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Service Guide ML520/521
Chapter 4 Failure & Repair Analysis
Left Margin Drifting Problem
NOTE:
This information is also provided in Technical Service Bulletin 1707.
To correct a problem with the left margin drifting during print operations, follow this procedure.
1. Manually slide the carriage assembly back and forth along the full length of the carriage shaft.
Check for "drag" caused by the ribbon, a dirty space rack, or other obstructions.
If you suspect that the ribbon is causing movement problems, check the movement of the carriage
assembly with the ribbon removed
OR
with a new ribbon installed.
2. Check the contact between the carriage frame and the space motor board assembly.
Contact is made at the front edge of the board.
Any gap will keep the space motor gear from fully engaging with the space rack. This will result in
slippage problems, which will affect spacing operations.
3. Check the printhead cable connections between the main control board and the space motor. Solid
contact
MUST BE
made at all connections or print problems will occur.
4. Check the condition of the printhead cable. If it is broken, torn, or sharply bent, replace the cable.
5. If the problem continues, check the parts listed below (in the order given). Replace the suspected
part. Be sure to test the printer after replacing each part.
1. Carriage: Frame Set
2. Motor: Space
3. Rack: Space
4. Cable: Printhead
5. Board: Main Control
6. If the problem continues, check all assemblies and connections. Then, contact Okidata Technical
Information for further assistance.
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)