.19 Print Modes

Near Letter Quality Utility High Speed Draft

1.6.20 Print Speed

Table of Print Speed and Character Matrix

Mode

Speed 80 (12 cpi) 320 (12 cpi) 427 (12 cpi)

Matrix (H x V) 17 x 13 9 x 7 7 x 7

Near Letter Quality Utility High Speed Draft

Service Guide ML520/521

Chapter 1 Product Specifications

1.7 PAPER SPECIFICATIONS

CAUTION:

Use Bottom Feed and/or optional Pull Tractor for card stock and labels.

1.7.01 Types

Card Stock

Weight: 120 lbs. (450 g/m 2 ) Maximum Width: Microline 520 5 to 8 inches (12.7 to 20.3 centimeters)

Microline 521 5 to 14 inches (12.7 to 35.6 centimeters) Length: 3 to 17 inches (7.62 to 43.18 centimeters) Thickness: .017 inches (0.44 millimeters)

Page: 9

Paper Feed Path: Bottom Printhead Gap Information:

Continuous Form

Weight: Single Part 12 - 24 lb. (45 to 90 g/m 2 ) Multi-Part, Carbonless 9 - 11 lb. (35 to 40 g/m 2 ) Multi-Part, Interleaf Paper 10 - 12 lb. (38 to 45 g/m 2 ) Carbon 9 lb. (35 g/m 2 ) Width: Microline 520 3.5 to 10.5 inches (8.8 to 26.6 centimeters) Microline 521 3.5 to 16.5 inches (8.8 to 41.9 centimeters) Length: 3 to 17 inches (7.62 to 43.18 centimeters) Thickness: 0.014 inches (0.36 millimeters) Rear Feed 0.017 inches (0.44 millimeters) Bottom

Feed Paper Feed Path: Rear or Bottom Printhead Gap Information:

Refer to the Printhead Gap Information, Section 1.6

Cut Sheet

Weight: 12 to 24 lbs. (45 to 90 g/m 2 )

Width: 7.2 to 14.3 inches (18.3 to 36.3 centimeters) Width: Microline 520 7.2 to 8.5 inches (18.2 to 21.5 centimeters) Microline 521 7.2 to 14.3 inches (18.2 to 36.3 centimeters) Length: 3 to 17 inches (7.62 to 43.18 centimeters) Thickness: 0.014 inches (0.325 millimeters) Maximum Paper Feed Path: Top Printhead Gap Information: Refer to the Printhead Gap Information, Section 1.6.

Envelopes

Weight: 24 lbs. (90 g/m 2 ) Maximum Size: Single Feed Minimum: 6.5 x 3.6 inches (16.5 x 9.1 centimeters) Maximum: 9.5 x 4.1 inches (24.1 x 10.4 centimeters) Continuous Non-overlap type Thickness: .014 inches (.325 millimeters) Maximum Paper Feed Path: Bottom Printhead Gap Information: Refer to the Printhead Gap Information, Section 1.6.

Labels

Weight: N/A Width: Microline 520 3.5 to 10.5 inches (8.8 to 26.6 centimeters)

Microline 521 3.5 to 16.5 inches (8.8 to 41.9 centimeters) Length: 3 to 17 inches (7.62 to 43.18 centimeters) Thickness: .011 inches (0.28 mm) Maximum (including backing) Paper Feed Path: Bottom Printhead Gap Information: Refer to the Printhead Gap Information, Section 1.6.

CAUTION:

Use Bottom Feed and/or optional Pull Tractor for card stock and labels.

Transparency

NOTE:

Roller marks may mar the transparency under high temperature / high humidity conditions.

Weight: 12 to 24 lbs. (45 to 90 g/m 2 ) Width: Microline 520 7.2 to 8.5 inches (18.2 to 21.5 centimeters)

Microline 521 7.2 to 14.3 inches (18.2 to 36.3 centimeters) Length: 3 to 17 inches (7.62 to 43.18 centimeters) Thickness: 0.14 inches (0.36 millimeters) Paper Feed Path: Top Printhead Gap Information: Refer to the Printhead Gap Information, Section 1.6.

1.7.02 Length

NOTE:

The recommended length is specific to paper type.

Rear Feed Minimum 3 inches (7.62 centimeters) Maximum 17 inches (43.18 centimeters) Bottom Feed Minimum 3 inches (7.62 centimeters) Maximum 17 inches (43.18 centimeters) Top Feed Minimum 3 inches (7.62 centimeters) Maximum 17 inches (43.18 centimeters)

1.7.03 Number of Copies

Original + 4 Interleaf Original + 4 Carbonless Original Cut Sheet

1.7.04 Thickness

0.014 inches / 0.36 mm Maximum Thickness, Rear Feed

0.017 inches / 0.44 mm Maximum Thickness, Bottom Feed

1.7.05 Weight

NOTE:

The recommended weight is specific to paper type.

Minimum: 9 lb. (35 g/m 2 ) Maximum: 120 lb. (90 g/m 2 )

1.7.06 Width

NOTE:

The recommended width is specific to paper type.

