iPhone 6s wont turn on

WeLoveApple

New member
No liquid damage or anything unusual.
It was sucking around 0.2A. Changed U2. After that 0.6-0.7A. Still wont turn on.
Measured important power rails that go in and out of PMIC. Most of them are okay, except:
PPCPU is 0.5v instead of 1v
PP_GPU_SRAM is only 0.15V
PPGPU is missing. I did measure short to ground in diode mode and it is very low 0.015.

So what should I do? My idea was to get off the caps one by one in PPGPU rail and see when is the short gone....
Any better advice?
 

dukefawks

Administrator
Inject voltage on GPU bus and see what heats up. No idea what voltage needs to be there but do not exceed that of course. Start low and monitor the current.
 

jessa

New member
The expected voltage on GPU power here is 0V. Injecting voltage on this rail is a great way to kill a phone permanently. There is no rail more sensitive to injected voltage on the iPhone board than this one.
 

WeLoveApple

New member
In the meantime I found the problem. I started changing the caps on the PPGPU rail and after a while it started working again. :)
 

jessa

New member
Or in other words, you reflowed your fucked up tristar placement so that it was actually seated on the i2c pads and the phone worked. You never had a problem on PP_GPU and it is a horrible idea to spend time troubleshooting this line
 
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