LQ-670 Service Manual
Rev. A 5-1
3
Symptom Condition Cause Checkpoint Solution
Normal voltage is
not output. All the output
voltage is
defective
+42V
stabilization
circuit is
defective.
Check the waveform of 1pin in the
Photo coupler PC1. If it is unloaded,
the waveform with periodical pattern
can be seen.
•If the waveform is abnormal, the
elements around PC1, ZD51,
ZD81∼85, or peripheral elements
are defective.
•If the wavaform is normal, check
the switching waveform of Q1, Q2,
Q3 and also check the operation of
peripheral elements and Q1/Q2/Q3.
Figure 5-10. Waveform of PC1
Replace the
power supply
board or
appropriate parts.
+5V output is
abnormal,
+35V output
is normal.
IC51 is
defective. Check output voltage at 9,10 pin of
IC51.
•If output is abnormal, IC51 is
defective.
Replace the
power supply
board, IC51 or
peripheral
elements.
Smoothing
circuit is
defective.
Check if the normal voltage
(about+5V) is provided between +/−
terminals of C54. If there is no
output, L51 or C54 is defective.
Replace the
power supply
board, L51 or
C54.
Table 5-10. Repairing the C214PSB Board (Con.)