Center of screen has horizontal flashing white lines all through it. Just in the center of the entire screen

Most likely the main board...try locating one on Ebay, then go to you tube for a "how to replace" video.

If you wish to get some details; visit the site linked here. Pull up older posts.
http://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.
Search the site by type in the "BRAND NAME" of your device; (Exclude the model number), in the "Search box at the top right of the display window of the Homepage" to get gathered related posts

Hi,
Probably the T con board is faulty. Tcon board is the one which drive the lcd pixels.
Check the video. LCD TV Repair Tutorial Con Board Common Symptoms Solutions How to Replace...
www.electro-medical.blogspot.com

Unplug it,then wait 10 minutes,then plug it back in.

It's not unusual for a monitor to use different circuit paths based on the the display resolution chosen and so, one could have a resolution that is faulty, while another works just fine. Monitors normally just get dim, or power supplies fail, or other more common failures, blank or white dots... etc.; but, should a monitor live long enough without failing in those areas, usually one or more resolutions will fail. Doesn't leave you much of an option, other than a repair shop, if one could be found; but, as long as it works at that or another resolution, and I'd check the other settings and use it if you have something where it can be used. Sorry for the not so good news.

55hdm71 plasma hitachi vertical lins 3 red on right side what do i do?

The single horizontal line is a problem with the vertical circuit. Look for a small flat id attached to a heatsink that should be marked LA7837 or something similar. Try resoldering the pins of this IC first. If that does not resolve it, replace the IC.

Keep us posted.

Dan

I have seen this on mine. Check the cable going into your TV and make sure it is good. The ground portion of the cable could not be making a good connection.

Picture is reduced to a straight horizontal line across the center of the screen.

sounds like bad capacitors on the FMT board need replacing that is a common fault with the first generation DLPs There are 3 bad capacitors.