Iphone 5 unknown device

[mb83]

I have iphone 5. It was dead. I've changed U2 and everything is working now exept usb. When i try to connect to computer it shows me "unknown device". I tride another computer, original cable, i even change U2 and nothing working. Please help

[GPU5970]

U2 responsible for usb and uart. In some cases , when it burn, voltage +5v can go to CPU usb data lines and cause breakdown of these lines. Also, u2 is very close to CPU and when you replace it there is a possibility of overheating and solderings balls under processor. CPU is very hard to reball, so do special analysis before reball. Try remove U2 and measure resistance between GND and contact pad that go to usb data lines. It should be equal and not in short circuit between d+ d- data lines. Also you can apply a 2v on laboratory power supply with stabilized amperage 100mA to contact pad of data lines. CPU should not consume a lot of current or be heated.

[mb83]

Thanks for reply… This problem was before i've changed u2 so i think this is CPU problem… i'm shore that i do not overheat cpu. There is no other posibilites? some capacitor, jumper etc? If this really cpu this phone is trash

[GPU5970]

So that's another thing if it was the initial problem.
1 Check or replace dock
2 Check 5v on C304 capasitor with usb inserted
if not ok- replace Q2 (usb 5v protector) and check or replace r111(5v fuse)
3 Check l20 l22 fl60 fl53
4 Check L1 L8(data lines inductors between U2 and CPU)
If all ok, it can be CPU- how to check CPU in first post.

[ATF05]

I also did not work////////

[mb83]

I've checked eveything, i replace u2 one more time but still problem exist...

[dog68]

With iphone 5, you have to be careful with tempreture, even when soldering on a coil, an underboard pre-heater is a good tool to have for these.

[mb83]

I replaced a lot of u2 and this is my first case with this kind of problem. Unfortunelly any solution in this topis was not worked. So i think this is cpu. Client wont be happy but what to do thanks for replies !