LG C1150 Service Manual page 76

Checking Flow
SETTING : After initialize Agilent 8960, Test EGSM, DCS mode
START
Voltage across C141
= 2.5VDC?
MIC Bias Voltage
Yes
Check the signal level
at each side of MIC101.
Is it a few tens mVAC?
Yes
Check the soldering of
R127,R130, R132,
Yes
Replace Main board.
MIC WILL WORK.
Waveform
MIC+
MIC-
Voltage VMIC of U102
No
= 2.5VDC?
Yes
Resolder R123 & R125.
Replace the microphone, MIC101.
No
Resolder R127,R130, R132.
No
Graph 4-11
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4. TROUBLE SHOOTING
Replace U102.
No