phone does not start properly after replacing rear panel and battery
I followed the 3GS replace rear panel / replace battery guide.
Once complete I tried to start, nothing happened.
I connected to laptop via usb. Phone screen is illuminated and apple logo appears for approximately 4 seconds, the switch off, and the same over again.
I assume without being aware I made a mistake in re-assembly, or even broke something during the action.
Does someone can advise what component / cable / connector might be affected?
Obviously the screen works, and something electrical works.