I hope that someone can help me with my half dead Nexus 7.
These things have happened to the device:
The previouos owner dropped it, the screen cracked, but apart from that, it was still functional.
They replaced the LCD touchscreen unit with a new one. The device haven't functioned since (not even with the original, cracked display).
I received the device in this condition, and the first thing I noticed, was that the battery was dead (~2,5V cell voltage). I recharged the cell directly (with my own separate Li-polymer charger), and I soldered the battery protection circuit back (now it's completely charged, around 4.16V).
At first I thought that the device had drained the battery while they were waiting for the new display, and the dead battery was the reason why it didn't work for them after the screen swap, but unfortunately it was not the case.
Here are the symptoms:
After reconnecting the battery to the main board, and pressing the power button, I can feel the processor getting slightly warm, but the display stays black (the backlight is off and nothing changes on the display, not even in bright light).
When I connect it to my PC, XP recognises it as a mobile device, and the 16GB flash storage is completely accesible (in the properties menu, it says the device is using battery power).
When I try the 30 second power + volulme up key combination before connecting, my PC tries to install a new driver, without any success.
All this points to a screen problem, but the screen is brand new, all ribbon cables seem to be intact. I wanted to do a factory reset, but all the methods I've read about required the USB debugging mode to be activated (obviously I can't do that).
Interestingly, one time the device started making some sort of a key-press sound (2-3 times) when I pressed the power + volume up buttons, so it is not completely brain-dead.
I've tried the power cable + 20 second powerkey-press method, it didn't work.
Any help is appreciated.