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Ipad airs in general that wont charge

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  • crea2k
    replied
    Thanks !, that was actually my next plan of action before I just bunged a micro battery charger board in a housing and called it fixed. There is the two mosfets, one nearest the pmic seems to let the charge current through and the other is possibly to do with battery and I think is hooked into the current sense line.

    Id change the pmic but it's way to expensive on the airs as the pmic itself is about £40 / $35 where as you can buy like 5x iPad Air 2 pmic for that, it's crazy !.

    if the mosfets don't fix it il just bung a battery manager board in it and dispose of it on eBay. Least it'll charge with one of those in it, it just won't bong when plugged in to charge.

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  • Jessa_the_Professa
    replied
    Change pmic, see what happens. In the Air and mini retina the 5v goes to pmic where charging happens. If you’ve ruled out “I have power and I have data” then next is bad chip. This sounds like the 5c where it gets a defect at the batt-main mosfet and then has state specific charging. Jumping the mosfet solves, but here the mosfet may be internal to the pmic. If not, I’d find the mosfet and jump it before changing pmic

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  • crea2k
    replied
    Just looking on gsm forum and someone reported charging the pmic and it fixed the problem. I'm really leaning towards the pmic now as the other person that posted about the mini 2 on here doing exactly the same thing and doesn't that use the same pmic as the air ?. Just all suggests a problem with the pmic itself from what I can see.

    http://forum.gsmhosting.com/vbb/f631...r-1-a-1994070/

    if i remove the first large ferrite / filter in the USB power line near the home button connector I get 5 volts through from the charger. Solder it back I get 3.8 volts.

    if I hook the dtps into that line and give it 5 volts it registers as 4.99 volts at the cap on the other side of the first mosfet and pulls zero amps so it's not shorted at all. That is with the iPad turned off and battery disconnected.

    if I hook a dtps into that ferrite near the home button connector whilst the iPad is plugged into charge to try and boost the current more, the iPad doesn't start charging.

    the iPad still continues to charge fine when turned off.

    when charging when turned off the voltage at that ferrite is 4.19volts with it charging at 1.18 amps at 50% battery. Turn on the iPad and this drops to 3.8volts and charging stops. This difference in voltage at that ferrite is 100% inline with several ipad airs iv seen with this problem before.
    Last edited by crea2k; 12-11-2017, 05:00 PM.

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  • crea2k
    replied
    So this one gets weirder..... iv replaced tristar, this made no difference, I replaced the charge port , also no difference. One thing I have noticed though is the charge current coming down the cable is 3.8volts when it should be 5volts. So it's like it's hitting a wall that drops the voltage down on the line.
    we now the charge cable and charger is good as it charges everything else just fine.
    i scratched away on the back of the charging flex of the iPad and also took readings on the board and it's 3.8volts. If you unsolder the dock from the board then take readings on the dock it's 5 volts so the dock is fine.

    the iPad turns on, and will charge for the first couple of seconds when turned off before it prompts to boot. Turning it off when booted will enable it to charge fine.

    known good batteries have been tried with the same result.

    Sodering the pads to the battery yielded no results.

    The only problem I see is that low voltage on the Ferrite for USB power, everything else has been checked out, so totally clueless now.

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  • Jessa_the_Professa
    replied
    I feel like I read here that the iPad would charge but then not detect the cable after plug/unplug. That may have been a different post, but if true then that points to the usb side recognition/verification fault such as the interrupt line on tristar

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  • crea2k
    replied
    No the charge port and tristar are the next things to change.

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  • Jessa_the_Professa
    replied
    Ok—so state the exact problem with this iPad —the original problem seems to be generic.

    have you changed the charge port and flex and Tristan?

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  • crea2k
    replied
    Ok so iv tried two different batteries that work with other Ipads, and get the same result, so we know the batteries arnt the problem. Iv also tried soldering the line directly to the battery and that doesn't work either so that rules the connection out.

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  • crea2k
    replied
    Thanks, just bought two new batteries so il have a look and test

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  • Jessa_the_Professa
    replied
    You also want to rule out bad internal data lines on the battery itself by using a battery that is known good that can be charged by another air board normally

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  • crea2k
    replied
    Ok thanks, I may try soldering a jumper from that battery line to the line on the board and see what happens. Will rule that one out then.

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  • Jessa_the_Professa
    replied
    Personally we almost never see any Airs that have never been opened because nearly all of our work comes from other shops. But on the short list of “things that can just go bad” I would rank a critical connection that is very thin between battery and board that is not soldered but only held in place by a screw as highly likely to be a failure point as would battery stopped providing accurate current sensing data.

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  • crea2k
    replied
    Do you see this even on the genuine ones that have never been opened ?

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  • Jessa_the_Professa
    replied
    Yes! Look at it—how easy would it be to get a poor connection on that line? And the line continues into the battery itself. A LOT of the replacement batteries have either no testing done on the battery data lines, or have adhesive or weirdness that make it difficult or impossible to get that perfect alignment that we now can see is crucial.

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  • crea2k
    replied
    The battery connector itself ?, that's about the most likely candidate surely as that's the only part if the circuit that can move.

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