I'll tell you my screen replacement saga. I had three broken N7's here (two were mine, and one my son's girlfriend's young daughter). I ordered a replacement screen/digitizer and tried replacing her screen. First, getting the screen off was tricky, but I got it off, and put the new one on. Got everything hooked back up and no power. Ugh. I sent that screen back and they replaced it. Then I tried again. This time, hers had power, but half the screen was green and the other black. I took apart one of the other ones that I had, and compared motherboards. I could see obvious damage to hers, so tried putting that screen on mine. On that one, the OTHER half the screen was green, and half was black. I tried swapping the power ribbon on them to see if that made a difference. They behaved differently, but still had garbled screens.
By this time, I wasn't sure what was going on, but hey! I had a third one that I could try! So I tried the screen on that one and lo and behold it worked perfectly. My guess (and I'm no techie) is that sometimes when the tablet is dropped and the screen breaks, is that something can short out in the motherboard. N7 #1 was stepped on by another child and N7 #2 was dropped by my grandson onto a porcelain tile floor, so both I think had some serious internal damage. N7 #3 was dropped on carpet, and didn't sustain a hard fall (I was shocked it broke, honestly).
Good luck, and hope you get it to work. I think I'd try a different screen and see if that makes a difference first.
Facebook
Twitter
Instagram