Ok, thanks -- Got it.
Your problem is a BUFFER BOARD with a bad buffer on it.
Since it's on the SUNG side of SAM SUNG it's going to be the right or center buffer, depending on whether the TV uses 2 or 3 buffers.
E BUFFER -- Part number BN96-12954A
Available here --
Here is how you remove and replace the part. You will have SEVERAL RIBBON connectors on the board you have to remove, and they all have to align squarely into their sockets or you end up with a black band similar to the colored band you see on your TV screen now.
I'm warning you about this because they are in a tight place, and require some patience and good manual dexterity to install them.
You'll have to flip up the locks on the Ribbon cables, lift them up and out because there are plastic tabs on the end of the ribbon cables that lay in front of tabs on the sockets. This assists you in getting them aligned correctly.
I usually take a super thin flatblade screwdriver and use that to unlock the locks, slide the screwdriver under the ribbon cables to lift them up and get them out.
To put them back in, I hold the sides of the ribbon cable and insert them at a 30 to 45 degree angle, then lay them down past the tabs, then lock them.
Make absolutely sure they don't LOOK cocked before locking them !
If you take your time, use bright lighting and observe your work, you should do ok.
I recommend upon completion of the ribbon cables, you reassemble it enough and connect ALL connectors.....then plug it in, and turn it on and look for any black bands before putting it all back together.
I recommend laying the TV face down on a blanketed table to service it, then just slide the bottom of the TV screen off the table so you can see a couple inches by the SAMSUNG nameplate. Just get down underneath the TV while it's on the table and check the lower 2-4 inches of picture for any bands.
IF you see bands....it will be DIRECTLY aligned with the ribbon cable on the Buffer board up top. Realign that specific one above it.
Yes, it's challenging....but certainly cheaper than replacing the entire panel.
If you have any questions, just ask
Tips are greatly appreciated !