Epson FX-870/1170 - Manual (Page 149)

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
The CPU
at does not
on. operate
properly.
Cause
The reset
circuit is
defective.
Checkpoint Solution
Check the voltage waveforms of the VDD
(IC4 pin 41) and ROUT pin 15) when the
power is turned on.
The control Check HIGH/LOW alternation for the Replace
ROM is not signal pin 4).
selected.
the
ROM or the
RAM is
defective.
Replace IC2
or IC3.
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Epson