LG DK763X, Service Manual

Page: 13 / 51

3-2
ELECTRICAL TROUBLESHOOTING GUIDE
1. Power check flow
No 3.3VA
Replace the FR101
(Use the same ICW) Is the FR101
Normal?
Is the Vcc (about 8.7V)
supplied to IC101 Pin2?
Is the D105/ D106/
D107/ D108 Normal?
NO
NO
NO
NO
NO
NO
NO
Replace the D105/
D106/D107/D108
Check or Replace
the IC101
Replace the D121
Replace the IC103
Replace the D123
Replace the D125
YES
YES
YES
YES
YES
YES
Is the D121
normal?
YES
YES
Is there about 2.5V
at the IC103 Pin1?
Is the D123
normal?
Is the D125
Normal?
Power Line of Main
PCB(DVD) is short
No 12V
Check or Replace
the D125 Is the Vcc(=14V) sup-
plied to Q123 Collector?
Check or Replace
the Q123
Is the Vcc(=12V) sup-
plied to Q126 Base?
NO
NO
Check the ‘PWR CTL
“H”’ signal from µ-com
YES
YES
YES
No REG 5.0V
Check or Replace
the D123 Is the Vcc(=5.6V) sup-
plied to Q126 Collector?
Check or Replace
the Q126
Is the Vcc(=12V) sup-
plied to Q126 Base?
NO
NO
Check the ‘PWR CTL
“H”’ signal from µ-com
YES
YES
YES