LG U990 Service Manual page 124

4.12.2 Voice path for headset
Voice path for Head_Set as below:
MSM6280 HPH_R, HPH_L → C548,C549 U502(audio codec) → C578,C562 → R529,C522 →
U504(Headset AMP) → FB502, FB503 → R525, R524 → #4, #5 pin of CN500 headset Jack
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
Start
Connect the phone to network
Equipment and setup call
Setup 1KHz tone out
And insert head_Set
Headset insertion detection
in the Main LCD Display OK?
YES
The sine wave appear at
C548,C549 ?
YES
The sine wave appear at
C578,C562 ?
YES
The sine wave appear at
R525,R524 ?
YES
Can you hear the tone?
YES
END
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4. TROUBLE SHOOTING
NO
Check #8 pin of CN500
or change the Main bíd
NO
Change the Main board
NO
Check the U502
or change the Main bíd
NO
Check the U504
or change the Main bíd
NO
Check the CN500 or change the
Main bíd
LGE Internal Use Only