Epson FX-870 Service Manual page 151

Principles of Operation
Table 6-8. Repairing the C094 MAIN Board Assembly (Continued)
Problem Symptom
Self-test The printer
printing does not print defective.
abnormal the self-test.
Self-test
A particular
printing
dot fails to
abnormal.
print.
6-36
Cause
IC4 is Check the head pulse signal at pin 31 (input)
and pin 63 (output).
One of the Check the head drive signal at the base and
head driie the emitter of each transistor.
transistors
is defective
6, 8, 9, 10,
11, or 12).
Checkpoint
Solution
Replace IC4.
If the signal
at the base
is normal,
replace the
transistor.
Otherwise,
replace IC4.
Epson PX-870/1170