Iphone 4, logo 1 sec then off
 

Hello all

I was testing a new screen for my iPhone 4, and after reinserting the battery the screen flashed with Apple logo for 1 sec and then the phone turned off. It is dead untill I remove battery and then it does the same.

Without battery and into the computer port, the screen does the same.

I put the motherboard into another iPhone, but the problem is the same, so I guess the problem is with the board/software.

I can put the phone into DFU mode and iTunes finds it but without serial and screen only show a logo shortly and then turns off. When trying to restore I get an error 21.

Please help.

change your battery and try

I tried both with and without battery inserted, still the same result. The battery works just fine in my other iphone, I just tested.

I was searching to help you solve your problem is that error21 is a hardware problem due for a non well fixing connectores or a dust that need to be cleaned and from a bad assembly
I think you need to dissamble your phone again and try to assembled correctly that what's appeared with me by searching to solve your problem
Please try and post result

I already put the entire mainboard into another Iphone, and it acted excactly the same in that case... it could of course be a connection gone bad.

Many problems caused for error 21 please read from this linkhttps://www.ifixit.com/Answers/View/...tting+Error+21

it's battery connector missing tracks. check and make jumpers.
for battery connector ways ip4 search google.

I have checked all connectors in this post:
http://gsmresolutionworld.********.d...s-problem.html

All has perfectly fine connections and no shorts.

change your battery.. (battery replacement)

When an iPhone turns on for a second and turns back off, it means it's not detecting the battery. Try to replace your battery. It can be from a damaged battery cable. If that doesn't work, then battery connector needs to be replaced and soldered. Last and least common, IC needs replacement..
Hope i helped.

Thanks for the suggestion, I have tried with two different batteries. No go. Wouldn't the phone turn on when no battery is inserted but connected to power?

When measuring on the red points what should my multimeter be set to measure? Resistance? What is buzzer mode on the drawing?

If the iPhone is functioning normally, it should turn on the apple screen then off without a battery and connected to pc or charger.

Without the battery and connected to a charger the same thing happens with the fast <1 sec Apple logo flash.

Does it keep restarting? or just flashes once?