LG KC550 Service Manual page 106

6.12.2 Power circuit
VRF3_2V85
47nH
L101
C111
12p
C122
120p C123
0.01u
VRF2_1V5
VSD2_1V8
VSD1_1V5
C129
C130
0.1u
C131
0.1u
0.1u
VBAT
BAT_ID
RF_TEMP
REMOTE_ADC
√ Output voltage (=LDO output of U102)
- check LDO output voltage of U102
→ I.e. VRF1_2V85 (C125),
VRF2_1V5 (C118),
VRF3_2V85 (C121)
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
Power Circuit
Check Voltage of TP1,
TP2 & TP3.
Is it correct?
YES
Power is OK.
See next part.
Fig 2 Debugging flowchart of Power circuit
VRF3_2V85 VRF3_2V85 VRF3_2V85
VRF3_2V85 VRF3_2V85
VRF1_2V85
47nH
L102
C112
C116 C117
C115
C113 C114
0.01u 0.01u
100p
0.01u
0.1u 0.01u
H3
M0
J3
M1
G4
M2
H4
M7
G3
M8
J4
M9
F4
M10
W3
Fig 3 Power circuit (U104)
NO
Replace PCB
TP3
VUSB_3V1
VAUDIO_2V5
VBAT
VAUX_2V9
C102
1u
VVIB_2V8
C101
C103
2.2u
1u
C110
1u
C108
VMMC
2.2u
C119
VIO_2V62 VRF1_2V85
2.2u
VRF3_2V85
C124
C121 C125
1u
1u
TP102
2.2u
TP3
TP1
TP2
- 107 -
6. Trouble shooting
VRF2_1V5
VPLL_1V5 KDR331V
TP2
R104
2
R105
3
1
D101
C118
1u 2.2u C109
VRTC_2V0
C120 0.1u
VBAT VSIM_2V8
TP1
VBAT
C126 C127
220n
1u
C128 220n
LGE Internal Use Only
OVP_VCHG
0
OVP_VUSB
0