Paper

Microline 520 Minimum: 3.5 inches ( 8.8 centimeters) Maximum: 10.5 inches (26.6 centimeters) Microline 521 Minimum: 3.5 inches ( 8.8 centimeters) Maximum: 16.5 inches (41.9 centimeters)

Printing Area

Microline 520 8 inches Maximum Microline 521 13.6 inches Maximum

1.8 MEMORY SPECIFICATIONS

1.8.01 EEPROM

1 Kbit serial EEPROM (used to store Menu data)

1.8.02 EPROM

1 MBit EPROM (Printer Control Program - Fonts)

1.8.03 RAM

128 Kbyte Total Resident RAM

Used as

Receive Buffer Receive Buffer Size is selected through the Menu. Settings are: 64 K, 32 K, 1 line

Page: 10

Service Guide ML520/521

Chapter 1 Product Specifications

Print Buffer DLL Buffer Scratch Pad

Service Guide ML520/521

Chapter 1 Product Specifications

1.9 CONSUMABLES

1.9.01 Ribbon

CAUTION:

Using a non-Okidata ribbon may damage the printhead and void any warranties.

Material

Nylon fabric, cartridge type, re-inking

Type

Black Ribbon

Life (On average, at 10 characters per inch, Utility Mode)

4 million characters

Page: 11

Service Guide ML520/521

Chapter 1 Product Specifications

1.10 OPTIONS - Cut Sheet Feeders

1.10.01 Cut Sheet Feeders

Single Bin

The CSF-5000 is a narrow feeder for the Microline 520.

Single Bin with envelope capability Paper Width: 7.2" to 8.5" (18.3 cm to 36.3 cm) Paper Length: 10.1" to 14" (25.6 cm to 35.6 cm) Capacity: 170 sheets (16 lb.), 100 sheets (20 lb.)

The CSF-5001 is a wide feeder for the Microline 521.

Page: 12

Single Bin with envelope capability Paper Width: 7.2" to 14.3" (18.3 cm to 36.3 cm) Paper Length: 10.1" to 14" (25.6 cm to 35.6 cm) Capacity: 170 sheets (16 lb.), 100 sheets (20 lb.)

Dual Bin

P/N 70022601 is a narrow feeder for the Microline 520.

Dual Bin with envelope capability Paper Width: 7.2" to 8.5" (18.3 cm to 36.3 cm) Paper Length: 10.1" to 14" (25.6 cm to 35.6 cm) Capacity: 170 sheets (16 lb.), 100 sheets (20 lb.)

P/N 70022801 is a wide feeder for the Microline 521.

Dual Bin with envelope capability Paper Width: 7.2" to 14.3" (18.3 cm to 36.3 cm) Paper Length: 10.1" to 14" (25.6 cm to 35.6 cm) Capacity: 170 sheets (16 lb.), 100 sheets (20 lb.)

Service Guide ML520/521

Chapter 1 Product Specifications

1.10.02 Pull Tractor Kit

NOTE:

The Pull Tractor Kit (P/N 70023001) is a narrow feeder for the Microline 520. The Pull Tractor Kit (P/N 70023201) is a wide feeder for the Microline 521.

Bottom Feed Rear Feed (For Push/Pull Operation) Paper Types: Continuous Feed and Labels

Page: 13

Service Guide ML520/521

Chapter 1 Product Specifications

1.10.04 Bottom Push Tractor Kit

NOTE:

The Bottom Push Tractor Kit (P/N 70022901) is a narrow feeder for the Microline 520. The Bottom Push Tractor Kit (P/N 70023101) is a wide feeder for the Microline 521.

Bottom Feed Paper Type: Continuous Feed Includes: Stand and Metal Tear Bar

Page: 14

Page: 15

Service Guide ML520/521

Chapter 1 Product Specifications

1.10.05 Serial Interface

Super-Speed 19.2K RS-232C Ready/Busy/X-On/X-Off Protocols Can be configured through the Menu or OKISmart Utility Program

Service Guide ML520/521

Chapter 1 Product Specifications

1.10.06 Roll Paper Stand

Adapts printer for use with roll-type paper (Model 520 only) Includes: Stand, Support, Cord and DIN plug for connection to printer

Page: 16

Service Guide ML520/521

Chapter 1 Product Specifications

1.10.08 OKISmart Typer Utility

Obtained via BRC (Business Reply Card) packaged with printer Includes: Typewriter Mode, Form Creation Utility and Barcode Utility

1.10.09 OKISmart Panel Utility

Obtained via BRC (Business Reply Card) packaged with printer Includes: Front Panel Control Utility and Drivers for Windows 3.0 & 3.1

NOTE:

The OKISmart software includes three programs.

1. OKISmart Control

2. OKISmart Panel Emulator

Page: 17

3. OKISmart Setup

Refer to the Printer Handbook for more information.

Service Guide ML520/521

Chapter 1 Product Specifications

1.11 RELIABILITY

1.11.01 Mean Time Before Failure (MTBF)

Approximately 6,000 hours: 25% duty cycle / 35% page density

1.11.02 Mean Time To Repair (MTTR)

Approximately 15 minutes to major sub-assembly level

1.11.03 Printer Life

Approximately 16,000 hours of power-on time: 25% duty cycle / 35% page density

1.11.04 Printhead Life

Average 200 million characters in 10 cpi utility mode @ normal 25% duty, 35% page density

Page: 18

1.11.05 Ribbon Life

Approximately 4 million characters

1.11.06 Warranty (Limited)

One year, parts and labor

1.11.07 Service

Authorized OKIDATA Service Centers

Service Guide ML520/521

Chapter 2 Principles of Operation

2.1 ELECTRICAL OPERATION

The printer is comprised of the electrical components listed below.

Main Control Board Power Supply Assembly

Transformer

Filter Board Operator Panel Space Motor / Line Feed Motor Printhead

Page: 19

Page: 20

Service Guide ML520/521

Chapter 2 Principles of Operation

2.1.01 Main Control Board

The main control board is made up of the microprocessor, peripheral circuits, drive circuits, sensors and interface connectors.

