LG U300 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 → C537,C543 → R527,R534 → U504(amp) →
U503(Receiver/Speaker switch) → L500, L501 → CN602 → LCD FPCB → Speaker
Connect the phone to network
Equipment and setup call
Setup 1KHz tone out
Set phone with speaker Phone mode
The sine wave appear at
The sine wave appear at
The sine wave appear at
The sine wave appear at
Speaker side in FPCB
Can you hear the tone?
Start
NO
C537,C543?
YES
NO
R527,R534?
YES
NO
L500, L501?
YES
NO
YES
NO
YES
END
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Change the Main board
Check C537,C543,R527,R534 or
Change the Main board
Check U504,U503
Check the connector or
Change the FPCB
Change the speaker