3.4 REPAIRING THE POWER SUPPLY BOARD
This section provides instructions for repairing a defective power supply
board assembly. It describes various symptoms, likely causes and
checkpoints. Refer to proper waveforms, resistance and other values
shown in the tables when evaluating the operation of any potentially faulty
component. Check these value and take the appropriate action.
WARNING
The
OPERATE
switch on the operation panel only
turns the secondary power circuit on or off, so the
primary circuit is live as long as the printer is
connected to AC power outlet. Before, you repair
or touch the power supply board, be sure to
disconnect the AC power outlet.
CAUTION
This information is necessary only for servicers
who repair to the component level. Servicers who
repair to the unit level (including all servicers in
the U.S.) can ignore this section.
Table 3-7. Repairing the Power Supply Board
Problem Cause Checkpoint Solution
+35V and
+5V lines
are not
output
when the
printer is
power on.
The diode
bridge DB1
is failure.
Measure the DC voltage between
the pin 3 and 4 of DB1.
Replace
DB1.
The
transformer
T1 coil is
open.
Measure the resistance of T1
coils at pin 12 - 15, 9 - 11, 7 - 8 or
3 - 4.
Replace
T1.
Table 3-8. Repairing the Power Supply Board (Continued.)
Problem Cause Checkpoint Solution
+35V
and +5V
lines are
not
output
when the
printer is
power
on.
Switch-
ing FET
Q1 is
failure.
• Check the resistance between
SOURCE and DRAIN is infinite.
• Check the voltage waveform between
SOURCE and DRAIN of Q1.
Figure 3-8. Waveform 1
Replace
Q1.
PC1 is
failure.
Check the waveform between pin 3
and 4.
Figure 3-9. Waveform 2
Replace
PC1.
Q32 is
failure.
Check that the resistance between
COLLECTOR and EMITTER is infinite.
Replace
Q32.
Q31 is
failure.
Check that resistance between
SOURCE and DRAIN is infinite.
Replace
Q31.
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