Troubleshooting Flow Chart - Oki ML421 Maintenance Manual

6.5

Troubleshooting flow chart

1 Power is not supplied.
Is the AC cable connected correctly?
Yes No
Connect the AC cable correctly.
Is fuse F1 on the transformer assy/or F1 on the Power Supply Board blown?
No Yes
Replace fuse (with same type and rating).
Remedied?
No
Does DC + 50V out?
No Yes
Remove Printhead. (Turn power off, then on.)
Remedied?
No
Replace carriage cable or ribbon feed mechanism.
Remedied?
No
Replace Control Board.
Remove CN3 on Power Supply Board.
Measure for any short circuits between + 5V, + 50V, +12V, -8V, 0V in CN2 of Control
Board.
Any short circuit?
No Yes
42113901 Rev.2
Yes
End
Yes
End
Yes
End
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