ML520 // ML521 Dot Matrix Printers
About This Manual
 Service Guide ML520/521
 Maintenance & Disassembly
 Failure & Repair Analysis
 Illustrated Parts Listing
 Table of Contents
 Service Guide ML520/521
Page
 Product Specifications General Information
 Printer Weight Microline
Microline
 Product Specifications
Power Requirements
 Ambient Temperature and Relative Humidity RH
Altitude
 Product Specifications Agency Approvals 1.5.01 Listings
 IPS
CPI CPS
Horiz. DPI Vert. DPI
HSD
 UPC a UPC E EAN
 Emulations
Front Panel Switches
Graphics Resolution
Fonts Near Letter Quality
 Selects Group Function
Menu Mode Switch Action
Line Feed Increments Fixed
Form Feed / Load Selects Item
 Paper Tear Capabilities
Paper Loading
Paper Out Detection
Print Method Printhead Type General Information
 Auto Gap
Printhead Gap Adjustment
Gap Control
Semi Auto Gap
 Print Modes
80 12 cpi 320 12 cpi 427 12 cpi
 Continuous Form
Paper Specifications
Types Card Stock
Cut Sheet
 Envelopes
Labels
Transparency
 Number of Copies
Weight
Length
Thickness
 Width
Paper
Printing Area
 Eprom
Memory Specifications
Eeprom
03 RAM
 Product Specifications Consumables 1.9.01 Ribbon
 Dual Bin
Page
 Product Specifications Pull Tractor Kit
 Product Specifications Bottom Push Tractor Kit
 Product Specifications Serial Interface
 Product Specifications Roll Paper Stand
 Product Specifications OKISmart Typer Utility
OKISmart Panel Utility
 Reliability
 Principles of Operation
Electrical Operation
 Principles of Operation Main Control Board
 Principles of Operation Block Diagram
 Principles of Operation Program ROM
 RAM
 LSI
 Service Guide ML520/521
 Reset operation initiated by I-PRIME does not reset the MPU
Principles of Operation Initialization
 Principles of Operation Parallel Interface Control
 Principles of Operation Print Control
 Principles of Operation LSI/Printhead Interface
 Principles of Operation Gap Adjust Control
 Principles of Operation Print Compensation Control
Also refer to .1.07 Head Drive Time
 Service Guide ML520/521
 Principles of Operation Line Feed Motor Control
 Principles of Operation Space Motor Control
 Principles of Operation Encoder Disk
 Principles of Operation Operation Panel
Page
 Service Guide ML520/521
 Principles of Operation Low Motor Drive Voltage Alarm
 Principles of Operation Head Drive Time
 Less than 50%
+34 vdc or greater
 Principles of Operation Head Overheat Alarm Processing
 Principles of Operation Power Supply Circuit
Voltage/Signal Purpose
 Service Guide ML520/521
 Principles of Operation Printhead Gap Information
Page
 Service Guide ML520/521
 Principles of Operation Line Feed Motor Resistance
 Principles of Operation Space Motor Resistance
 Principles of Operation Printhead Operation
Page
 Principles of Operation Printhead Temperature
 Principles of Operation Spacing Mechanism
 Principles of Operation Spacing Operation
 Head Gap Setting Operation
Principles of Operation Head Gap Mechanism
Page
 Principles of Operation Ribbon Drive Operation
Page
 Principles of Operation Line Feed Mechanism
Change Lever Paper Path Selection Lever
Paper Clamp Mechanism
Page
 Rear/Bottom Feed for continuous feed paper
Page
 Principles of Operation Cut Sheet Paper Feed Operation
 Service Guide ML520/521
 Service Guide ML520/521
 Service Guide ML520/521
 Service Guide ML520/521
 Rear Feed Detection
Bottom Feed Detection
Page
 Principles of Operation Support Protector Mechanism
 Principles of Operation Automatic Paper Load
Cut Sheet Paper
