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Iphone 6 No Service

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  • Iphone 6 No Service

    Phone goes from mobile network detection to no service and searching. Can go back again to receive the mobile network and could stay liker that for a day or two

    Will not receive or send mobile phones calls sometimes just rings out when mobile network showing a strong signal

    No issues with mobile network. Works perfect in a know good board

    Transferred the logic board to a know good iPhone 6 phone with everything working perfect

    Was getting the same issue on the known good board


    Where to start??

    Thank You

  • #2
    Remove the shield from the baseband area, then try pressing down on the baseband cpu. Try flipping the phone onto offline mode and back. If the signal comes back with you pressing on the bb_cpu it needs reballing / pulled pads.

    Also when it's searching / no signal, if you go into settings, about is modem firmware listed ?.

    you can also try a factory reset with iTunes and then examine the restore log. If it's failing on the baseband cpu it will tell you in the update log.

    Its either a bb_cpu problem or one of the many signal processing chips problem, you need to figure out which.


    • #3
      When it is searching for service if you type star hash 06 hash into the phone keypad does it show the imei number. If it doesn't then its a good chance its baseband. If it shows an imei number I would first start to examine U_VLBPAD for scorch marks.


      • #4
        Stayboe How is the U_VLBPA related to the no service The IMEI number their no problem. The situation it can work normal even for a few days and then can get searching or no service

        The mobile network used is fine has it is the one I use myself and tested it with my own SIM card and still the same problem

        I have done all the software test like has you say crea2k resetting it to factory settings. reset network and updates

        So it is a logic board issue has also transferred the board to a know good casting


        • #5
          There is a heap of stuff under the bottom shield that can cause no service. Did you try putting pressure on baseband like crea2K suggested. Sometimes you have to wait about 30 seconds for it to pick up service. I had one last week which was sent to me for searching no service but when I put my sim in it got service. I had it three days and it still had service. I put it in the glove box and went shopping when I returned I tried calling it but nothing I thought it couldn't get service in the glove box so I took it out and it was searching. That night it was fine again. I put it out in sun the next day and it went back to searching which made me think it is probably a loose pad under a chip and the change in temperature causes it. After putting pressure on the chip that I thought was the problem it got service back, but not straight away it can take up to 30 seconds so be patient.


          • #6
            A good test for intermittent phones is the following :
            i also do screen refurbishing so have a hot plate, I put the phone on the hot plate at 70 degrees until it's fairy hot, try your problem then. Then once it's cooled down to room temp you can try giving the back of the phone a good dowse in freeze spray for a few seconds.

            iv got a 7 in with audio ic failure and if I cool the board right down it starts working fine. Heat it up and it stops working, so proven bad joint.


            • #7
              For most iPhone system problems there are two to three pages of schematics that could every component, connector, and chip for the entire system. For the system of cellular service---there are TWENTY PAGES of schematics----so troubleshooting board level searching no service faults can be a huge rabbit hole.

              It will be too laborious to attempt to measure the hundreds or thousands of connections required for baseband to work. You can either say "forget this" and not put any time into it, or you can start by addressing the signature problem with is bb_cpu. Since bb_cpu can't be replaced (it is unique to the board) then reball it, and add the long jumper and see if that solves. Like everyone else has suggested---if you knew in advance that pressing on bb_cpu would bring back service, then it would be a lot more reasonable to attempt the reball. If pressure did NOT bring back service, then odds go down that reball will solve.