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Principles of Operation
Repairing
the C094 MAIN Board Assembly
-
This section gives instructions for repairing the C094 MAIN board and describes various problems,
symptoms, likely causes, checkpoints, and solutions.
The checkpoint column shows proper
waveforms, resistance values, and other information for each component of the C094 MAIN board.
Table 6-8. Repairing the C094 MAIN Board Assembly
Problem Symptom
4bnormal
The CPU
weration at does not
rower
on.
operate
properly.
Cause
The reset
circuit is
defective.
-
Checkpoint
Solution
Check the voltage waveforms of the VDD
(+5
V)
Replace
Ic4
(IC4 pin 41) and ROUT
(IC4
pin 15) when the
power is turned on.
The control
Check HIGH/LOW alternation for the
Replace
ROM is not
signal
(IC4
pin 4).
IC4.
selected.
Either the
ROM or the
RAM is
defective.
Replace IC2
or IC3.
6-34
Epson
PX-870/1170