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iPhone 6 Plus - Boot Looping Dilemma

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  • iPhone 6 Plus - Boot Looping Dilemma

    Hi everyone,

    This is my first post! I'm diving in logic board repair so I am new, so I apologize if my post below is not what's expected. While my goal is to find the main issue, what I really what to accomplish is the thought process & workflow to properly diagnose these issues.


    - I received an iPhone 6 Plus, from a friend, with a cracked screen at the top-right, but they said the phone had been working fine minus a couple of touch issues that day.
    - I noticed the phone was powered off and I did not test to see if it would power on (my mistake).
    - I took the cracked screen off and went to replace it only to find out I was out of stock. So, I replaced the old screen and went to turn on the device... Would not boot. So I hooked it up to the DC supply and the phone booted, but now their were grey vertical lines and you could not make out the Apple logo. I thought I might have missed a connection or debris so I cleaned it up and re-connected multiple times, only to find the same result.
    - I went to a local parts store and picked up a 6+ full assembly screen replacement. I connected the new screen and booted the phone up with DC power... Screen worked great, but the phone rebooted when it reached the home screen.

    - Board is still in the housing, but did review under microscope regarding the top right section of the phone where the screen cables sit. I also checked the battery connector and nothing stands out.
    - Im trying to check software or hardware (power button, charge port, battery) before going deeper in the board.

    - I measured the voltage on the phone's battery -- 2.9v
    - Connected DC power to the phone to see if any current spike for a short -- no increase in current when connected.
    - When booting the phone on DC power (set @ 4v), it boots up normally reaching just above 1amp, but once it's on the Home Screen, the screen went black & current dropped. I clicked the home button to wake it up, then it rebooted.
    - I checked with the USB Ammeter, plugin the device, and it shows 5v, but only goes up to 0.23 amps, then reboots (does not make it to the Home Screen).
    - I then wanted to see what it would do when I plugged it into my computer to see if iTunes would connect. After I plugged it in, it does a really quick reboot, almost like a flash. It shows the apple logo then immediately goes black, show the apple logo again, then goes black.

    - I know the Power Button works, so I have ruled that out.
    - I wanted to check software before hardware, but it's not letting me connect so I can't test that.
    - I am getting 3 different phone reactions depending on if it's hooked up to DC Power, Power Cord (wall socket), Power Cord (computer), so that's very strange to me, but what they all have in common is boot looping.
    - I could test with a new battery, but even with DC power, the phone still reboots, so I doubt the overall issue is a bad battery.
    - I could test with a new charge port, but again, even with DC power the phone wants to reboot, so I dont think that is the main issue. At the same time, ruling out the charge port would point to a board level issue.
    - Lastly, my friend did mention having some touch issues. She mentioned it was hard to scroll sometimes & apps would open themselves without her touching it. Im not sure if this can cause boot looping, but this could have been caused from the cracked screen.

    Before attempting to just change Tristar and/or Tigris, Im curious if there is anything else I should test first or if anyone else has encountered this type of phone reaction. The USB ammeter only reaching 0.23 amps, then cuts off, intrigues me as I feel like that points to an IC issue.

  • #2
    Just saw this post:

    Very similar time my issue. I like the advice and thought process. It looks like I will test with a known good Charge Port to rule out parts problem.


    • #3
      My crystal ball says this is "dog damage"
      iPhones are like cats, they need precision and gentleness. MacBooks are like dogs--you can poke and prod them and give them a rough pat on the head and they don't mind. We see beginner students that sometimes have a tendency to treat iPhones like dogs instead of cats. This is what we call "dog damage" It comes from generalized roughness.

      I'm guessing that is the case here because your disassembly/reassembly damaged the screen flex--this is the cause of lines through the Apple logo that you describe.
      Secondly, I'm guessing that you have dog damage because you have variation in what the phone does based on how you connect it. This is *most* likely parts or connection. If you begin to degrade the plastics of the ports then you will not be able to make reliable connections.

      This is absolutely a parts issue--until you prove that it is not. This means putting the logic board in a KNOWN GOOD, preferably native OEM housing and see if any of these problems persist. If so--then you have a board problem. Only then.

      My advice---make your connections under the microscope for a little while so you can be sure you don't have crushed plastic, bent/twisted pins, long screw damage, small flex tears/creases etc.
      And be super gentle.