LG KC780 Service Manual page 94

5.12.2 Power circuit
VRF3_2V85
47nH
L101
C111
12p
0.01u
C122
R109 1
VRF2_1V5
VSD2_1V8
VSD1_1V5
C128
0.1u
C129
0.1u
VBAT
BAT_ID
RF_TEMP
TP105
REMOTE ADC
Output voltage (=LDO output of U104)
- check LDO output voltage of U102
I.e. VRF1_2V85 (TP1), VRF2_1V5 (TP2), VRF3_2V85 (TP3)
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
100p 0.01u 0.01u
0.01u
0.1u 0.01u
H3
M0
J3
M1
G4
M2
H4
M7
G3
M8
J4
M9
F4
M10
Fig 3 Power circuit (U104)
TP3
TP1
NO
Replace PCB
TP3
VUSB_3V1
VAUDIO_2V5
VBAT
VAUX_2V9 C102
VPLL_1V5
1u
VVIB_2V8
C101
C103
2.2u
1u
C110
1u
C108
VMMC
2.2u
C119
VIO_2V62 VRF1_2V85
2.2u
VRF3_2V85 VBAT
C123
C121 C124
1u
1u
TP102
2.2u
TP2
- 95 -
5. TROUBLE SHOOTING
TP2
VRF2_1V5
KDR331V
OVP_VCHG
2
3
OVP_VUSB
1
D101
C118
1u 2.2u C109
VRTC_2V0
C120 0.1u
VSIM_2V8
TP1
VBAT
C125 C126
220n
1u
C127 220n
LGE Internal Use Only