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6s + No service

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  • #1

    6s + No service

    I have a 6s+ in immaculate condition with a no service issue, the gentleman is an older fellow and has looked after the phone really well. The device looks to have no bends (under my level) and no signs of a drop.
    The phone has never been opened and according to him just lost service one day so gives me no start point.

    I have checked imei, carrier, serial etc in settings and all are present. I have done a visual inspection of the rf area (both sides) checked for dead shorts, checked for odd diode readings and couldn't see anything.
    So i looked at bb_pmu (u_pmu_rf) as i have had issues in past with this, and rebelled in case of dry solder joint or cracks, this brought the service back and customer went away happy, after 2 weeks the same happened so I thought maybe the fault was the chip so changed the chip again this worked for a few days this time and the same happened.

    My thinking is I'm inadvertently "re-hotting" one of the ics in the general area, probably bb_cpu (as directly on other side) causing the tempory "fix".

    My question is, is there any tests I can do to bb_cpu before I lift to reball or any other known culprits that could be an issue. The problem goes away with heat to that area so im thinking a pad/ic or joint is to blame.


    Tags: None
  • #2
    Try Pressing on bb_cpu. Put it in offline mode and back and see if service comes back.

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    • #3
      Clamp and test, its strange how things slip your mind i used to use this method on xbox 360 gpu to test. Thanks for brain poke lol will try tomorrow
      • Likes 1

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      • #4
        I tried that and no luck, the worst thing is its intermittent as was on most of the morning, I have done some diode mode readings around the bb CPU while its no service and the PP_0V9_SMPS1 is reading low (0.090) I am not sure if that's normal but I don't recall seeing a normal line that low. If this line is to blame it would make sense as its the power rail to the MSM modem.
        I have never changed BB CPU am I right in thinking these are twinned with the board and not replaceable? is there anything I can do before lifting CPU to test line to see if it is the ic?

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        • crea2k
          #4.1
          crea2k commented
          02-14-2018, 05:20 PM
          Editing a comment
          Well it is technically replaceable if you have one of the programmers from china, they also sell blank ics on aliexpress but you need a programmer to program them which arnt cheap.

          It may not be bb_cpu though. It's possible it's a line running from it to other parts of the board and through thermal contraction / expansion it's connecting and disconnecting the traces.

          When it goes no service is modem firmware still showing in settings, general, about ?.

          Like jessa says there is so many things it may be, that's the problem. If you could pin it down to bb_cpu you could concentrate on that but it may also be one of the ics relating to signal also.
        • crea2k
          #4.2
          crea2k commented
          02-14-2018, 05:25 PM
          Editing a comment
          If that voltage is low it's possible the bb_pmic is bad as that lines appears to just go between bb_cpu and bb pmic
      • #5
        Funny, I had a local guy come in with searching no service on a 5c last night---same history, beautiful board and it just stopped working. I told him these problems are too open-ended to put time into because there are 20 pages of schematics for searching no service issues and no visual indicators of the problem. The board has to be able to tell us where it hurts. I'm always a softie for my local peeps, so while he took a long phone call explaining to an old friend that his Dad was on hospice and about to die, I pulled board and bottom shield, reflowed bbpmic and reassembled. Service came back so that I could get him out of activation wizard (carrier store of course did restore which bricked the phone). I told him that his phone was now on hospice too. Reflow isn't repair so this problem will come back, I don't know if it will be in a day or a month so I can't charge you for work I can't warranty and sent him on his way.

        I would do the same for this phone---its a good way to get a good review if you're slow.
        • Likes 1

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        • #6
          crea2k Modem firmware all there and still had service, I replaced bb_pmic twice to rule out bad ic's so I have decided to take Jessa's advice as my fuck it threshold was getting extremely close anyway,i just didn't want to miss something stupid.
          Thanks for the help guys it's always appreciated.
          • Likes 1

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          • #7
            Sounds like a plan, some jobs just need to go away otherwise they eat all your time up.

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