This one is stumping me and Google doesn't seem to show anyone with a similar issue. The set powers up fine, has sound, responds to the various inputs and the remote control...but the picture is basically a black raster with various gradually morphing horizontal lines. They're more visible and brighter when a signal is being received, and go mostly darker and greenish when the signal is removed. After I cleaned it out and powered it up for the first time, I was able to see the full, good picture for fractions of a second at a time as flickers, once every couple seconds, in fits, but I haven't seen this for some time now. I've replaced the logic/control board and cleaned all ribbon cables to no avail. My gut says buffer problems, and the (however fleeting) glimpses of a full picture tell me the panel itself is okay, and that it's an image processing fault somewhere. Should I suspect the mainboard? Buffer issues usually present as horizontal lines across an otherwise normal picture, and vertical lines (which I don't have) are usually panel issues. But, I've never seen an all-black screen with horizontal lines. I went through a lot to get this set, so am hoping it can be restored to its former glory!
(Tried twice to use the site's image embed tool but the image just didn't show up at all)
https://imgur.com/a/EfN4TXw