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iPhone 7 Bootlooping after battery drain - known bad home button

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  • iPhone 7 Bootlooping after battery drain - known bad home button

    I have a iPhone 7 that came in for a screen replacement.
    The phone came in before a few months ago for an other screen replacement. The home button was damage from the the drop when it came in last time. Touch ID still worked but not the home function.

    I've replaced the screen and everything was good, except for the home button as stated.

    Yesterday the phone came back, the screen was broken again, and the touch was not working because of the broken screen. I've set the phone aside until today. Battery was drain so I"ve plugged the phone and now it's been boot looping for about 10 min.

    I know that when the iPhone 7 home button does not work, the iPhone 7 will often take a while to boot. I've seen myself waiting 5 to 10 min before some started, but this time it really starting to be a long while, and I'm starting to get worried.

    My shop is inside of a small town, and I've only seen a limited amount of iPhone 7 compared to the hundreds of iPhone 6/6s so far, and I figured I could turn to the community that might have more experience with this model for any advice before I start trying to get this to boot again.

    Thanks, any feedback from your experiences would be appreciated.

  • #2
    Also, I forgot the mention that I did not attempt to replace the screen yet, nor open the phone. I've only plugged it in so I could test what I could before starting the repair, but it seems stuck in a bootloop as stated.


    • #3
      The home button no click problem is usually caused by the ic on the home button flex that needs reballing, Jessa and others have done a video on this before. I'd check the flex under the microscope too as a boot loop is the sort of thing you get when the phone can't talk to the home button.


      • #4
        Can you get a replacement Home button I know the finger print will not work but will behave has a Home Button . It does in all the models below anyway.

        Maybe a good idea to change the screen with an know good one Rule number one which is now embedded in my mind since I joined the forum.

        But it is is total correct You not have a logic board problem until you do this?? After that if still does not work you check for a software fault.

        Is it not the NAND that controls the boot up

        When I heard NAND first I took it has a logic gate?? so not know why they call it an NAND ??

        Could someone explain why they call it a NAND.

        An NAND gate to me is

        Came across a bus early on in another post and thought it would be a number of lines but it had only one

        I had an issue with a 7 myself where it was boot looping after I tested a new screen on it without the Home Button.

        The 7 has far has I am ware will not boot (will loop) if it does not have a home button installed. So if the Home button is faulty the NAND maybe detects it and says no way you are not allowed to boot
        Last edited by eDigitCom; 01-25-2018, 07:26 PM.


        • crea2k
          crea2k commented
          Editing a comment
          The home button on the iPhone 7 is a non mechanical button, it won't work at all if you swap it for a another button as they are paired to the cpu.

          The screen also won't cause a phone to boot loop, it's possible a damaged front camera flex would though so check this is present and flex is undamaged as missing / damaged front camera is also a iPhone 7 boot loop creator as well as the home button missing or damaged.

          Nand is called nand because the individual flash memory cells exhibit internal characteristics similar to those of the corresponding gates.

        • Mohammed
          Mohammed commented
          Editing a comment
          The flash memory is called NAND because it's architecture is based on NAND gates. This is opposed to NOR flash memory which was used in the iphone 3 IIRC.

      • #5
        So you have to do without a home button features if the original home button does not work on the 7


        • #6
          You have to use assisted touch, the phone pops up a message usually and enables it on screen. The main problem is it takes aaaaaaaages to boot. Iv had some phones that take a good 5 minutes to boot when they have a damaged home button.


          • #7
            crea2k I know that the front camera is good (Unless damage from the last drop), and I know that the home button is damage.

            The phone was turned on when we got it for screen replacement, but the battery died by the time I was going to start the replacement of the screen. I charged the phone to test what I could before starting, but the phone never turned on since. It only bootloops.

            I know that a faulty home button will cause it to bootloop for a long time, but they usually start after 5 min or so.
            I wonder if I replace the home button with a new one, even though it wont work because it wont sync to the phone, if it would at least stop the bootlooping.

            Any thoughts?


            • #8
              I'd try unplugging the home button and then leave it to boot. As iv tried repairing the home button flex before and ended up with just boot looping until I unplugged it and waited.


