Watch videos from https://www.google.com/search?q=shopjimmy+troubleshooting+a+black+screen+lcd+tv&ie=utf-8&oe=utf-8
I know folk don't know this so let's be clear that no TV techs appear on most forums as folk get upset if the guess is wrong. Also there is some question about liability.
The LG led tv screen does not operate a black screen but the LG logo lights up

Informations:-
LG47GA6400 GOOGLE TV
MFG-2013

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GameFAQs
GameSpot
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TechRepublic