LG P705 Service Manual page 105

4.19.6 Headset micr ophone
MIC Signal: 3.5 pi Headset (J900) → FB710(TP4) → C213(TP4) EAR_MIC(MIC2P) of MSM7227A-1-AA
MIC Bias : VREG_MSME_1.8V → R722 (TP1) (DET) → R723(TP3)(RES) -> Headset MIC
HS Detect IC Bias: VREG_P3_2.85V
R722(TP1) is about 1.8V & C751(TP2)
R723(TP3) is about 1.2~1.4V?
Make a some sound or voice to MIC
Some sound signal appears at
Some sound signal appears
Change the U200(MSM7227A-1-AA) or
Change the Main PCB.
LGE Internal Use Only
START
Make a call
is about 2.85V?
Yes
Yes
FB710(TP4)
No
at C213(TP5)
No
No
Change the Main PCB.
No
Change the U705(MAX14579E) or
change the Main PCB.
Yes
Change the Headset or Re-solder/
change the J900.
Yes
Re-contact or test the new Upper
FPCB.(If It's OK, change the FPCB)
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4. TROUBLE SHOOTING
Only for training and service purposes