Epson LQ 1050 Technical Manual - Page 175
klllzk, 10V/DIV
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REV.-A Table 5-6. Power Supply Circuit Unit Repair Symptom The +5V dead. Cause IC 1A is defective. Check Point Observe the oscillation waveform and the switching waveform. Solution Replace IC 1A o klllzk IV/DIV, 20@DlV Oscillation Waveform (pin 2 of IC 1A) obllu 10V/DIV, 20ps/DIV Switching Waveform (Pin 9 of IC 1A) Transistors Q 12 and Q 13 are defective. Observe the chopping waveform Replace Q12 or Q13. o U_u IOV/DIV, 20/.Ls/DlV Chopping Waveform (Emitter of Q13) 5-18
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