I can put it into DFU mode with the battery disconnected, itunes finds the phone in DFU no serial no, but ITunes wont complete restore, error 21.
redsn0w detects the phone in DFU mode, and after using the tool for leaving recovery loop, it says restarting, but then I just see apple logo flash quickly, and this repeats itself every 15 sec.

And it gets warm just around the flash memory area.

Did you solder new connectors on the motherboard for the battery? That can be the issue. Try to use a charged battery and turn on the phone without being plugged in charger see if the apple screen shows up.

I managed to put the phone into pwn DFU, and thereafter it actually completed a restore, it programmed firmware and baseband. All went well, but after completion it flashed apple logo and black screen.

However it actually booted, played a tune and got activated with Itunes which now recognizes it show serialno and pnone number.

Screen is black, but it responds to cable out and in, and in itunes I can see the batery is charged at 63%.

So I guess it is the screen connector afterall, I have tried with another lcd but the same problem.