What you described can be a symptom of a bad T-Con Board or Logic Board, bad capacitors on the logic board or even a bad connection on one of the ribbon cables. Try the following.
Unplug TV and remove the back cover, unplug and reattach all Ribbon Cables, while you have it open look for bulging capacitors on the Main Board "board with Inputs"and the power board.
This are both common issues with some models of LED TV's, bad connections and Faulty Capacitors. LG and Samsung are bad about using crappy capacitors in Low to Medium range TV's.
If you see no obviously bad capacitors and you reattached all the ribbon cables then partially reassemble and test the TV, any change?
- No change then from this point you could have either a bad T-Con board of bad "Logic/Main/Input board" name varies depending on manufacturer but it is the same thing. Some models have the T-Con board built directly into the display and can not be replaced which means you would have to attempt to replace the Main board and hope that solves the issue, screen replacement is rarely worth the effort as screens are 1/2 to 3/4 the cost of the TV new. From this point I would need the Model number to troubleshoot further.
Here is a decent place to start with DIY TV troubleshooting.
https
/www.youtube.com/channel/UCGfTWLdZHHmhtb-qUb5vb2Q
Which is http
/www.shopjimmy.com/
Any questions feel free to ask I repair General Electronics as a Hobby which is everything from Computers, TV's, Tablets, Cell Phones, Laptops and Driverboards for Local machine shops, Car PCM's and Transponder Key programming for small local dealerships.
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