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REV.-A
Table 5-6. Power Supply Circuit Unit Repair
Symptom
Cause
Check Point
Solution
The +5V dead. IC 1A is
Observe the oscillation waveform and the switching
Replace
IC 1A
defective.
waveform.
o
klllzk
IV/DIV, 20@DlV
Oscillation Waveform (pin 2 of IC 1A)
o
bllu
10V/DIV, 20ps/DIV
Switching Waveform (Pin 9 of IC 1A)
Transistors Q 12 Observe the chopping waveform Replace Q12 or
and Q 13 are
Q13.
defective.
o
U_u
IOV/DIV, 20/.Ls/DlV
Chopping Waveform (Emitter of Q13)
5-18