Horizontal lines on my 55LH40-UA LG tv - Samsung HP-T5064 50 in. Plasma HDTV

I hate to give you bad news but this sounds like a panel issue

Check that you are using a "live" tv jack. You might have to use the remote to switch from Ant A to Ant B etc.

The video processor is an issue. Is the picture quality ok otherwise, in which case it can be repaired fairly easily.

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Check and replace the damaged CCFL lamps at the back-light section. Contact any service technician. If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience. http://electronicshelponline.blogspot.com/
Line, faults & possible causes to LCD screen are given with illustrations. You can get an idea about the fault to an extent.

If you wish to get some details; just Google for the site "Elelctro help". Pull up older posts. Surf the site with patience.
Line, faults & possible causes to LCD & Plasma screen are given with illustrations. You can get an idea about the fault to an extent.

Sounds like panel fault. If you wish to get some details; check the site linked here. Viewing it in "Mosaic" or "Magazine" will make surf easy Pull up older posts. Surf the site with patience.
http://electronicshelponline.blogspot.com/
Screen-shots to defective LCD panel are given. See and compare it to that of your TVs'.

If you wish to get some details; visit the site linked here. Pull up older posts.
https://electronicshelponline.blogspot.com/
Line faults & possible causes to LCD & Plasma screen are given with illustrations. You can get an idea about the fault to an extent. Faults to all LCD & Plasma screen are similar, irrespective of its brand and screen size.

There are some semiconductors or capacitors that are leaky. Might need thorough check up inside the TV.

Call LG for warrenty service,the tv Tuner board have problems.Must be replaced to solved this problems.

You need to set your aspect ratio, check your manual.