The power to the main control board is supplied by the transformer assembly through a wire harness. The power to other electrical parts (line feed motor, space motor and printhead) is provided by the power supply circuitry through connectors on the main control board.

Microprocessor (MPU) (Location 04C: 67X640)

16 bit MPU, using CMOS technology. The MPU contains a 20 bit address bus, a 16 bit data bus. The MPU can access 1 Mbyte of program memory and 1 Mbyte of data memory space. The microprocessor controls the entire printer by executing the control program through the

LSIs and the driver circuits.

Block Diagram

Page: 21

Service Guide ML520/521

Chapter 2 Principles of Operation

Page: 22

Service Guide ML520/521

Chapter 2 Principles of Operation

Program ROM

Location 05CA: 27C1024 This 64k x 16 bit (1Mbit) EPROM contains the control program for the printer. The MPU executes the

instructions contained in this program. The Program ROM is assigned to the program memory area of the MPU and instructions are fetched by

the PSEN signal of the MPU.

Page: 23

Service Guide ML520/521

Chapter 2 Principles of Operation

RAM

Location 05CB: 511664Z The RAM is CMOS dynamic RAM with 65,536 words x 16-bit configuration. It is used as a receive buffer,

print buffer and work buffer.

Page: 24

Service Guide ML520/521

Chapter 2 Principles of Operation

LSI

Location 04B: MSM79VO35 Detects the output of the two-phase sensor on the DC space motor to control the motor drive phase. Transmits and receives serial data to and from the printhead based on the dot timing (which is derived

from the space motor speed). Controls the external interface. The LSI is connected to the MPU.

Page: 25

Service Guide ML520/521

Chapter 2 Principles of Operation

Electrically Erasable Programmable Read Only Memory (EEPROM)

(Location 03C: 93CS46) The EEPROM is a CMOS serial I/O type memory (EEPROM). It is capable of electrically erasing and

writing 1,024 bits. The EEPROM contains the menu data and the head drive time correction data.

Page: 26

Service Guide ML520/521

Chapter 2 Principles of Operation

2.1.02 Initialization

This printer is initialized when the printer is powered on or when the I-PRIME-N signal is input from the host via the parallel interface.

The steps in Printer Initialization are listed below. The RST-N signal is output from the reset circuit to reset the MPU and LSIs. The program is executed and the LSIs are reset by the MPU via IORST-N.

NOTE:

A reset operation initiated by I-PRIME does not reset the MPU.

The program sets the LSI (02D) mode, checks the memory (ROM/RAM), then executes carriage homing and determines the phase of the line feed motor.

Finally, the program establishes the interface signals (P-I/F: ACK-P signal sending, and S-I/F: BUSY-N signal off) and lights the SELECT lamp to indicate that the printer is in the ON-LINE state.

Page: 27

Service Guide ML520/521

Chapter 2 Principles of Operation

2.1.03 Parallel Interface Control

The parallel data input from the host to the interface LSI is latched to the internal register at the falling edge of the STROBE-N signal.

The LSI sets the BUSY-N signal to inform the host that the data is being processed. The LSI also outputs the RXD-N signal to inform the MPU of data reception. The data is read upon receiving the RD-N signal from the MPU.

When the data processing is complete, the BUSY-N signal is disabled and the ACK-N signal is sent to request the next data. When the buffer is full and reception is not desired, the BUSY signal is sent to request data transmission be stopped.

Page: 28

Service Guide ML520/521

Chapter 2 Principles of Operation

2.1.04 Print Control

The print data is transmitted as serial data from the LSI to the control circuit and the driver contained in the printhead.

After the data is printed, the sensor analog circuit controlling each pin returns the pin stroke data to the MPU. The MPU will make an automatic head gap adjustment. This feedback system sets the optimum drive time for each pin in order to maintain high print quality.

In the case of envelopes, where the medium thickness varies as the printhead moves along the platen, the strike force of the pins changes to compensate for the differences in thickness.

Page: 29

Service Guide ML520/521

Chapter 2 Principles of Operation

LSI/Printhead Interface

The connection between the LSI and the printhead is made with the bi-directional serial data bus. The LSI transmits the print data as serial data to the logic circuit of the printhead. The printhead returns serial data from the printhead sensor analog circuit to the LSI. This information is used to determine the optimum drive time for the next print request.

The logic circuit of the printhead signals the LSI if a parity error is detected in the print data.

Page: 30

Service Guide ML520/521

Chapter 2 Principles of Operation

Gap Adjust Control

The Gap Adjust LSI receives stroke length information for all of the printhead pins from the sensor analog circuit. The Gap Adjust LSI then sets the optimum printhead gap for the printing medium.

NOTE:

Refer to Section 2.2.03 for a description of the mechanical process. All values in the below chart are in millimeters

Service Guide ML520/521

Chapter 2 Principles of Operation

Print Compensation Control

The printhead compensates for the shape of the platen as shown below.

NOTE:

Also refer to Section 2.1.07 - Head Drive Time

Page: 31

Page: 32

Service Guide ML520/521

Chapter 2 Principles of Operation

2.1.05 Space and Line Feed (SP/LF) Motor Control

The LSI (Location 04B: MSM79V035) generates the space motor and the line feed motor control signals according to commands received from the MPU. These signals are sent to the SP/LF motor driver.

