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Principles of Operation
Table 6-8. Repairing the C094 MAIN Board Assembly (Continued)
Problem Symptom Cause
Checkpoint
Solution
Self-test
The printer IC4 is
Check the head pulse signal at pin 31 (input)
Replace IC4.
printing
does not print defective.
and pin 63 (output).
abnormal the self-test.
Self-test
printing
abnormal.
A particular
dot fails to
print.
One of the Check the head drive signal at the base and
If the signal
head driie the emitter of each transistor.
at the base
transistors
is normal,
is defective
replace the
(QZ
4,5,
transistor.
6, 8, 9, 10,
Otherwise,
11, or 12).
replace IC4.
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-
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6-36
Epson
PX-870/1170