Read LG 42PT350B-SG (CHASSIS:PB12K) Service Manual online
4. Analog TV Video Trouble Shooting
Check RF Cable
Y
Check CVBS Signal
TU1300 #11 Pin
N
Y
Check CVBS Signal
R1334
N
Replace one of
R1330/Q1305/R154/C213
& Recheck
Y
N
Y
Check Tuner Power
(5.0V, 3.3V, 1.2V)
Replace one of
L506/L509/IC600
& Recheck
Maybe Tuner(TU1300) has problems
Maybe Mstar S7LR(IC101)
has problems
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