LG CG225 Service Manual page 62

Microphone Signal Flow
• MIC is enable by MICBIAS
• MICBIAS, MICP, MICN signals to ABB
Trouble Shooting Setup
• Initialize GSM MS test equipment.
• Connect PIF-UNION to the phone, and power on.
• Make a test call to 112.
• Make a sound in front of the microphone
MIC Bias
R215 MICN
MICP
MICN
Check Points
• Microphone bias
• Audio signal level of the microphone
• Soldering of components
Trouble Shooting Procedure
• Check the bias of the microphone.
• Check the audio signal path.
• Check the soldering.
• Check the microphone.
• Check the operation of FPCB
MICP
The waveforms at MICP and MICN
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4. TROUBLE SHOOTING
AC voltages
of the signals