I managed to repair a Nexus 7 with cracked digitizer. I used it with an USB or a bluetooth mouse, until I recived the new digitizer, so I was sure that all other things was working correctly.
I separated digitizer from screen with a heat gun, and a thin guitar cord tight on an arc (in place of the blade of a metal saw - I have a picture of this setup). Than I removed all the glue from the LCD, cleaning it with a little bit of alcohol.
I tried to mount all without fixing the digitizer to the LCD at all, just to ensure that all was working. Unfortunatly there was a black hole in the display near top left corner, about 1 cm of diameter). I have no idea about wat it was due to, but I am sure it was not due to the alcohol I used to clean the display, since it was there before.
The digitizer was not working very well, sometime it did not sense the touch, or it sensed it discontinuosly, so it was basically impossible to draw a continuos line. Probably because LCD and digitizer was not fixed togather, I thought.
Undecided on how to proceed (by a complete screen with digitizer, or by a new screen to stick to the actual digitizer), I tried to stick the digititizer with just 4 small spot of glue, at the 4 corners.
Now I am using the tablet in this way. The digitizer is usable, once you learn the right sensitivity, and the black hole has gradually disappeared, so the LCD is completly ok. The only defect is one row of the digitizer which is completely unsensitive (a couple of cm from the top edge): if I draw a vertical line, it result interrupted, and if I try to follow that line, the sensed point appear sometimes in the line above, and sometimes in the one below. The result is the a button positioned in that line is very very difficolt to be pressed!
I really have no idea what it can be due to, but it is a very reproducable effect (it happen always - I have never managed to see that point touhed, at any position in that line). Basically the unanswered question is if LCD and digitizer interact in any way, and how.
Now I would like to well stick screen and digitizer, hoping it results in improved touchscreen usability, but I do not know which glue to use. And first of all it would be great if I could discover why that row is not working, and maybe how to make it working. But I am a bit afraid about loosing what I currently have, that is a usable device, even if not exactly as a new one.
Any suggestion is welcome.