              • Sly
                Sly commented
                Editing a comment
                Ok, I'll give that a try.

            • #9
              I tried without the home button, and no luck. I've got a bit more information about this phone, and it got dropped and kicked around by kids at school. I'm maybe looking more at a board problem.
              I'll give an update if I get lucky with it.


              • #10
                Look at the iPhone 7 classic faults thread, I had a 7 with audio IC failure that wouldn't boot, just sat on Apple logo and occasionally boot looped every few minutes. Incidentally, I could actually click the home button on the Apple logo screen and it would haptic feedback, so it was almost fully booted but with no working home button you can't confirm the exact same symptoms, however that might be the case.


                • #11
                  I've done some more testing with a known good iPhone 7.
                  Here are some results

                  boot time known good iphone 7
                  18 to 20 sec

                  boot time known good iphone 7, disconnected home button
                  4 minutes

                  Boot time know good iphone 7, disconnected home button & Fcam
                  4 minutes

                  boot time know good iPhone 7, home button connected $ Fcam disconnected
                  18 to 20 sec

                  That is were I'm going to check next.

                  iTune can detect the phone, ans knowns in what state it is in.

                  I've restored the phone, and it knows there an Apple id.
                  I can move ahead with the installation through iTune. The phpne's memory seems intack as it communicates its info to and from the computer.

                  It's like the phone itself is on, but the image on the screen wont pass the apple logo, and eventually reboot.

                  We might be on the trail of a signature symptom. Thank you for your comment.

                  I'll keep you posted
                  Last edited by Sly; 01-29-2018, 01:23 PM.


                  • #12
                    So this phone is detected by iTunes in normal mode?
                    boot looping in iPhone 7 seems to have many causes, none of them leaving any physical signs on the board. I’ve invested in a known good housing to be able to rule out parts issues.
                    what I’ve seen so far causing boot loop:
                    iphone 7 with bad fcam flex —even new ones
                    iphone 7 with bad screen
                    cracked soeaker amp
                    bad joints on any i2c line under audio ic
                    bad tristar
                    bad bbpmic
                    bad bbcpu

                    i can confirm that an iPhone 7 will boot with no audio ic or speaker amp

                    what we need to do as a community is start a knowledge base of dc power supply signature boot sequences. Hopefully we can find some patterns on boot sequence that point to specific issues. For example—when i2c line X is noisy the phone stutters on dcps at point X. When bad fcam is noisy/open it stutters at point Y.

                    one of my priorities is to be able to graph my dcps boot sequence, I know that Mohammed is able to do this and I bought the power z dongle in the hopes of doing the same, if that doesn’t work I’ll buy a new dcps that allows graphing.


                    • #13
                      Thanks Jessa,

                      Yes, the phone is detected as normal in iTune. It knows the name of the owner. I can restore it with no problem, it knows the Apple ID of the owner, yet the phone it self stays on the apple logo.

                      You mentioned that it will boot with no audio ic or speaker amp. Just to confirmed do you mean that it will boot with those IC off the board, or when those IC are defective.
                      Last edited by Sly; 01-29-2018, 03:49 PM.


                      • #14
                        I would like to rule out Fcam in that list as it appears to be an easy one to do, and is being handle with every screen replacement.

                        I've confirmed that with a good iPhone 7, that it will boot with the Fcam disconnected under normal boot time. (More samples from other known good iPhone 7 needed to confirm this),

                        My theory for Fcam:

                        Going from other reports of other people having issues with booting and Fcam.

                        1.I suspect that if the Fcam is damaged, and connected it might cause it to bootloop, but disconnected it should boot.
                        If it does not boot with Fcam disconnected
                        2.I suspect that if the Fcam is damaged, and connected it might cause it to bootloop, the error messages might corrupt the phone and still cause it too boot loop with it disconnected.

                        I would like to hear from anyone who has experience any issues with the Fcam.


                        • #15
                          The power z dongle seems to be a great way of graph dcps boot sequence May try this myself Would like to be keep updated on this if possible

                          Maybe you put out a video tutorial on it in the not to distant future??

                          I seen a video by STS Telecom where he bought a Siglent SPD3303X-E,

                          I think it shows graphs of the power supply input to the phone and displays on the screen also