Epson LQ-870 Service Manual page 112

Table 5-5. Repair of in the Main/Drive Circuit Board (Continued)
Problem Symptom
The printer The CPU does
not operate.
does not op-
erate at all.
The carriage The carriage
operates does not op-
abnormally. erate at all.
Carriage oper- IC152A is
ation is unsta-
torque).
Cause
Either ROM or
RAM is
defective.
The CPU is
Check the oscillator signal at either pin 33
defective. or pin 34 of the CPU.
Check the CR motor phase signal at pins
defective.
9, 10, 1 1, and 12 of IC2C.
At IC15, check the input signal for pin 6
defective.
and the output waveform for pin 8.
defective.
5-17
Checkpoint
REV.-A
Solution
Replace IC3A
or IC4A.
If a signal is
detected, re-
place IC2C.
Otherwise, re-
place CR 1.
Replace IC2C.
Replace IC 15.
Replace IC 15.