LG U310 Service Manual page 115

4. TROUBLE SHOOTING
4.17.5 Microphone for Head_Set
MIC for Head_Set path as below:
Insert Headset -> EAR_SENSE_N(pin6) go 0V -> MSM6250A sense Head_Set insertion ->
MIC signal go to MSM(C216, C217) by through b-to-b connector
CN501
MMI_CONNECTOR
21
19
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
20
22
Try change the head set
EAR_SENSE_N is 0V?
R524
R526
C537 33u
0
C538 33u
0
C542 R529
1 2
IN OUT
3 4
G1 G2
NFM21PC105B1A3
Start
Make a call
NO
Yes
MIC_BIAS is 1.8V ?
Yes
Change the Main B'd
R521
VREG_MSMP_2.7V
51K
MIC2N
EAR_MIC2P
HPL_L
HPL_R
USB_D+
USB_D-
EAR_SENSE_N
VBATT
1K
PM_ON_SW_N
+5V_PWR
USB_VBUS
UART_TXD
UART_RXD
OK
END
NO
Check the CN501
NO
Change the Main b'd
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AUDIO
Near to MSM