Black screen w/sound. Samsung QN75Q7FAMF

[BorisB]

New member and new to troubleshooting LED TV’s.
Issue began with vertical and horizontal lines on the screen after remounting the TV. I cleaned both ends of the connection ribbons attached to the T-CONN board with denatured alcohol on a Q-Tip and reenergized. The result was more vertical lines than before but the picture was clear. After hitting the home button on the remote and arrowing up, the screen went black with the lines still visible.
Sound is on. I can change channels and volume with remote but the home button makes no changes.
I performed a flashlight test and no image was noticeable behind the black screen. Backlighting appears to function properly. I re-cleaned the ribbons using contact cleaner on a Q-tip and noticed a change in the number of vertical lines but no other changes.
Any advise on what the next things to check would be appreciated. I’ve watched some YouTube videos on checking voltages at certain points but I could not identify those points on my model TV.

[brucetv]

Re: Black screen w/sound. Samsung QN75Q7FAMF

If your getting 13V on pins 3,5,7,9 and your backlights are staying on you have a bad main board, one connect, or bad panel. unhook the one connect and see if you have any lines. you should see a clear message to connect the one connect box. unhook one ribbon cable going to panel at a time. See if picture looks clear on one side that is hooked up. If your still seeing lines it may be a defective panel. Take it to a qualified technician for proper diagnostics.