Power Supply Board Unit Component Repair - Epson DFX-8000 Service Manual

Troubleshooting

Power Supply Board Unit Component Repair

Table 5-3. Power Supply Board Unit Component Repair
Problem
Symptom
Voltage is not
output correctly.
blown right after
replacement.
None of the
output voltages
are normal.
normal.
5-14
Cause
Checkpoint
The line filter Check if any of Cl - C7 or
circuit element is
bad.
The rectifier
Check if DBl has shorted or
circuit element is
bad. connected between the
positive and negative
terminals of DBl , C9, Cl 0,
shorted.
When DBl shorts, it may
l
be caused by a short in a
latter stage of DBl.
Verify that approximately
bridge) is bad.
300V of DC voltage is output
between the positive
terminal (pin 3) and the
negative terminal (pin 4) of
The output voltage of
l
due to
element in a latter stage
of DBl.
The surge
Measure the AC voltage
protection circuit between DBl pin 2 and L2
is bad. pin 4, and verify that it is
approximately OV.
. Either TYl is bad or any
of the components (R4,
C8, Dl, or Tl) that switch
Observe the drive
waveforms of the switching
transistors at ICl pin 8 and
pin 11 (see Figure 5-l 1 ).
The drive waveforms of
l
pins 8 and 11 have a
phase difference, but the
signal levels are the
same.
When DTC (pin 4) is
l
at a logical high (more
than 3.5V), the drive
waveforms are not
output.
Solution
Replace the
abnormal
element(s).
Replace DBl
and the
abnormal
element(s).
Replace DBl
and the
abnormal
element(s).
a
problem with an
Replace lY1
and the
abnormal
element(s).
Replace ICl .