Repairing The Main Board - Epson LQ-670 Service Manual

LQ-670 Service Manual

5.4 Repairing the Main Board

Refer to the following table for repairing the main board.
Symptom Condition
The printer does Reset signal is
not work at all. not canceled.
CPU does not
work.
5-14
Table 5-11. Repairing the C214 Main Board
Cause
Defective
operation of the
reset circuit
VOUT signal is
output.
Clock signal is
not generated.
PROM(IC8) or
Flash
ROM(IC7) is
defective.
Checkpoint
After the power is turned on,
check 1pin of IC12 stays
LOW for a while.
Reset signal is generated in
the IC21 and sent to the
CPU and gate array.
Check if +5V is normal and
also check pin 7 and pin 8 of
CN3.
Check the signal of pin 26
and 27 in the IC11 (clock
signal of CPU)
Figure 5-11.Clock Signal of
CPU
Check the waveform of 22
pin of IC 7 or IC8.
If there is no waveform,
gate array(IC10) is defective.
Figure 5-12. Chip Select
Signal
Solution
Replace the main
board.
Replace the
power supply
board
Replace the main
board or CRU1.
Replace the main
board.
Rev. A