LG 55LH40 is showing only the top quarter of the picture. The rest of the image is blank. It functions this way on all inputs.
Large TV screens are made up of 3 or more sections, and each has a separate driver board controlling it, both on the circuits inside, and in the actual TV thin film screen panel (that's the clear panel that actually has the picture appear on it, then a back light shows it up).
To know which part has gone faulty is very difficult to diagnose without the right electronic testing equipment and training in tracking electronic faults down. But you can narrow it down quickly as there are only a few simple parts inside a TV.
If possible, you need to track down either the correct driver board and try replacing that, or unfortunately it can be the actual screen itself has gone faulty (this is rare but does happen).
As an example, I had a 32 inch TV, perfect working order back in 2007. My house electric got a power spike and the electric all went off. When it came back on, the TV only had one 3rd working (top 3rd). I had to change the whole TV front panel - all of the other parts were still perfect. To learn about TV repairs I took the display apart to track the fault piece by piece - I was told it wasn't possible by 3 engineers in shops, but it can happen, the actual flat panel was at fault, and a replacement at a yard sale for $15 fixed it again. That was a few years back and ive fixed about 30 since then, i'd say a quarter of them just needed the whole display changing (not the actual back light section or T - CON board if it's that type)
It's also possible that there is corrosion / oxidation on the screen contacts, and its easier / cheaper to try cleaning them first with appropriate electrical contact cleaner.
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