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iPhone 7 No Charging Issue

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  • iPhone 7 No Charging Issue

    I just subscribed after finding this forum, and I wanted to say that I really appreciate Jessa and the creators of this forum. I subscribed because I am banging my head against a problem, and I need some guidance.

    I bought a box of scrap phones from another iPhone repair shop in town, and have been going through them to see if any of them are worth saving. This will give me the opportunity to learn without damaging someones iPhone during my practice.

    I am currently working on an iPhone 7. This iPhone will work fine on my power supply using an iPower Pro. It will also work fine with a charged battery installed. The phone will charge a battery, if the battery has enough juice to start the phone.

    The problem comes when the battery is left to die, or is removed completely. If I just plug in a new charger port, and no battery, the phone will not give me an Apple logo when plugged in, and pulls 0.00 amps from my charger.

    I am unsure about the devices history, but the metal plates have been removed from the back of the logic board, over the tristar chip. The area was cleaned of any flux, and looked to be in good condition. I did notice a chip in the Q2101 chip. I was not sure if that was the cause of the problem, so I replaced it.


    That did not solve my issue though, so I moved on. I started testing the Tristar and Tigris chips to see if they were getting the power they need, and if they were outputting the power they should. This took me a while, because I was testing with the iPower Pro, so the logic board was getting power from the battery connector. I realized my mistake, and plugged in a new charger port. The readings I took can be found in the photo below.


    I had periods when I thought I was on the right track and replaced the Tigris IC. I thought it was Tigris because the iPhone would connect to my computer and I was able to restore it with iTunes, so I thought it was unlikely to be Tristar.

    After replacing Tigris, and Q2101, I would hate to just go willy nilly replacing tristar, if I wasn't on the right track.

    I hate not having a good history of the device, but I am hopeful because under battery power it does start up.

    If anyone here could just put me on the right path, I would really appreciate it.

  • #2
    I went and took diode mode readings from the battery connector and the charger port connector. I found some out of spec pins, that I will be going and looking at. I am posting the readings as attachments.

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    • #3
      I went back and took a look with the microscope, and noticed solder balls around the charger port connector. It looks like they maybe tried reheating Trinity. I am going to clean this area up, and see what sense I can make of it.

      I am stupid, I didn't even look at this area when I took a look at the board initially. I was too focused on the damage to Q2101, andf the Tigris chip, to look into it further.

      I am going to clean up this underfill, and see if I can remove the shorts, and then re-assess the situation.

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      • #4
        I am leaving this here for any future reference, or people that might have a similar issue. Both of the shorted pins on the charger port connector end up in this section, so that is where I will move on to, after I get the underfill cleaned up around the connector to make sure I don't have any bridged caps there.

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        • #5
          I cleaned off the underfill, and removed the leaked solderball. I did not see any bridged caps, so I am moving on to the back side of the logic board. The caps on the front side, appeared in good condition, so I am hesitant to remove them without cause. I will see what the back looks like, and go from there. Right now I am pretty inclined to remove the Tristar chip, and see if that removes the shorted circuit.

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          • #6
            I removed Tristar, and reballed and replaced it. That cleared up the shorts, so all the readings from the charger port connector are in specs, as far as I can tell. The logic board still shows no signs of life when plugged into only the charger port, without a battery. No Apple logo, 0.00 amps from my USB meter.

            I am about to head home. I will work on this some more tomorrow.

            Comment


            • #7
              "The phone will charge a battery, if the battery has enough juice to start the phone."

              That is a well known tristar symptom. Tristar is mostly a data chip, it's outputs are ones and zeros that have no meaning to mortals. It is the most commonly damaged chip across all phones. You have balls squeezed out of trinity meaning that someone has already tried replacing tristar---and it didn't go well for them.

              The very first thing to do on this phone would be to replace tristar, that's a no brainer. The only way to rule out tristar is to replace tristar.

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              • #8
                Originally posted by Jessa_the_Professa View Post
                "The phone will charge a battery, if the battery has enough juice to start the phone."

                That is a well known tristar symptom. Tristar is mostly a data chip, it's outputs are ones and zeros that have no meaning to mortals. It is the most commonly damaged chip across all phones. You have balls squeezed out of trinity meaning that someone has already tried replacing tristar---and it didn't go well for them.

                The very first thing to do on this phone would be to replace tristar, that's a no brainer. The only way to rule out tristar is to replace tristar.
                Thank you Jessa, for responding to my question. I was just eating dinner, when I resigned myself to replacing tristar. I removed and reballed it, but it must have failed entirely. I will try that tomorrow, and let you know how it goes.

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                • #9
                  Never ever ever reball a tristar. It does not fail
                  from drip damage—it fails from electrical damage.

                  Changing tristar is an oil change. Don’t put someone else’s used motor oil in your car when you are doing an oil change.

                  This job job was a classic tristar fault from minute one. A no brainer. It seems like you are spending an awful lot of time trying to make the problem be the problem you want to solve ...but the problem is what the problem is.

                  Change tristar.

                  Comment


                  • #10
                    Originally posted by Jessa_the_Professa View Post
                    Never ever ever reball a tristar. It does not fail
                    from drip damage—it fails from electrical damage.

                    Changing tristar is an oil change. Don’t put someone else’s used motor oil in your car when you are doing an oil change.

                    This job job was a classic tristar fault from minute one. A no brainer. It seems like you are spending an awful lot of time trying to make the problem be the problem you want to solve ...but the problem is what the problem is.

                    Change tristar.
                    Gotcha, I will do it.

                    Comment


                    • #11
                      I just wanted to say thank you for the help. I replaced Tristar with a new one, and the phone is working now. After reading through some posts in the knowledgebase section, I think I have a better understanding about what to look for in regards to Tristar failures.

                      I am going to put this sucker back together, and put it in my done pile.

                      Thank you for the help.
                      SquidBilly
                      Friendly Contributor
                      Last edited by SquidBilly; 08-22-2018, 03:27 PM.

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