LG 47LH90 Service Manual page 51

LA92B-LH40/LH55 Trouble shooting guide – SPDIF
Check the output (Pin E9) of LGE3159(IC100).
Measure waveform at R159 because it's more easy to check.
Can you see the normal signal?
YES
Check the input of JK601.
Can you see the normal waveform?
YES
After checking the Jack, you should decide to replace item or not.
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Only for training and service purposes
NO
This board has big problem because Main chip(LGE3159) have some troubles.
After checking thoroughly all path once again, You should decide to replace LGE3159 or not.
NO
After checking audio signal line, you should decide to replace item or not.
Audio(Out)
LGE Internal Use Only