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iPhone 12 Pro SHORT on No BOOT

Hi!

I have an iPhone 12 Pro which does not boot up. I have checked VDD_MAIN I had short which I have cleared.

Connected to DC Power and started boot. On the DC Power I can see 31Amp then straight jumps back to 0 than 51Amp than jump back straight to 0 than 165Amp then straight jumps back to 0.

I have put it under Thermal cam And I can see that part of the PMU flashing indicate heat.

I have checked the PMU power lines and found out that PP0V6_VDDQ6L_S1 is SHORTED (Diod Mode 0.000)

After this I have removed all caps on that line but all where fine no broken caps and without them short still there.

After that I removed PMU to check if its bad or not. Short on that line is till present.

Could be the CPU??

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On board wiev there is a resistance level but I could not remember the exact number.

And yes the pmu is flashing around that ball where the line is. Looks like trying to boot pmu area get hot switching off and repeat continously under heat cam

[image|2609033]

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@peterhupuczi Posted an update to my answer, Where was your VDD_Main short? Have you separated these boards/did you separate them before clearing the VDD_Main short?

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On a 0V6 line I would be questioning that it is actually short. A 0.6V line has inherently low resistance to ground and so diode mode would also be very low (although 0.000 is as low as it gets). In theory this could be CPU, assuming it is actually short. I don’t have a boardview handy so no point of reference for locations of this line on the CPU, but I am still inclined to think your issue is elsewhere.

Could you tell where on the PMU specifically was getting hot? Was it in the same general area as the ball for this line?

UPDATE: Yes, There are quite a few spots where this is near Ground under the CPU, And it does show a non 0 diode mode reading when I checked ZXW now that I’m home. I would check if I had a 12 Pro on the shelf, but I don’t. If no other components are getting hot, seems like it’s a strong possibility. Only other spot that it could be, if you removed all the caps, is a resistor that is inadvertently bridged to a nearby ground since that’s all that’s left on that line . But without heat or liquid damage that seems pretty unlikely.

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I also checked resistor on that line and they are all fine and showing normal did readings. I think it is going to be CPU SHORT. Ill remove and recall CPU Today Post an update when I receive my BGA reball plate so I can put CPU back.

Thank you for your time and Input sofar. :)

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Just removed CPU and fault cleared. NO MORE SHORT!!! YAAAYYY

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@peterhupuczi Nice work! Hope reassembly goes according to plan!

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