Audio Troble - LG -E400f Service Manual

4.18 Audio Troble

4.18.1 Receiver Path
MSM75A EAR1_OP, EAR1_ON → RCV_P, RCV_N → R70, R703 (TP3) →
M700 (TPA055D3: Audio Subsystem) → FB705, FB706 (TP2) → CN700 (TP1) (Antenna + SPK pad)
Connect the phone to network
Can you hear the 1KHz TONE?
Change the U00 (MSM75A) or
LGE Internal Use Only
START
equipment and set-up call.
Set-up 1KHz tone out.
No
The sine wave appears at
CN700 (TP1) ?
No
The sine wave appears at
FB705, FB706 (TP)?
No
The sine wave appears at
R70, R703(TP3)?
No
Change the main PCB
Yes
END
Yes
Re-contact or Change the SPK/RCV
module
Yes
Change the SPK/RCV module
Yes
Change the M700 (Audio Subsystem)
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4. TROUBLE SHOOTING
Only for training and service purposes