LG U310 Service Manual page 111

4. TROUBLE SHOOTING
4.17.3 Loud Speaker path(voice speaker phone, VT, multimedia play, etc)
Loud speaker path as below:
MSM6250A AUXOP_AUXOL, AUXOP_AUXOR -> C530,C540 -> R515,R528 -> U508(amp) ->
U507(Receiver/Speaker switch) -> R514, R522 -> CN602 -> LCD FPCB -> Speaker
Connect the phone to network
Equipment and setup call
Setup 1KHz tone out
Set phone with speaker Phone mode
Can you hear the tone?
Start
The sine wave appear at
C530,C540?
YES
The sine wave appear at
R515,R528?
YES
The sine wave appear at
R514, R522?
YES
The sine wave appear at
Speaker side in FPCB
YES
YES
END
NO
Change the Main board
NO
Check C530,C540, R515,R528 or
Change the Main board
NO
Check U508,U507
NO
Check the connector or
Change the FPCB
NO
Change the speaker
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