LG 42LY750H Service Manual page 21

AV Video Trouble Shooting guide
Check input signal format.
Is it supported?
Y
Check AC cable for damage
For damage or open conductor
Y
Check JK3601
Can you see the normal waveform?
Y
Check the input of MTK(IC105).
Measure waveform at C360 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.
HDMI Video Trouble Shooting guide
Check input signal format.
Is it supported?
Y
Check AC cable for damage
For damage or open conductor
Y
Check JK3301/JK3302/JK3303
Can you see the normal waveform?
Y
Check HDCP key NVRAM(IC100)
Power & I2C signal
Y
Check the input of MTK(IC105).
Measure waveform at R3314, R3315, R3328, R3329, R3308, R3309 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.
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Only for training and service purposes
N
Replace JK3601
N
Replace JK3301, JK3302, JK3303
N
Replace IC100
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