What caused my screen to go black?

Originally, our problem was a gray screen with lines but showed the Apple symbol and progress bar, which would go about 2/3 and then go to complete gray screen, then black screen, then restart. We replaced the logic board and then just had a black screen. You could hear the CD powering, but nothing else (no start up chime).

We ended up taking it to an Apple Certified Technician store who told us they “chase the symptoms” and determined it was the display to which they could replace for $300.

I asked them if the logic board was okay since that is the only thing that was replaced and we at least had a screen with the old one. They said they didn’t have a way to test it, but could put the computer through a stress test.

Long story short, they said that the wrong thermal paste was used on the heat sink. When I picked it up ($165 later) it was working. I brought it home and started a Time Capsule backup, which was going to take hours, so I left the cover open all night. It went into sleep mode. I started playing around with it the next morning (checking emails, etc.). The backup was still in process when I clicked on “Enter Time Capsule.” As soon as I clicked on that, the screen went to all green tiling.

I immediately pressed the Cmd-Opt-R-P and it repeatedly cycled through the startup chime with the green tiling. I powered down and back up and got the same thing as after the logic board replacement - black screen with only the CD powering. I say that, but since I could not see anything, I really do not know.

That is the only thing I could hear. :) What could be the issue now? Could it be the LVDS cable (part GS17616)? I assume LVDS has something to do with the video. I do not believe it is the display as we had a picture before it went black. Any advise will be appreciated.