LG U8290 Service Manual page 127

4. TROUBLE SHOOTING
Receiver Path for Head_set
Voice Receiver & video telephony path for Head_Set as below:
MSM6250 HPH_R, HPH_L → C626, C627 → CN304(Head_Set Jack)
Start
Conne ct the phone to ne twork
Equipment and setup call
Setup 1 KHz tone out
An d in sert head_Set
EAR_SENSE*(R624) is 0V?
The sine wave appear at
C626, C627?
The sine wave appear at
CN304 pin 4,5?
Can you hear the tone ?
END
NO
YES
NO
YES
NO
YES
NO
YES
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Change the Main board
Change the Main board
Check C626, C627
Change the Head_Set