Read LG 42LH70YD (CHASSIS:LJ91D) Service Manual online
4. Analog TV Video Trouble Shooting
Check RF Cable
Y
Check CVBS Signal
TU101 #7 Pin and R118
N
Y
Check CVBS Signal
R703 and C110 at Main Baord
N
Replace one of R703 and C110
& Recheck
Y
Y
Maybe Tuner(TU101) has problems
Check Tuner(TU101) Power
(5.0V, 2.5V, 3.3V, 1.2V)
N
Maybe BCM3556(IC100)
has problems
Check cable between P203 at Jack
Board and P701 at Main Baord
N
Maybe Cable Pin has problems
Y
Replace one of IC101, IC102 at
Jack Board or IC803/ Q812/ IC804/
IC809/Q809/+5V_ST and +12V of
P801 at Main Board& Recheck
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