Page: 33

Service Guide ML520/521

Chapter 2 Principles of Operation

Line Feed Motor Control

The SP/LF motor driver (Location 5A: MHM2025) drives the line feed motor in two-phase bipolar, based on the phase changeover data output from the LSI.

The serial data from the LSI (04B: MSM79V035) is processed by a register contained in the SP/LF motor driver to measure the overdrive time and to change the phase.

Page: 34

Service Guide ML520/521

Chapter 2 Principles of Operation

Space Motor Control

The SP/LF motor driver (Location 5A: MHM2025) drives the three-phase brushless motor. Motor movement is based on the phase signal (SPU, SPV and SPW) and the speed instruction data from the LSI. The MPU can identify the current speed of the space motor by measuring the pulse width of the output (Phase A, Phase B) of the encoder disk sensor.

After comparing the target speed for each print mode with the actual speed, the motor is accelerated or decelerated to maintain the desired speed for each print mode.

Page: 35

Service Guide ML520/521

Chapter 2 Principles of Operation

Encoder Disk

As the space motor operates, the encoder disk spins. When the encoder disk interrupts the photo sensors, the signals Phase A and Phase B are generated. The LSI (Location 04B: MSM79V035) divides these edge pulse signals (the frequency division is based on the selected print pitch) to generate the signal IPT. The IPT signal provides dot-on timing and carriage position detection timing.

Page: 36

Service Guide ML520/521

Chapter 2 Principles of Operation

2.1.06 Operation Panel

The Serial I/O Port (Ports 20 - 23) of the MPU reads the operation panel switch data from the operation panel control LSI (Location IC1: BUS148S).

A two byte (15 bits +1 parity bit (even parity)) command (OPTXD) is transmitted from the MPU to the operation panel LSI in synchronization with the OPCLK signal. Once the LSI decodes the command, the command must pass a command code check and have no parity errors. Then, the specified I/O control will return the two byte command response to the MPU.

Page: 37

Service Guide ML520/521

Chapter 2 Principles of Operation

2.1.07 Alarm Circuit

Driver Circuit Alarm Processing

The printhead driver output and the head gap magnet output drive signals are monitored at R29 and C8. The POWER OFF-P signal is output by the comparator (Location 02C: IC2901) when driven for more than the specified time. This signal becomes the ALM signal. The ALM signal is sent to the power supply board and causes the DC voltages to be turned off.

Page: 38

Service Guide ML520/521

Chapter 2 Principles of Operation

Low Motor Drive Voltage Alarm

+40V is converted into the POWLEV signal (0 vdc to +5 vdc) by the voltage divider network of R542 and R544, then input to the A/D port of the MPU. The value of this voltage is used to control the drive time and the print speed (pass number) of the head.

Page: 39

Service Guide ML520/521

Chapter 2 Principles of Operation

Head Drive Time

The head drive time is modified to compensate for the amount of the voltage drop of the POWLEV signal. By monitoring the voltage drop every 500 microseconds, the MPU is able to control and maintain the impact necessary for each printhead pin.

Print Speed

Page: 40

Service Guide ML520/521

Chapter 2 Principles of Operation

Actual Voltage (+40 vdc)

Passes Required Relative Print Speed

+34 vdc or greater 1 100% +32 vdc to +34 vdc 1 Approximately 85% +30 vdc to +32 vdc 1 Approximately 50%

+30 vdc or less 2 Less than 50%

Page: 41

Service Guide ML520/521

Chapter 2 Principles of Operation

Head Overheat Alarm Processing

If the printhead temperature exceeds 110 degrees Celsius, the printer will switch to uni-directional print. If the temperature exceeds 118 degrees Celsius, printing will stop. Once the printhead cools, printing will resume.

Two thermistors are used to monitor the printhead temperature. One is contained in the printhead. The other is in the printhead driver.

A thermistor in the printhead prevents over-heating of the coil during periods of continuous bi-directional printing. If the temperature of the coil exceeds the pre-determined limits, the control circuit detects the thermistor signal (TSD).

Another thermistor monitors the temperature of the printhead driver. If the temperature of the driver exceeds the pre-determined limits, the control circuit detects the thermistor signal (TSD).

The voltage of the TSD signal is monitored at the MPU A/D port to control the pass number and print method (uni-directional / bi-directional) at each of seven levels.

Service Guide ML520/521

Chapter 2 Principles of Operation

2.1.08 Power Supply Circuit

The switching type power supply circuit supplies the +5 vdc, +/-8 vdc, 10 VAC and +40 vdc.

Page: 42

Voltage/Signal

+5 vdc IC logic levels, LED drive voltages +8 vdc Serial interface line voltage, comparator IC +10 VAC Serial interface line voltage and the printhead analog circuit +40 vdc Printhead, space motor and line feed motor drive voltage

Purpose

Page: 43

Service Guide ML520/521

Chapter 2 Principles of Operation

2.2 MECHANICAL OPERATION

2.2.01 Printhead Mechanism

The printhead is a spring-charged, 9-pin printhead. It is attached to the carriage, which moves parallel to the platen. Electrically, the printhead is controlled by the main control board via the carriage cable and the space motor.

The printhead is composed of the following parts. Wire Guide Spring Assembly

Wire, Armature, Spring, Yoke, Spacer

Magnet Assembly

Magnet, Core, Coil, Yoke

Printed Circuit Board

Logic Control, Print Driver, Analog Sensor Control and Thermistor

Cooling Fin

Service Guide ML520/521

Chapter 2 Principles of Operation

Printhead Gap Information

Three items factor into printhead gap information.

