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Service Guide ML390/391
Chapter 4 Failure & Repair Analysis
RAP 01: Operator Panel Lamps Do Not Light
START
Are the AC cables connected correctly?
NO Connect the AC cables correctly.
Is the problem resolved?
YES End of procedure.
NO Go to A
YES Go to A
A
Check the AC fuse on the primary side of the filter assembly. Is it open?
YES Replace the fuse
Is the problem resolved?
YES End of procedure.
NO Go to B
NO Go to B
B
Verify that the fuse holder is making proper contact with the fuse. Remove the fuse from the holder. Gently
squeeze both sides of the holder slightly towards each other. Reinsert the fuse. Is the problem resolved?
YES End of procedure.
NO Are + 5 vdc and + 40 vdc supplied to the control board?
+ 5 vdc Take the voltage reading between Pin 6 and Pin 9 of CN2 on the power supply board.
+ 40 vdc Take the voltage reading between Pin 1 and Pin 5 of CN2 on the power supply board. Meter
should read + 40 vdc.
YES Replace the control board.
YES End of procedure.
NO Go to C
NO Go to C
C
Check the fuse on the power supply board. Is it open?
YES Replace the fuse.
Is the problem resolved?
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