Oki ML520, ML521 manual Always power OFF the printer before you turn the platen knob

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Handbook, the more compatible it will be with your printer. If your software does not have any of the indicated drivers available, check with the software manufacturer to see if they have added any additional drivers since you purchased your software.

If you have embedded any printer commands in your software, check to be sure that you have entered them correctly.

7. Printing on the right side of the page is lighter or darker than the rest of the print on the page.

Although the printer automatically sets the head gap, it sometimes may need a minor adjustment. To make this adjustment, enter the Menu Mode. Press SEL and SHIFT buttons simultaneously. To change the setting for the Printhead Gap Adjust under the Setup Group, use the following procedure.

Press GROUP until Setup Group prints.

Press ITEM until Printhead Gap prints.

Press SEL to change the setting. The default setting is 0. If the printing is sometimes lighter, change the setting to - 1. If it is sometimes darker, change it to + 1.

Press SEL and SHIFT buttons simultaneously to exit Menu Mode.

8. There are vertical spacing problems when using continuous forms and Forms Tear Off.

The printer does not have a bail arm, so pages do not feed as high as printers with bail arms. The first page does not line up correctly. Enter Menu Mode and disable Form Tear Off. Exit Menu Mode. Deselect the printer and set the paper position, using the Micro Feed buttons (hold SHIFT while pressing MICRO FEED UP or DOWN). Enter Menu Mode and enable Form Tear Off. Exit Menu Mode.

9. The ALARM light is not on, but paper needs to be loaded.

If the ALARM light is off, the printer "thinks" that paper is loaded. To correct this problem, press and release the SEL button. Then, hold the SHIFT button and press the RESET (Character Pitch) button. The ALARM light will come on and you will be able to load paper.

10. The ALARM light is on and the Character Pitch 15 light is blinking.

This indicates a paper loading error. To stop the blinking light, press the SEL button. Before trying to load paper, check to be sure that you have the paper lever in the correct position (BOT, TOP, REAR) for the path that you are using.

CAUTION:

Always power OFF the printer before you turn the platen knob.

If the paper lever is in the correct position and you are using rear feed, lift up the paper separator and check to be sure that the paper is properly on the tractors and has not jammed.

If the paper lever is in the correct position and you are using the optional bottom-feed push tractor, check the bottom tractor unit to be sure that the paper is properly installed on the tractors and that the paper has not jammed.

Once the paper is correctly loaded, press and release the SEL button, then hold the SHIFT button and press the RESET (Character Pitch) button.

11. Word processor files do not print the way the MENU and front panel are set.

Before sending a file to the printer, many word processors send either an initialization string or an I-Prime signal to the printer.

The initialization string contains codes that reset the printer to a default set of features. Otherwise, the printer might accidentally print using features set for a previous job. These codes will override the panel or MENU settings. To set your printer to ignore the reset codes, enter the printer MENU (hold down the SHIFT button while pressing SEL/MENU button) and change the Reset Inhibit item (in the Setup Group) to Yes. Please note that while this will stop the reset code from resetting your printer, but other codes in