1. Printhead Gap Adjustment This is a SERVICE ADJUSTMENT made by a technician. It is covered in Section 3.3 of this Service Handbook. The Adjustment measures 0.014, +/- 0.001 inches (0.35, +/- 0.03 mm).

2. Printhead Gap Adjust This is a MENU ITEM in the SET-UP Group. It fine tunes the automatic setting of the printhead gap.

Page: 44

The settings are 0, 1, and -1. 0 is the factory default. Use 1 to Use - 1 to

3. Gap Control This is a MENU ITEM in The Groups are REAR FEED, BOTTOM FEED, and TOP FEED. Gap Control determines how the printhead gap is set. The settings are listed below. Auto Gap, Semi Auto Gap, 1, 2, 3, 4, 5, 6, 7, 8, 9 An explanation of each setting follows.

Auto Gap

This is the factory default.

darken

lighten

print (if output is

each

[Paper Feed] Group.

consistently light

consistently dark

Automatically determines paper thickness of the first page. During single-sheet feed, each pages thickness is checked

while

a job is printing.

Semi Auto Gap

Similar to Auto Gap. Automatically determines paper thickness of the first page. During single-sheet feed, each pages thickness IS NOT checked while a job is printing.

1, 2, 3, 4, 5, 6, 7, 8, 9

Used when the same paper is used ALL of the time. Bypasses the automatic head gap adjustment. 1 is the narrowest gap setting. 9 is the widest gap setting.

Service Guide ML520/521

Chapter 2 Principles of Operation

Interconnect Diagram: Control Board to Printhead

NOTE:

The printhead coil resistance values ARE NOT LISTED. The individual printwire control lines CANNOT be accessed on this printhead.

Page: 45

Service Guide ML520/521

Chapter 2 Principles of Operation

Line Feed Motor Resistance

The resistance of each coil should be approximately 13 ohms.

Page: 46

Service Guide ML520/521

Chapter 2 Principles of Operation

Space Motor Resistance

The resistance of each coil should be approximately 5 ohms.

Page: 47

Page: 48

Service Guide ML520/521

Chapter 2 Principles of Operation

Printhead Operation

When the printhead is idle, the armature is attracted to the permanent magnet. The print wires, which are attached to each armature, are then concealed inside the wire guide.

When a signal to print a character is received, current flows through a coil. The magnetic field generated by the coil opposes the magnetic field between the armature and the permanent magnet. The armature is then driven in the direction of the platen by the force of the armature spring. The print wire (which is attached to the armature) protrudes from the tip of the wire guide and strikes the paper through the ribbon. This prints a dot on the paper.

As the armature gets closer to the electrode of the analog sensor, the capacitance between them increases and a small amount of current flows. This current is amplified and sent to the logic control LSI to indicate armature activity. In order to attain optimum drive time, this information is transferred to the MPU. The MPU continually modifies the head gap to maintain the optimum drive time condition.

The analog sensor element monitors all of the pins. The difference in pin stroke due to the curvature of the platen is compensated for at the logic control section of the printhead and is not transferred to the MPU.

After the character has been printed, the permanent magnet attracts the armature and the print wires are retracted into the wire guide.

Page: 49

Service Guide ML520/521

Chapter 2 Principles of Operation

Printhead Temperature

Two thermistors are used to monitor the printhead temperature. One is contained in the printhead. The other is in the printhead driver.

Another thermistor monitors the temperature of the printhead driver. If the temperature of the driver exceeds the pre-determined limits, the control circuit detects the thermistor signal (TSD). The voltage of the TSD signal is monitored at the MPU A/D port to control the pass number and print method (uni-directional / bi-directional) at each of seven levels.

Page: 50

Service Guide ML520/521

Chapter 2 Principles of Operation

2.2.02 Spacing Mechanism

The spacing mechanism consists of a carriage shaft (mounted parallel to the platen), and a carriage frame which moves along the shaft. The carriage frame is driven by a DC servo motor mounted on the carriage frame.

Items included in the spacing mechanism are listed below.

Space Motor Assembly

DC Servo Motor

Motor Gear

Sensor Encoder Disk

Carriage Frame Carriage Shaft Space Rack

Page: 51

Service Guide ML520/521

Chapter 2 Principles of Operation

Spacing Operation

The carriage frame, which contains the printhead and space motor, moves along the carriage shaft parallel to the platen. When the space motor rotates, the driving force is transmitted to the motor gear. As the motor gear rotates, the carriage moves along the platen. For every revolution of the DC servo motor, the carriage frame moves 0.8 inch (20.32 mm).

As the DC servo motor rotates, a slotted disk (called the encoder disk), rotates with the servo motor and passes through the photosensor. The position of the carriage frame can be determined by counting the pulses generated by the photosensors.

In the same way, the rotation of the space motor can be recognized and controlled by measuring the phase relationship and the pulsewidth of the signals generated by the photosensors.

Page: 52

Service Guide ML520/521

Chapter 2 Principles of Operation

2.2.03 Head Gap Mechanism

The head gap is automatically set for the thickness of the medium loaded in the printer. In the case of envelopes, where the medium thickness varies as the printhead moves along the platen, the strike force of the pins changes to compensate for the differences in thickness.

Head Gap Setting Operation

Once printing starts, the space motor rotates the ribbon gear, causing idle gear C to turn the change gear. When the MPU requests a change in the head gap setting, the GAP-P signal causes the armature (which

is holding the change gear) to be attracted to the pranger magnet. The gap reset spring can now push the change gear so it contacts the gap change gear.

