Repairingthe Boardassembly, C094Main - Epson FX 1170 - B/W Dot-matrix Printer Service Manual

REV.-A
5.4 Repairing the Board Assembly, C094 MAIN
This section provides instructions for repairing the BOARD ASSEMBLY, C094 MAIN. It describes various
problems, symptoms, likely causes, checkpoints, and solutions. The checkpoint column provides proper
waveforms, resistance values, and other information for each component of the C094 MAIN.
Table 5-5. Repairing the BOARD ASSEMBLY, C094 MAIN
Problem
Symptom
Abnormal The CPU
does not
power on. operate
properly.
Cause
Check the voltage waveforms of the VDD (+5
The reset
circuit is
defective. power is turned on.
1 I I I I I I
[
The control Check the signal HIGH/LOW alternation (IC4
ROM is not pin 4).
selected.
Either the
ROM
or the
RAM
is
defective.
Checkpoint
-1-
1 I [1
+
1
5-14
Solution
Replace IC4.
1 I I I I 1 II I I I
1
Replace IC4.
1
Replace IC2
IC3.
or