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Principles of Operation
Component Repair Information (for Dealers Outside the U.S.)
This portion of the manual provides additional information for servicers outside the U.S. who need
to make repairs to components on the circuit boards. (U.S. service technicians can ignore these
pages.)
Repairing the C076 PSB Board Assembly
This section gives instructions for repairing the C076 PSB board assembly. It describes various
problems, likely causes, checkpoints, and solutions.
The checkpoint column provides proper
waveforms, resistance values, and other information for each component of the C076 PSB.
WARNING
The OPERATE button on the control panel only turns the secondary power circuit on or off, so
the primary power circuit is live as long as the printer is connected to an AC power outlet.
Do not touch the heat sink attached to the FET (Ql) when the printer is powered.
Table 6-7. Repairing the C076 PSB Board Assembly
Problem
Cause
The
+35
V line is Diode bridge
DBl
Sad.
1
is bad.
The transformer
coils are open.
Measure the resistance of the
Tl
transformer coils
at pins 3-2, 5-4, 1 O-l 1, and 11-9.
Ql
is bad.
*
Check the voltage waveforms at
Ql.
Checkpoint
Measure the DC voltage between pins 3 and 4 of
DBl
.
CH1=50V TIME=2ps
I
I
I I
Solution
qeplace
IBl.
qeplace
Tl
.
qeplace
Ql
.
Epson
FX-870/1170