The rotation of the gap change gear causes idle gear D to turn the adjust gear. The adjust gear turns the adjusting screw, resulting in a new head gap setting.

NOTE:

As the adjusting screw turns counter-clockwise, the gap narrows. As the adjusting screw turns clockwise, the gap widens.

There is a cam at each setting of the gap change gear. When the change gear is at the top of the cam, the change gear disengages from the gap change gear. At this time, the armature resets, changing the head gap by one setting.

The head gap is modified in .06 mm units for each range setting.

Page: 53

Service Guide ML520/521

Chapter 2 Principles of Operation

Ribbon Drive Operation

The ribbon drive mechanism feeds the ribbon in synchronization with the spacing operation. The force required to drive the ribbon is obtained from the space motor.

The ribbon drive mechanism is composed of the items listed below. Ribbon Drive Gear Assembly Ribbon Gear

This gear is located on the space motor assembly

Ribbon Cartridge

A continuous loop ribbon with uni-directional feed is used. Ink is supplied from an ink tank,

which is built into the ribbon cartridge. When the space motor turns, the ribbon gear on the spacing motor shaft rotates. The rotation is

transmitted via a combination of gears, from the ribbon drive gear assembly to the drive gear in the ribbon cartridge.

Although the space motor moves in both the forward and reverse directions during bi-directional printing, the gears in the ribbon drive assembly maintain uni-directional ribbon feed by switching the rotation direction of the gears.

Service Guide ML520/521

Chapter 2 Principles of Operation

2.2.05 Line Feed Mechanism

The line feed operation is accomplished by activating the line feed motor which turns the platen. The rotation of the platen is used to feed paper from the selected paper path.

The components of the paper feed mechanism are listed below.

Line Feed Motor (pulse motor), with gears Line Feed Idler Gear Platen Rear Tractor Feed Unit Pressure Roller

Page: 54

Change Lever (Paper Path Selection Lever)

The change lever is used to select one of three different paper paths; top, rear or bottom.

Paper Clamp Mechanism

Moving the change lever between the bottom, top and rear positions, changes the positions of the front release gear arm and the release cam.

The movement of the front release gear arm changes the position of the front release gear shaft. This causes the front pressure roller to open or close.

The movement of the release cam causes the rear pressure roller to open or close.

Page: 55

Service Guide ML520/521

Chapter 2 Principles of Operation

Cut Sheet/Continuous Sheet Switching Mechanism

Top Feed (for cut sheet paper)

When cut sheet paper is used during normal operation or by the Cut Sheet Feeder (CSF) option, place the change lever in the Top Feed position.

As the platen turns, the platen gear causes the idle gear to rotate. At this time, the rear and front pressure rollers are pressed securely to the platen to feed the cut sheet. The cut sheet detection lever enables the cut sheet detection switch (which is located on the main control

board). This places the printer in the cut sheet mode. When cut sheet paper is placed between the platen and the paper chute, the printer automatically feeds

the sheet to the print start position.

Rear/Bottom Feed (for continuous feed paper)

When the continuous feed paper is used, either with the rear tractor, optional bottom tractor or optional pull tractor, place the change lever in the Rear/Bottom Feed position.

When the change lever is placed in this position, the reset spring pushes the change gear. In this position, the idle gear is engaged with the bottom tractor unit drive gear and the tractor gear. As the platen turns, power is transferred from the platen gear, to the idle gear, to the change gear, and then to the push tractor shaft.

CAUTION:

The cut sheet / continuous sensor lever must be positioned below the BASW sensor. The lever should contact the sensor only when the change lever is in the top feed (middle) setting. If the lever is not correctly positioned, the ALARM lamp will light and the unit will not automatically load paper or receive data.

Page: 56

Service Guide ML520/521

Chapter 2 Principles of Operation

Cut Sheet Paper Feed Operation

As the line feed motor rotates, power is transferred through the decelerating gears (line feed idler gear, platen gear) to the platen.

When using cut sheet paper, the change lever must be in the TOP position so the platen and pressure rollers can feed the paper. This also disengages the push tractor.

Page: 57

Service Guide ML520/521

Chapter 2 Principles of Operation

Continuous Paper Feed (Rear Tractor Mechanism)

As the platen rotates, power is transferred to the tractor gear from the platen gear, the idler gear, and the change gear. The tractor gear drives the pin tractor belts, which feed the continuous paper.

Page: 58

Service Guide ML520/521

Chapter 2 Principles of Operation

Continuous Paper Feed (Pull Tractor Mechanism)

only

Bottom feed of continuous sheets is possible As the platen rotates, power is transferred to the drive gear from the line feed idler gear, the platen gear, idler gear B and idler gear A. The drive gear turns the pull tractor assembly, which feeds the continuous paper.

when an optional pull tractor unit is installed.

Page: 59

Service Guide ML520/521

Chapter 2 Principles of Operation

Continuous Paper Feed (Bottom Tractor Feed Mechanism)

As the platen rotates, power is transferred to the drive gear from the platen gear, the idle gear and the tractor change gear. The drive gear turns the pin tractor belts on the bottom tractor feed unit, which feeds the continuous paper.

Service Guide ML520/521

Chapter 2 Principles of Operation

Continuous Paper Feed (Push/Pull Tractor Mechanism)

This mechanism consists of an optional pull tractor and a standard push tractor mechanism. Continuous paper is fed by these two tractors at the same time.

