Repair Of The Main Board - Epson LQ-1070 Service Manual

REV.-B

5.3 REPAIR OF THE MAIN BOARD

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