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Iphone 7 hangs at boot but not audio or baseband (i think??)

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  • Iphone 7 hangs at boot but not audio or baseband (i think??)



    Has anyone ever seen an iphone 7 boot hang like this? Get error 4013 if I try a DFU restore. The picture below is not in DFU mode, its just hanging at .25
    Dissconnected everything removed the board from the housing and and used different screen. Same behavor. This is a new one I've not seen in the 40+ iphone 7s i've worked on. Phone is in fantastic condition no signs anywhere. There is a slight crease in the sticker between the sim card and CPU shield which is my only clue it *might* be flex damage but this is not a typical hang from that damage i've seen. Just looking for ideas before i do the usual. It is an A1660 qualcom board. No shorts around baseband.
    Attached Files

  • #2
    So the very next A1660 I have on my desk I open up and stick it on power Z kick it out of DFU mode and it has an almost identical problem! It also is in perfect shape with a slight crease mark in the same area. Should I go after audio ic or baseband PMU first?
    Attached Files

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    • #3
      I would rule out tristar first since that is definitely not a match to audio or baseband as far as we know

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      • #4
        Hmm i was able to connect and start the restore via iTunes, though it failed. That doesn’t indicate a good tristar?

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        • #5
          Well I swapped out tristar. Same issue. Not knowing where to go next really and staring at this crease in the sicker between sim and cpu shield, I made the call to just try the audio ic. 4 jumpers and a new audio ic later, same issue. I decided to reflow the Qualcomm baseband PMU since the board was already hot from the nearby audio ic cause I’ve seen these Qualcomms break connections at the balls. Of course no change. I did get an invalid serial on one of the restores. So I popped off the nand (after confirming 3V and 1.8V nand voltages are there) and it read just fine. I still put a new one on with fresh programming from old chip. I think the invalid serial was from my test housing going bad.

          Really need to figure this one out as I have two on my desk with same symptoms. Surely someone has seen this? I’ll post a pic of what it looks like when it freezes on restore. iTunes log didn’t give any hints like always
          Attached Files

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          • #6
            If you're using 3utools the invalid serial number is just a bug with it. If you use iTunes it'll work fine. As iv had iPads before give that error and they work fine in iTunes.

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            • #7
              It doesn't match a known signature problem---yet. So yes, definitely try to figure it out. Hanging at 250mA seems high so I would look for short. The only other signature no boot problem that iPhone 7 gets is short within SDRAM, but that usually causes a very characteristic heat at SDRAM in a perfect square, and DCPS either goes very high, or....after the CPU is killed, just a flash flash flashing of current. Some folks think the SDRAM shorts can also then affect pmic, so you might want to check your sdram voltages and other pmic outputs.

              Check other things that can fail in an unopened phone---image power and backlight and speaker amp.

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