Specifications

I
REV.-B
5.3 REPAIR OF THE MAIN BOARD
This section provides instructions for repairing the BOARD
describes various symptoms, likely causes, and checkpoints.
ASSY., MAIN when
Checkpoints refer to
it is defective and
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
does not op-
erate at all.
The CPU does
not operate.
The reset cir-
cuit is not
operational.
Selection of
control ROM
is abnormal.
Check the voltage waveforms for the
+5V
line (IC2A pin 52) and for the THLD signal
(IC2A pin 73) when power is on.
Check the voltage waveforms for the
THLD signal (IC2A pin 73) and for the
RESET signal
(IC4D pin 4) when power is
on.
Check pin 21 of ICIC for a HIGH Vx
voltage
(NM I signal).
Check pin 36 of IC4D for a change in the
signal
HIGH\LOW.
Replace
IC2A.
Replace IC4D.
Replace IC 1 C.
Replace IC4D.
5-14