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bad case of wtf is going on, on a 6plus

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  • bad case of wtf is going on, on a 6plus

    hi, i have a 6plus that is a nightmare. came in with a dead tristar, replaced it and it worked fine for 5 mins and then c1407 on PMID_cap shorted. replaced both of them from a donor and tigris with a new one just to be sure.

    the phone worked for a day and then died again. tristar and q1403 died. i sold the guy an original lightning cable and an original charger because dude your stuff is frying your phone. i also replaced the battery.

    worked for 2 days and now is dead again with something completely unrelated, stuck on dfu, board getting hot, pp3v3_nand was shorted, error -2, luckily it was only c0610 shorted. i though "this is water damage cancer. it is killing caps" but i could not find signs of it and nobody desoldered the shields before. tristar was still overfilled the first time i opened it up. oh and it refuses to charge the battery. power z draws 0.008, but it works fine with yet another new battery.

    before i get a bad review on the shop for thsi thing diying for the 4th time... what the hell is going on with this phone and how i can prevent it from killing itself again?

  • #2
    The only one that I ever had that had a pmic cap short was exactly like this. The pmid cap short made a lot of heat and that damaged Tigris (my guess) and the damaged Tigris was then able to kill tristar. That’s also a guess.

    What i noticed is this
    phone boots but will not charge
    change tristar. No charge
    change Tigris —charges briefly then does not charge
    change tristar again —charges briefly then dies
    find pmid cap short—does not charge
    change Tigris does not charge
    change tristar again —charges normally and is solved

    My advice is change everything all at the same time and explain to him that this is an odd case. Have the data sheet for Tigris open and point out the temperature bit. Impress him with your deep knowledge of the problem and make him understand that his failure is an odd presentation.

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    • #3
      Hi Jessa, i have rebuilt the whole damn charging circuit from donors. brand new tigris brand new tristar brand new mosfet (charging and the vcc main one) and all the main caps around the zone. the phone seems to be charging fine but it is very slow. only draws about 500mamps from lightning cable/power z both with an original charger. once the phone reaches around 85% of battery charge it basicaly stops charging. it still says "charging" but it draws little more than 100ma unless the screen is on where it jumps back to 500ma. with the phone turned off or just on standby it dows not draw more than 100ma... headache.. nothing is getting abnormally hot

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      • #4
        My advice was tristar and Tigris at the same time. After that when you have the “I stop charging at 80%” then I jump batt/vccmain mosfet to keep Tigris from opening mosfet too early.

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        • #5
          q1701? jump pin 2 to 3?

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          • #6
            Never mind wrong mosfet. The BGA one. What kind of problems can that create?

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            • Jessa_the_Professa
              Jessa_the_Professa commented
              Editing a comment
              None of us know for sure, but we can guess. My guess is that the way charging works is that tigris takes usb 5v, drops it to 4.3v and sends to vccmain. With the mosfet closed main flows through and charges the battery. When you remove usb5, then the mosfet is also closed so battery sends batt voltage to main. So when does tigris open the mosfet to shut off the connection between battery and main? Only when the battery is fully charged. If the battery voltage drops down (from chips with direct connection to vbatt), then tigris would close the mosfet to trickle charge.

              So what if you said "no, you can't open the mosfet, batt and main will be a wire. It would mean that 4.3v would always be "knocking on the battery board's door" even when the battery itself was 4.3v fully charged. Would that reduce battery life? Maybe in some theory, but practically speaking, unlikely. Is it unsafe? The battery has its own built in protection board, so I think it is fine. Any practical experience? Yes--I've done this a few dozen times and those phones never came back.

              Why would this help? The theory is that is tigris for some reason is unable to understand the battery voltage or some other regulatory input and is INAPPROPRIATELY opening the mosfet to shut off the path of current into the battery as the battery nears full charge (i.e. tigris thinks it's fully charged when it is not) then jumping the mosfet would cure that problem, at least diagnostically. If you wanted to put more time into it, you could attempt to guess WHY is tigris doing this and do some experiments to see if you could figure it out. I've never gone that far down this particular rabbit hole

              One last thing--why does the battery appear to charge when the screen is on in this scenario? It isn't charging. It just needs little to no usb5v when the screen is off, and when the screen is on it consumes the current to light up the leds through the 5v usb.

          • #7
            thank you Jessa, i did the bypass and the phone finally reached 100%. i absolutely have no time to reach the bottom of the rabbit hole these days with all the dead 7 coming in. but if it works it works. thank you again

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            • #8
              Well fuck. After a day (with the bypass done) the battery gauge goes up and down high and low and then it turns off.

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