Specifications

REV.-B
5.3 REPAIR OF THE MAIN BOARD
This section provides instructions for repairing the BOARD ASSY., MAIN when it is defective and
describes various symptoms, likely causes, and checkpoints. Checkpoints refer to proper waveforms,
resistance values, and other values to be checked to evaluate the operation of any component that might
be bad. Check these values and take the appropriate action.
Table 5-4. Repair of a Problem’in the BOARD ASSY., MAIN
Problem
Symptom
Cause
Checkpoint Solution
The printer The CPU does The reset cir-
Check the voltage waveforms for the + 5V Replace IC2A.
does not op- not operate. cuit is not
line (IC2A pin 52) and for the THLD signal
erate at all. operational.
(IC2A pin 73) when power is on.
Check the voltage waveforms for the
Replace IC4D.
THLD signal (IC2A pin 73) and for the
RESET signal (IC4D pin 4) when power is
on.
Check pin 2 1 of ICl C for a HIGH Vx Replace IClC.
voltage (NMI signal).
Selection of
Check pin 36 of IC4D for a change in the Replace IC4D.
control ROM
signal HIGH/LOW.
is abnormal.
5-14