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iPhone 8 ain't booting

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  • iPhone 8 ain't booting


    Bought a faulty iPhone 8 from my supplier in the hope i can gain some experience in diagnostics and logic board repair.
    But i'm stuck already!

    History
    bought the faulty iPhone 8. Defect not known.

    Visual exam
    - Phone has cracked screen + backcover glass but no bents.
    - Prompt to boot on DCPS gives a nApple Logo on screen but is stuck. (see DCPS current consumption in attachment)
    - Charging (with known good parts) on AMmeter is dropping from 0.42A to 0.08A and is staying there.
    - Logic board looks in good condition and at first it looks like the heat anti dissipation sticker (the black covers over the components) are original and not been removed in the past.
    - Once the black sticker was removed i saw that the hydra + audioamplifier + charging mosfet + wireless charging is covered in under-fill! That reminds me of an Apple Refurbish?
    - Cannot put phone into recovery or DFU. iTunes isn't recognising the phone.
    - Tristar test passes

    Diagnose/work done
    - Removed under-fill around Tigris and charging mosfet and replaced those two IC's.
    - Also replaced Hydra with a brand new one, to be sure.
    - iTunes still don't detect a phone.

    I'm tempted to remove audio amp and wireless charging IC's because they have under-fill and i don't trust them.
    But i don't want to add more variables. Can you tell me if those two are removed should the iPhone 8 atleast fully boot?

    Thanks as always
    Attached Files
    Last edited by GuruFix; 01-30-2020, 10:26 AM.

  • #2
    The DCPS is a little difficult to see because it goes on for so long. In general, if DCPS bounces around and then goes up to 1A in less than a minute then the phone is booting. Yours looks like it does this.
    I don't see you mentioning using known good parts. These phones are extremely particular about charge ports. They do not like many aftermarket charge ports, and bad charge ports can cause all kinds of problems. You also need to split a screen to see if this phone makes image (independently from backlight). Get a known good screen and charge port that you've "proofed" with another iPhone 8 and let us know what this one does.

    Underfill in that area on iPhone 8 isn't "refurb" it means Apple revised the board and some of the manufacturers produced some runs with underfill, other factories did not have underfill there. I wouldn't automatically suspect bad speakers amps or any other chip other than tigris on iPhone 8

    Comment


    • #3
      Tested again to be sure, so all parts that are being used are proofed.
      - Battery
      - Display
      - Charging port

      Charging
      - with known good parts charging port and battery and display connected.
      - starts at 0.42A then drops to 0.08A on AMmeter
      - Phone is giving the apple boot logo and is stuck there.

      DCPS
      - Prompt to boot with power button
      - Phone gives an apple boot logo, so no need to split this known good test screen. I do have image and backlight.
      - Also added a shorter DCPS graphic for more detail.

      Under-fill is good to known fact! Thanks for that.

      DCPS is bouncing up to 1A in less than a minute but it isn't fully booting. iTunes isn't recognising as a iPhone.

      It hurts me that you doubt my putting-in-DFU basic-skills
      No DFU with the following methode.
      1. Quick-press the volume up button.
      2. Quick-press the volume down button.
      3. Press and hold the side button until the screen goes black.
      4. Release the side button once the screen blacks out, then ...
      5. Quickly press and hold both the side and volume down buttons together for 5 seconds.
      6. After 5 seconds, release the side button without letting go of the volume down button.
      7. Continue holding down the volume down button for at least 5 seconds.
      Screen is staying black as it should but iTunes isn't responding with the a message.
      Attached Files
      Last edited by GuruFix; 01-30-2020, 10:28 AM.

      Comment


      • #4
        Ah--you confirmed my suspicions. I'm going to give you an easier way to get a phone into recovery mode. Look for a video on iPad Rehab YouTube channel. I'll come back and put a link here when it's done.
        I think it is reasonable to restore this phone since you've changed tigris/hydra which may have been the original problem, and now you need to clear software corruption.

        Comment


        • #5
          Find the FORCE_DFU pad. Inject 1v8 using red alligator clamp to tweezers, tweezer touch FORCE_DFU, black alligator to board ground (any screw). Connect battery, prompt to boot with 5v USB-----this takes you to INSTANT DFU mode.

          Comment


          • #6
            - Tried to enter DFU your way but no response from iTunes.
            - Removed Hydra to diode mode. Figured if i cannot enter DFU maybe Hydra isn't working.
            - Diode mode gave 0.001 on H5 PP3V0_S2 !! Gotcha. Short circuit!
            - Traced it back to C4216 PP3V0_PROX_ALS_CONN and removed short
            - iPhone is booting!

            Next step is testing the phone
            - There is no loudspeaker sound
            - Recorded video's from rear and front camera don't play. Just stand still like a picture. Cannot press pause/play.

            Keep you posted
            Last edited by GuruFix; 02-01-2020, 01:52 PM.

            Comment


            • Jessa_the_Professa
              Jessa_the_Professa commented
              Editing a comment
              I would diode mode at the dock connector and try a few different docks. A lot of iPhone 8 audio problems that look like audio ic fault in the 7 end up being the 8 dock.
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