Page: 60

Page: 61

Service Guide ML520/521

Chapter 2 Principles of Operation

2.2.06 Paper Detection Mechanism

Top Feed Paper Detection

When cut sheet paper is inserted into the printer, Point A of the Rear/Top Paper Feed Lever is pushed backward, causing the Sensor Lever to rotate.

As the Sensor Lever rotates, it contacts the Rear Sensor Lever. This makes the Rear Sensor Lever rotate. The Rear Sensor Lever rotates, unblocking the Rear / Top Paper End Sensor (SNS1).

Rear Feed Detection

When paper is fed from the Rear Push Tractor, Point B is pushed backward. This makes the Sensor Lever rotate.

As the Sensor Lever rotates, it contacts the Rear Sensor Lever. This makes the Rear Sensor Lever rotate. The Rear Sensor Lever rotates, unblocking the Rear / Top Paper End Sensor (SNS1).

Bottom Feed Detection

When the paper is fed from the bottom of the printer, Point C is pushed, rotating the Bottom Paper End Lever.

As the Bottom Paper End Lever rotates, it contacts the Bottom Sensor Lever. This makes the Bottom Sensor Lever rotate.

The Bottom Sensor Lever rotates, unblocking the Bottom Paper End Sensor (SNS2).

NOTE:

The method for detecting a paper-end condition is the reverse of the above. PAPER-END is detected when the Bottom Paper End Sensor (SNS2) is blocked.

Page: 62

Service Guide ML520/521

Chapter 2 Principles of Operation

2.2.07 Support Protector Mechanism

During printer initialization, the support protector is latched in the stored position (approximately 5 mm from the left bracket of the main frame).

Just before paper is loaded, the printhead moves towards the left bracket and unlatches the support protector.

As the printhead moves to the right, the support protector reset spring pushes the support protector toward the center of the platen. With the support protector in this position, the ribbon protector and the support protector prevent the leading edge of the paper from curling or folding. Once the paper is ejected, the printhead slowly moves towards the left bracket. The support protector is latched in the stored position when it is pushed to approximately 5 mm from the left bracket.

Page: 63

Service Guide ML520/521

Chapter 2 Principles of Operation

2.2.08 Automatic Paper Load

The Microline 520/521 printers will automatically detect cut sheet paper and feed the paper to the Top of Form (TOF) position.

Cut Sheet Paper

Set the change lever to the TOP FEED position.

NOTE:

When the change lever is in the TOP FEED position, the cut sheet detection lever contacts the cut sheet detection switch (BASW), which is located on the main control board.

Insert the sheet of paper between the platen and the paper chute. Once paper is detected at the paper end sensor and the amount of time selected on the

of the menu has lapsed, the line feed motor will feed the paper until the leading edge of the paper reaches the top of form position.

Wait Time

setting

Page: 64

Service Guide ML520/521

Chapter 2 Principles of Operation

Continuous Feed Paper

Set the change lever to either the REAR FEED or BOTTOM FEED position.

NOTE:

When the change lever is in the REAR FEED or BOTTOM FEED position, the cut sheet detection lever does NOT contact the cut sheet detection switch (BASW), which is located on the main control board.

Place continuous feed paper in the appropriate tractor. Press the FF/LOAD switch. The line feed motor will feed the paper until the leading edge of the paper reaches the top of form position.

Page: 65

Service Guide ML520/521

Chapter 2 Principles of Operation

2.2.09 Paper Park

If continuous feed paper is installed and printing on cut sheet paper is desired, it is not necessary to unload the continuous feed paper. The Paper Park feature provides a means of retracting the continuous feed paper from the paper path, while (at the same time) cut sheet paper is fed.

Paper Park Operation

Place the change lever in the REAR FEED or BOTTOM FEED position. Press the PARK switch on the operation panel. A reverse line feed operation retracts the paper until paper-end occurs or 19 inches of paper have been

retracted.

NOTE:

Retracting 19 inches of paper without detecting a paper-end condition causes the line feed operation to stop. The line feed operation stops because the printer assumes a jam has occurred.

The operator can press the SEL switch to reset the ALARM LED and press the PARK switch to continue the park operation.

This operation may be useful when length of the paper to be parked is greater than 19 inches.

Page: 66

Service Guide ML520/521

Chapter 3 Maintenance & Disassembly

3.1.01 General Information

This section lists the parts replacement, adjustment, cleaning, lubrication, and shipping procedures. Disassembly should not be performed unless absolutely necessary.

malfunctioning printer until you have followed the failure analysis procedures in Section Four of this Service Handbook.

Follow the procedures listed in either consumable or parts are replaced. Failure to perform these procedures could result in unnecessary service calls.

Proper performance of maintenance and cleaning will help to achieve the best possible print quality from the printer.

Adjustments and Service Settings

NEVER

. Adjustments may be required when

perform disassembly on a

Service Guide ML520/521

Chapter 3 Maintenance & Disassembly

3.1.02 Maintenance Tools

The following tools are required to service the printer. #2 Phillips Screwdriver (with magnetic tip) Straight-slot Screwdriver Needle Nose Pliers (4 Inch) Wire Cutters Digital Multimeter Feeler Gauge (capable of measuring .014 inches) Shop Vacuum Clean, soft, and lint-free Cloth All-Purpose Cleaner Contact Kleen (Okidata P/N 51802301)

Page: 67

Platen Cleaner Machine Grease Machine Oil

Page: 68

Service Guide ML520/521

Chapter 3 Maintenance & Disassembly

3.1.03 Maintenance Precautions

1. Do not disassemble the unit if it is operating normally.

2. Before starting disassembly and assembly, always turn the AC power switch OFF and pull out the AC plug.

3. Detach the interface cable, if installed.

4. Do not remove parts unnecessarily. Try to keep disassembly to a minimum.

5. Use the recommended maintenance tools.

6. When disassembling, follow the listed sequence. Failure to follow the correct sequence may result in damaged parts.

7. Since screws, collars and other small parts are easily lost, they should be temporarily attached to the original positions.

