Read LG 42LT777H (CHASSIS:LA2FZ) Service Manual online
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Composite Video Trouble Shooting guide
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 JK3800
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.
Replace JK3800
N
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, R3308, R3309, R3328, R3329 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.
Replace JK3301, JK3302, JK3303
N
Replace IC100
N
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