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iPhone 6S death out of the blue

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  • iPhone 6S death out of the blue

    Customer is telling us he went to sleep with a working iPhone connected with the original charger and he woke up and the phone was death!

    History
    We sold him this iPhone and we have refurbished this model. So we do know it had a broken display and used a back cover before we got it.

    Exam
    Phone is in good condition. No physical damage can be found. Logicboard is completely original and no prior repairs are done.

    - Charging with known good parts gives 0.47A but no reaction from phone.
    - Connected logic board with the DCPS and a known good display. Before prompt to boot 0.0A and when prompt to boot it only gives 0.03A steady. See attachment.
    - iTunes don't recognise the phone. iPhone cannot enter DFU or recovery mode.

    This low of current being drawn, looks like a CPU failure? Maybe flexion damage in the past? Phone was working just fine for over 1 month.
    Where to look next?

    Thanks!
    Attached Files

  • #2
    what is the voltage on cpu reset line--maybe tristar is pulling that line down.

    Comment


    • #3
      PMU_TO_SYSTEM_COLD_RESET_L TP06 = 0.416 diode and 1.74V

      I2C probe points
      PP0900 I2C0_AP_SCL 1.8V
      PP0901 I2C0_AP_SDA 1.8V
      PP0902 I2C1_AP_SCL 1.8V
      PP0903 I2C1_AP_SDA 1.8V
      PP0904 I2C2_AP_SCL 1.8V
      PP0905 I2C2_AP_SDA 1.8V

      POWER STATE CONTROL PROBE POINTS
      PP1021 PMU_TO_OWL_ACTIVE_READY 1.8V
      PP1023 Under sim tray. Not measured.

      AP_TO_LCM_RESET 0.450 diode mode

      Or do you mean? TRISTAR_TO_PMU_HOST_RESET? How can i test this line without removing Tristar?
      Tristar tester is passing fyi
      Last edited by GuruFix; 01-24-2020, 11:04 AM.

      Comment


      • Jessa_the_Professa
        Jessa_the_Professa commented
        Editing a comment
        The reset line under chestnut that also goes to CPU. Check that line for voltage--you may have to remove chestnut or tristar check in 6s. If it is low, then the likely case is tristar, so pulling tristar to check may solve.

        Also, 30mA is low and unusual. Let's make sure we are on the same page. Try DCPS again but remove the usb connection---still 30mA, or is it 70-100mA?
        If it is 70-100mA that is more classic for a phone autobooting to DFU. Troubleshoot why it doesn't make usb connection.

        How did it come to be this way?
        Reset isn't just going to fail on a nightstand.
        This is either charger damage tristar/tigris or an automatic update killed the phone.
        Either way--it should be able to go to DFU.

        You've have two phones with the complaint "can't under dfu" That is unusual--most phones can go to dfu no matter what. Let's understand more about HOW you are attempting to put these phones in recovery mode.

    • #4
      To be sure i connected to DCPS again and used a power button to boot. This way the USB cannot draw any power/current.
      Still 0.02A - 0.03A prompt to boot and this is extremely low. Still not able to put in DFU mode always with known good parts (done it 1000 times)

      - Replaced tristar
      - Phone is booting as normal! This one is fixed

      There where some rare symptions for a tristar defect! Thanks as always
      Last edited by GuruFix; 01-29-2020, 03:36 PM.

      Comment


      • #5
        Yes--look at the schematic. Notice the data lines there are tristar. You can see that damage to tristar on the reset line or the I2C lines can absolutely just kill a phone on a nightstand. This is part of why the customer education piece on unprotected cables is so important.

        Comment

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