 Principles of Operation Continuous Feed Paper
 Principles of Operation Paper Park
Paper Park Operation
 Maintenance & Disassembly General Information
 Maintenance & Disassembly Maintenance Tools
 Maintenance & Disassembly Maintenance Precautions
Handbook when the any of the following occur
 Service Guide ML520/521
 Maintenance & Disassembly Preliminary Items
Page
 Maintenance & Disassembly Printhead Assembly
Perform this procedure
Page
 Maintenance & Disassembly Ribbon Protector
Perform these procedures 3.2.01 ,
53562801 Protector Ribbon Rspl Both B.2.07
 Maintenance & Disassembly Gear Case Assembly
 Maintenance & Disassembly Pull-up Roller Assembly
 When cleaning, refer to .4 of this Service Handbook
Page
 Maintenance & Disassembly Control Board Fjim
Installation
Page
 Maintenance & Disassembly Power Supply Assembly
Page
 Maintenance & Disassembly Operator Panel PCB Leop
Perform these procedures 3.2.01 , 3.2.06 ,
 Maintenance & Disassembly PC Connector
Perform these procedures 3.2.01 , 3.2.02 ,
 56729601 Connector PC HD40 Rspl Both B.2.07
 Perform these procedures 3.2.01 , 3.2.02 , 3.2.04 ,
Page
 Maintenance & Disassembly Carriage Cable
Perform these procedures 3.2.01 , 3.2.06 , 3.2.07 ,
 Maintenance & Disassembly Space Rack
When cleaning, refer to .4 of this Service Handbook
Page
 Maintenance & Disassembly Roller/Holder Backup Assembly
 Maintenance & Disassembly Guide Rail and Adjust Cam
Page
 Maintenance & Disassembly Left Ground Plate
51010301 Plate Left Ground Rspl Both B.2.04
 Maintenance & Disassembly Right Ground Plate
51010201 Plate Right Ground Rspl Both B.2.05
 Perform these procedures 3.2.01 , 3.2.06 , 3.2.07 , 3.2.16 ,
 Maintenance & Disassembly Platen Assembly
When lubricating, refer to .5 of this Service Handbook
Page
 Maintenance & Disassembly Paper Chute Assembly
Page
 Maintenance & Disassembly Line Feed Motor Assembly
 56627201 Cord Connection Line Feed Rspl Both B.2.04
 Maintenance & Disassembly Reset Spring
50923201 Spring Reset Rspl Both B.2.05
 Maintenance & Disassembly Idle Gear and Change Lever
Page
 Maintenance & Disassembly Pressure Spring
Page
 Maintenance & Disassembly Carriage Shaft
Page
 Maintenance & Disassembly Leaf Spring
Page
 Maintenance & Disassembly Bottom Paper Sensor Levers
Page
 Maintenance & Disassembly Front Pressure Roller Assembly
Page
 Maintenance & Disassembly Tractor Assembly
Page
Page
 Maintenance & Disassembly Main Frame
 Service Guide ML520/521
 Procedure Setup Phase
 Printhead Gap Modification Phase
Parallel Adjustment Phase
Verification Phase
Page
 Maintenance & Disassembly Key Combinations Description
SEL + FF/LOAD
 Menu Mode
Printing the Menu
 Reset Menu to Factory Defaults
Procedure
Limited Operation General Information
Page
 Maintenance & Disassembly Menu Settings
Group Setting
 Valid
 Yes No
Page
 Maintenance & Disassembly Top of Form General Information
Setting Top of Form
Reset the Top of Form to Factory Default
 Maintenance & Disassembly Paper Park General Information
Procedure Continuous Feed to Single Sheet
Procedure Single Sheet to Continuous Feed
 Maintenance & Disassembly Tear Feature
 Maintenance & Disassembly Forms Tear Off
Vertical Line Spacing Problems
 Using
Checking Top of Form with Form Tear Off Activated
 Factory default Top of Form Setting is 1 inch
 Cleaning Schedule
Maintenance & Disassembly
Cleaning
Cleaning Tools
 Lubrication Types
Lubrication
Lubrication Schedule
Lubrication Amounts
 Areas Not Lubricated
 Return for Service
Shipping Instructions
All Other Returns
 Failure & Repair Analysis Introduction
 Service Guide ML520/521
 Failure & Repair Analysis Firmware Revision Identification
Header
 Service Guide ML520/521
 Failure & Repair Analysis Problem Lists
 Fax Number
Failure & Repair Analysis Reporting Methods Okilink
Course Critique
Mailing Address
 Technical Service Bulletins
Okilink
Faxable Facts
 Service Guide ML520/521
 Operational Errors
Failure & Repair Analysis Problem Categories
Alarm Lamp Blinks Fatal Errors
Alarm Lamp Lights Paper End/Jam Conditions
 Failure & Repair Analysis Start Here Flowchart
Start
 Failure & Repair Analysis Tips for Preventing Image Problems
This Service Handbook
 Failure & Repair Analysis Common Problems
 Always power OFF the printer before you turn the platen knob
Page
 Uneven Print Density
 Smeared Print
Inconsistent Line Feed
 Drifting Margin
 Failure & Repair Analysis Left Margin Drifting Problem
 Fault Alarms
Failure & Repair Analysis
 Alar Utility PRO NLQ HSD Menu
 Blinkin Kin
 Refer to RAP
Page
 Service Guide ML520/521
 Failure & Repair Analysis RAP Index RAP Number Description
 Start
Page
 Failure & Repair Analysis RAP 02 No Spacing Operation
Page
 Failure & Repair Analysis RAP 03 Printhead Homing Error
Page
 Service Guide ML520/521
 Failure & Repair Analysis RAP 05 Printhead Pins Not Firing
 Failure & Repair Analysis RAP 06 Poor Print Quality
 Failure & Repair Analysis RAP 07 Ribbon Feed Problem
 Failure & Repair Analysis RAP 08 Line Feed Problem
Page
 Failure & Repair Analysis RAP 09 Operation Panel Malfunction
 Failure & Repair Analysis RAP 10 Parallel Interface Problem
Page
 Failure & Repair Analysis RAP 11 Serial Interface Problem
 Handbook
 Printer Tests
 Procedure
Page
 Failure & Repair Analysis Font Test General Information
Page
 Loopback Connector Configuration
Failure & Repair Analysis Serial Interface Loopback Test
Page
 Failure & Repair Analysis Serial Cable Information
 Service Guide ML520/521
 Service Guide ML520/521
 Example
Hex Data Dump
 Service Guide ML520/521
 Layout Diagram
 Service Guide ML520/521
 Failure & Repair Analysis Line Feed Motor Resistance
 Failure & Repair Analysis Space Motor Resistance
 Service Guide ML520/521
 Chapter a Reference Charts
Description Board Designation Section Main Controller Board
Operator Panel Board
 Chapter a Reference Charts Board Layout
 Fuses
Switches
Firmware
Jumpers
Page
 Shift
Page
 Chapter a Reference Charts Power Supply Assembly Function
Page
 Chapter a Reference Charts Space Motor Board Function
Page
 Masked to the MPU Socket is empty
Page
 Service Guide ML520/521
 Chapter B Illustrated Parts Listing Format
 Chapter B Illustrated Parts Listing Current Part Numbers
Remember
 Rspl
 520
521
Both
 Placing a Parts Order
 Charts
 Chapter B Illustrated Parts Listing Overview
 Comments
Refer to
 Comments Refer to
 53067201 2PA4094-7382G1 Cover Access Wide Rspl
 ROM
 PCB Leop
 Service Guide ML520/521
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 Service Guide ML520/521
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 Service Guide ML520/521
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Page
 Service Guide ML520/521
 N/A
 Service Guide ML520/521
 PCB Lxhi
 Service Guide ML520/521
 PCB Ncsf
 Chapter B Illustrated Parts Listing Consumables
52107001 N/A Ribbon Black Consumable Both
 Comments Refer
To B.1.02
 Service Guide ML520/521
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 Okidata P/N Oki-J Description
 Comments Refer
 Comments Refer