i was on the phone and it suddenly shuts off, when i get home i plug it into the computer and the apple logo comes on and off, i put it in dfu mode and restore it and i get error 21. the phone doesnt power up unless its plugged in and when it is plugged in the apple sign just comes on and off. i took it a a phone repair store and they have no clue what to do. i try it some more and i managed to get a error 1204 and -1. i dont know if something is wrong with the hardware and my warranty expired 2 months ago. help please. ive tried everything in my knowledge