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Contents ML520 // ML521 Dot Matrix Printers About This ManualService 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 MicrolineProduct Specifications Power RequirementsAmbient Temperature and Relative Humidity RH AltitudeProduct Specifications Agency Approvals 1.5.01 Listings IPS CPI CPSHoriz. DPI Vert. DPI HSDUPC a UPC E EAN Emulations Front Panel SwitchesGraphics Resolution Fonts Near Letter QualitySelects Group Function Menu Mode Switch ActionLine Feed Increments Fixed Form Feed / Load Selects ItemPaper Tear Capabilities Paper LoadingPaper Out Detection Print Method Printhead Type General InformationAuto Gap Printhead Gap AdjustmentGap Control Semi Auto GapPrint Modes 80 12 cpi 320 12 cpi 427 12 cpiContinuous Form Paper SpecificationsTypes Card Stock Cut SheetLabels EnvelopesTransparency Number of Copies WeightLength ThicknessPaper WidthPrinting Area Eprom Memory SpecificationsEeprom 03 RAMProduct 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 UtilityReliability Principles of Operation Electrical OperationPrinciples 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 InitializationPrinciples 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 TimeService 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 greaterPrinciples of Operation Head Overheat Alarm Processing Principles of Operation Power Supply Circuit Voltage/Signal PurposeService 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 MechanismPage Principles of Operation Ribbon Drive Operation Page Change Lever Paper Path Selection Lever Principles of Operation Line Feed MechanismPaper 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 DetectionPage Principles of Operation Support Protector Mechanism Principles of Operation Automatic Paper Load Cut Sheet PaperPrinciples of Operation Continuous Feed Paper Principles of Operation Paper Park Paper Park OperationMaintenance & Disassembly General Information Maintenance & Disassembly Maintenance Tools Maintenance & Disassembly Maintenance Precautions Handbook when the any of the following occurService Guide ML520/521 Maintenance & Disassembly Preliminary Items Page Maintenance & Disassembly Printhead Assembly Perform this procedurePage Perform these procedures 3.2.01 , Maintenance & Disassembly Ribbon Protector53562801 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 InstallationPage 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 HandbookPage 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.2.04Maintenance & Disassembly Right Ground Plate 51010201 Plate Right Ground Rspl Both B.2.05Perform 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 HandbookPage 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.2.05Maintenance & 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 Parallel Adjustment Phase Printhead Gap Modification PhaseVerification Phase Page Maintenance & Disassembly Key Combinations Description SEL + FF/LOADMenu Mode Printing the MenuProcedure Reset Menu to Factory DefaultsLimited Operation General Information Page Maintenance & Disassembly Menu Settings Group SettingValid Yes No Page Setting Top of Form Maintenance & Disassembly Top of Form General InformationReset the Top of Form to Factory Default Procedure Continuous Feed to Single Sheet Maintenance & Disassembly Paper Park General InformationProcedure Single Sheet to Continuous Feed Maintenance & Disassembly Tear Feature Maintenance & Disassembly Forms Tear Off Vertical Line Spacing ProblemsUsing Checking Top of Form with Form Tear Off ActivatedFactory default Top of Form Setting is 1 inch Cleaning Schedule Maintenance & DisassemblyCleaning Cleaning ToolsLubrication Types LubricationLubrication Schedule Lubrication AmountsAreas Not Lubricated Shipping Instructions Return for ServiceAll Other Returns Failure & Repair Analysis Introduction Service Guide ML520/521 Failure & Repair Analysis Firmware Revision Identification HeaderService Guide ML520/521 Failure & Repair Analysis Problem Lists Fax Number Failure & Repair Analysis Reporting Methods OkilinkCourse Critique Mailing AddressOkilink Technical Service BulletinsFaxable Facts Service Guide ML520/521 Operational Errors Failure & Repair Analysis Problem CategoriesAlarm Lamp Blinks Fatal Errors Alarm Lamp Lights Paper End/Jam ConditionsFailure & Repair Analysis Start Here Flowchart StartFailure & Repair Analysis Tips for Preventing Image Problems This Service HandbookFailure & Repair Analysis Common Problems Always power OFF the printer before you turn the platen knob Page Uneven Print Density Smeared Print Inconsistent Line FeedDrifting Margin Failure & Repair Analysis Left Margin Drifting Problem Fault Alarms Failure & Repair AnalysisAlar 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 TestPage Failure & Repair Analysis Serial Cable Information Service Guide ML520/521 Service Guide ML520/521 Example Hex Data DumpService 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 Description Board Designation Section Main Controller Board Chapter a Reference ChartsOperator Panel Board Chapter a Reference Charts Board Layout Fuses SwitchesFirmware JumpersPage 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 RememberRspl 521 520Both Placing a Parts Order Charts Chapter B Illustrated Parts Listing Overview Comments Refer toComments Refer to 53067201 2PA4094-7382G1 Cover Access Wide Rspl ROM PCB Leop Service Guide ML520/521 Page Service Guide ML520/521 Page Service Guide ML520/521 Page 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 BothComments Refer To B.1.02Service Guide ML520/521 Page Okidata P/N Oki-J Description Comments Refer Comments Refer
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