8. When handling circuit boards use extreme care. Integrated circuits (microprocessors, ROM, and RAM) can be destroyed by static electricity.

9. Do not place printed circuit boards directly on conductive surfaces.

10. Follow the recommended procedures when replacing assemblies and units.

11. Perform the printhead gap adjustment procedure

Handbook) when the any of the following occur.

Print Quality is darker on one side of the document. Parts are replaced

Printhead (3.2.02) Space Motor Assembly (3.2.11) Space Rack (3.2.13) Guide Rail (3.2.15) Platen Assembly (3.2.19) Carriage Shaft (3.2.25)

(Refer to Section 3.3 of this Service

Page: 69

Service Guide ML520/521

Chapter 3 Maintenance & Disassembly

3.2 DISASSEMBLY/ASSEMBLY PROCEDURES

General Information

This section contains the printer disassembly procedures. Only the removal procedures are explained here. Reverse the procedure for the installation.

At the bottom of each procedure is a listing of the parts covered in that procedure. The Okidata part number, item description, comment (RSPL, Option, Consumable) and cross-reference to Appendix B is provided for each part. Items included in the Recommended Spare Parts List are indicated by the acronym RSPL. N/A will appear where a part number is not available.

520 indicates that the item is specific to the Microline 520. 521 indicates that the item is specific to the Microline 521. Both indicates that the item is common to both printers.

This Service Handbook lists the disassembly procedures for major components of the unit. Okidata DOES NOT recommend disassembling a unit which is operating normally. If you decide to perform disassembly

only

during this training, Okidata recommends that you perform items. All other procedures are provided to assist you in identifying parts. It is not likely that you will perform these procedures while servicing the unit. Be sure to read all notes, cautions, and warnings, as they contain important information regarding disassembly / assembly.

the disassembly procedures for RSPL

Service Guide ML520/521

Chapter 3 Maintenance & Disassembly

3.2.01 Preliminary Items

1. Press the AC switch (1) and power off the printer.

2. Remove the paper, if installed (2).

3. Detach the AC power cord (3).

4. Detach the interface cable, if installed (4).

P/N 56609701 Cord: AC RSPL Both B.2.03

P/N 56624101 Cord: AC 220V (ML Series) Right Angle Option RSPL Both B.2.03

P/N 56624401 Cord: AC 240V Option RSPL Both B.2.08

P/N 70000803 Kit: Parallel Interface Option Both B.2.08 Plug n Play Accessory

Page: 70

P/N 70012801 Kit: RS232-C Serial Interface Option Both B.2.08

Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)

3.2.02 Printhead Assembly

Perform this procedure: 3.2.01.

2. Open the access cover (1).

Page: 71

Service Guide ML520/521

Chapter 3 Maintenance & Disassembly

3. Lift and remove the ribbon. (

4. Pull the head clamp (2) towards the right and then rotate it up to release the printhead (3).

5. Pull the printhead straight up to remove it.

NOTE:

Installation

this Service Handbook.

P/N 52107001 Ribbon: Black Consumable Both B.2.10

P/N 50707401 Clamp: Head RSPL Both B.2.07

P/N 50099501 Assembly: Printhead RSPL Both B.2.03

After installing the printhead, check the printhead gap adjustment.

Not shown

)

Refer to Section 3.3 of

Page: 72

Service Guide ML520/521

Chapter 3 Maintenance & Disassembly

3.2.03 Ribbon Protector

CAUTION

You MUST use a straight slot screwdriver to release the ribbon protector. If you attempt to lift the protector without releasing the tabs, the protector will break.

Perform these procedures: 3.2.01

2. Open the pull-up roller cover (1).

3. Use a straight-slot screwdriver to release the extensions (2) from the carriage frame set (3).

4. Lift the ribbon protector (4) straight up and remove it.

P/N 53562801 Protector: Ribbon RSPL Both B.2.07

, and 3.2.02

3.2.04 Gear Case Assembly

Page: 73

Service Guide ML520/521

Chapter 3 Maintenance & Disassembly

Perform these procedures: 3.2.01

2. Use a straight-slot screwdriver to release the four claws (1) of the gear case assembly (2).

3. Lift and remove the gear case assembly.

NOTE:

Lubrication ---

P/N 51228501 Gear: Case (Assembly) RSPL Both B.2.07

When lubricating, refer to Section 3.5 of this Service Handbook.

, and 3.2.02 .

Service Guide ML520/521

Chapter 3 Maintenance & Disassembly

3.2.05 Pull-up Roller Assembly

Perform this procedure: 3.2.01.

2. Open the access cover (1).

3. Open the cover of the pull-up roller assembly (2).

4. Press at A while rotating the assembly towards the back of the printer.

5. Remove the assembly.

NOTE: Lubrication

When lubricating, refer to Section 3.5 of this Service Handbook.

Page: 74

P/N 53341501 Roller: Pull Up Assembly (Narrow) RSPL 520 B.2.05

P/N 53341601 Roller: Pull Up Assembly (Wide) RSPL 521 B.2.05

Oki ML520 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual