LG FH2 Service Manual page 34

ELECTRICAL TROUBLESHOOTING GUIDE
NO AUDIO OUTPUT
MIC function
Check IC105 pin78(3.3 V)
after inserting MIC.
Check MIC signal L35.
Check IC5 pin3(5 V), pin4(3.3 V).
END
YES
YES
YES
YES
NO
Check R15, R42, L326, JACK301.
NO
NO
Check L38, L40, IC5.
3-17
Check IC4.