LG 47LH90 Service Manual page 47

LH40/LH55 Trouble shooting guide – TV/CATV
Check TU1 Pin16(SIF)
Can you see the normal signal?
YES
Check the input (Pin W2) of LGE3159((IC100).
Measure waveform at C147 because it's more easy to check.
Can you see the normal waveform?
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Only for training and service purposes
NO
Could you measure voltage of TU1001 & IIC lines?
Are they all normal?
YES
You should replace TUNER.
NO
After checking audio signal line, you should decide to replace item or not.
Audio(In)
NO
You should check power line
& IIC lines.
LGE Internal Use Only