Read LG 42LC7D (CHASSIS:LB73A) Service Manual online
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TROUBLESHOOTING
Check TU800 Pin8(Video output)
Can you see the normal signal?
YES
Could you measure voltage of TU800 & IIC
lines?
Are they all normal?
You should replace TUNER.
YES
NO
Check the input(Pin63) of AV switch(IC603).
Can you see the normal waveform?
YES
Check the output(Pin56) of AV switch(IC603).
Can you see the normal waveform?
YES
Check the input(Pin148) of Decorder(IC901).
Can you see the normal waveform?
YES
Check the output signal of Decorder(IC901).
Can you see the normal waveform?
Check the input and output of HD2.4(IC401).
Especially you should check
The H,V sync and clock.
Can you see the normal waveform?
YES
After checking the Power of AV switch you
should
decide to replace AV switch or not.
After checking the Power of AV switch you
should
decide to replace AV switch or not.
After checking the Power of Decorder you should
decide to replace Decorder or not.
After checking the Power of Decorder you should
decide to replace Decorder or not.
This board has big problem because Main
chip(HD2.4) have some troubles.
After checking thoroughly all path once again,
You should decide to replace HD2.4 or not.
You should check power lin & IIC lines.
NO
NO
NO
NO
NO
NO
TV/CA
TV doesn’t display
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