to test pin 2, 6 of U603 and there is waveform input, check pin 1, 7 and waveform output is normal, so
we judge that the contact of headphone holder has trouble, after changing headphone holder, trouble is
removed.
Example 13
Symptom: no MIC
Analysis and troubleshooting: power on, use remote controller to switch on MIC, insert microphone
and speak, use oscillograph to test pin 4 of MIC board XS601 (OK) and find that there is no signal output,
check pin 4, 8 (+9V, -9V) of U601 and voltage is normal, use oscillograph to test pin 5 of U601 (4558)
and there is signal input, test pin 1 of U601 and there is no signal output, after changing U601, trouble is
removed.
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