LG 40LX770H Service Manual page 20

3. Analog RF Video Trouble Shooting guide
Check RF cable & signal
YES
Check TU8900 Pin5(Video output)
Can you see the normal signal?
YES
Check tuner 5V power L8906
YES
Check tuner 3.3V power L8904
Check tuner 1.8V power L8907
YES
Check Mstar LVDS output
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Only for training and service purposes
NO
Could you measure voltage of TU8900 & IIC lines?
Are they all normal?
You should replace TUNER.
NO
Check IC2304
YES
NO
Replace L8904
NO
Replace L8907 or IC8900
NO
Replace Main IC(IC101) or main
board
YES
NO
Replace IC2304
Replace L8906
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NO
You should check power line
& IIC lines.
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