LG 28LJ400B Service Manual page 22

Standard Repair Process
Error
LED TV
symptom
1 Power Supply Trouble
A1. Power Supply Trouble
No power
Check Pin1 2 of CNB2 for 12V
N
Check if the power
board is OK?
N
Repair the power board.
Repair the abnormal circuit :
1.5V_STB—check U2
2. 3.3V_STB—check UL1
3.+1.15V–- check UD1
and peripheral components
Repair the abnormal circuit :
1. . 5V_M heck power supply ,and
QM32 circuit
2. . CC_DDR–- check UL1
Established
date
Revised date
Y
Check power on the TV board.
Y
Check U2 for 5V_STB , UL1 for
3.3V_STB and UD1 for +1.15V_STB
Y
N
Power on , check QM32 for
5V_M,UL1 for VCC_DDR
N
Y
OK
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