LG 42LY750H Service Manual page 23

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 JK3301/JK3302/JK3303
Can you see the normal waveform?
Y
Check Audio AMP output
L5402,L5403,L5404,L5405
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 JK3301, JK3302, JK3303
N
Replace
L5402,L5403,L5404,L5405
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