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Post originale di: Juan Pablo ,

Titolo:

iPhone4s dead drawing 300milliamps on power on

Testo:

Hi friends need some help here, no one seems to help me in the right direcion. I got an iphone4s board to practice doing measurements. I removed all the shields entirely with high air flow and temp around 400. Before this phone was working.

When I came to inspect under the microscope I saw some solder balls in the area of the PMIC and most likely could be near the nand as well. Nothing visible on CPU side.

So now I checked all different rails there are no short on main VCC. I used a thermal camera and as soon as I trigger pmic starts showing a visible footprint on heat.

I checked resistance measurements around all lines from pmic main important ones 1.2SDRAM , CPU , NAND and there are no shorts at all. I even measured secondary LDO’s from pmic and they’re ok, the only one which showed low resistance on both sides was PP3v0_optical , but again I removed the cap on this line and still when powering on the device I get 300Milliamps.

I asked to some other friends and they say just remove TOP RAM from cpu “they say is shorted” even me telling I did all measurements on volage feeding it without having shorts.  So if the lines feeding the CPU RAM are not shorted could it as well be bad by some internal resistance?.

Now I’m lost.. need some other ideas.. how to keep on taking measurements.

Thanks

Dispositivo:

iPhone 4S

Stato:

open