LG 42LT777H Service Manual page 24

RGB-PC Video Trouble Shooting guide
Check input signal format.
Is it supported?
Y
Check AC cable for damage
For damage or open conductor
Y
Check JK3603
Can you see the normal waveform?
Y
Check the input of MTK(IC105).
Measure waveform at R323, R324 because it's more easy to check.
Can you see the normal waveform?
Y
This board has big problem because Main chip (MTK) have some troubles.
After checking thoroughly all path once again, You should decide to replace MTK or not.
Analog RF Audio Trouble Shooting guide
Check RF cable & signal
Check TU8900 Pin2
(SIF output)
Y
Check Audio AMP output
L5402,L5403,L5404,L5405
Y
Check IC5400
Y
Check C352
(SIF signal to IC105)
Y
Replace IC105
Copyright © LG Electronics. Inc. All rights reserved.
Only for training and service purposes
N
Replace JK3603
N
Replace Tuner
N
Replace L5402,L5403,L5404,L5405
N
Replace IC5400
- 24 -
LGE Internal Use Only