DIY repaired iPhone won't boot fully - flashes Apple logo when powered via USB I recently tried to do a screen repair on an iPhone 4. 

It won't boot fully, so I may have managed to break something else. Basically it wont turn on, and I only get a flashing Apple logo when plugged into a computer. I believe it could be the motherboard, although I have visually inspected it extensively to determine if i could have physically broken anything. I could not detect any fault. When I use the suspect motherboard on another iPhone frame I get the same problem.
Get into DFU mode and do a restore in iTunes.

For DFU mode:


Turn the iPhone off (not needed in this case :)
Push the sleep button for 3 seconds (Apple logo should appear)
Push both buttons for 10 seconds (Apple logo should disappear)
Release the sleep/wake button and hold the home button for at least 15 seconds.


Nothing will show up on the screen, but if you connect it to iTunes it should recognise it. Then do a full restore.

If that doesn't work, you screwed something up inside, you might want to open it up again and re-check all connections.