Read LG 42LT777H (CHASSIS:LA2FZ) Service Manual online
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Composite / RGB-PC Audio in Trouble Shooting guide
HDMI Audio in 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 C345, C346, C319, C320 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 Audio AMP output
L5402,L5403,L5404,L5405
Replace L5402,L5403,L5404,L5405
N
Y
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
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
Check Audio AMP output
L5402,L5403,L5404,L5405
Replace
L5402,L5403,L5404,L5405
N
Y
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