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Galaxy S7 Edge Uk

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  • Galaxy S7 Edge Uk

    Have been watching youtube video's for many months in order to learn how to repair samsung logic boards. I have always toyed around with electronics and find the miniturisation in phones facinating. Many of the repairs are started by attempting to power up the boards directly onto the battery connector with a 4.2 volt power supply. As that board connector also supplies information via two data lines from a battery to the main processor how can the board hope to boot up without any battery data being transmitted to the processor? There is also great emphasis on finding shorted components IC's /caps by finding hot components. I have working boards for reference with shield removed where power IC'get so hot that they are extremely hot to the touch and radiate their heat to surrounding components so diagnosis by this method on a faulty board is extremely difficult. I was wondering whether this is limited to samsung and Iphone components on working phones are much cooler.

  • #2
    no. we use the same techniques for samsung as we do for iPhone. Once you are extremely proficient at iPhone board repair, you apply a lot of the knowledge base to Samsung problems where we have to recognize circuitry by pattens and inference based on deeper understanding of the way mobile phones generally work from iPhones

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    • #3
      I am quite good at reballing but I have to replace a chip with a new one. I have noticed that the balls on a new chip appear to be somewhat smaller than those made with a stencil. The new chip has that horrible lead free solder and although I have put low melting point on the pads am I better off to leave the new chip as it is or re-ball with low melting point. Bit of advice will oblige as I really dont like heating chips to high temperatures. Kind Regards

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      • #4
        You can reball, but that is probably not necessary

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        • #5
          I have bought a number of ‘dead’ Samsung Galaxy S7 edge logic boards to try to learn how to mend them in order to mend an important logic board of my own.
          They all seem to suffer from the same type of problem in that when connected to a power supply none of them draw any current so there are no shorts evident. When all of them are prompted to ‘boot’ they immediately draw circa 300m/a and that then remains stable but there is no evidence of any significant heat from any components. The main PMIC’s warm up but not excessively.
          If I monitor the current draw on a working S7 edge board on ‘boot’ up the current draw starts at about 300 m/a and then as the boot process continues the current draw varies until boot has completed when the draw stabilises . All as one might expect.
          What I cannot rationalise is whether the boot process is in fact starting but stalling on the bad board either because of failures in the CPU or whether the boot process can stall because of ‘say’ a faulty video chip not responding to the CPU. Is it also possible that a faulty main PMIC does not make the necessary output to other chips on the board and the CPU does not continue with the ‘boot’ as a result?
          I am not asking anyone to look into a crystal ball but am trying to establish how the boot process normally proceeds i.e. the hand shaking processes Prompt to boot. CPU – Pmic—video chip – etc etc.

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          • #6
            In our experience these are all bad UFS chip. Sometimes you can get one to boot in the freezer. You may be able to confirm the hot spot on the memory on the edge by the CPU. We confirmed this by transplanting good CPU+UFS chip combinations onto these board and they work, and transplanting the bad ones to good board and they are in this same state

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            • #7
              Thanks for your help Jessa. Having watched many youtube streams taking off CPU’s with underfill using thin blades is not for the faint hearted especially if it cannot be determined if the chip is faulty in the first place. Many people seem to pull a lot of pads in the process of removal. Zxw shows many test points on a Samsung S7 G935f board but unfortunately it does not give any voltages or tell you if they are data points in which case a scope might indicate if the processors /memory were working. On the net I note that there may be JTAG points that might tell if the processor was working but it needs a special box to connect to I believe. I think I need to find a block diagram of the board which might indicate the boot process/sequence in detail. Only other way is to change all the power management chips and screen chips and do things by an elimination method. Hopefully If I could mend one board I might find one of your ‘signature’ faults. Kind Regards and thanks again for your input.

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              • #8
                I understand from watching some youtube streams that with Samsung S7 and S7 edge logic boards that if the input current on boot stabilises at around 50 m/a then the likely cause is a low output from one of the pins of the main ap pmic IC reference u7000. My qustion is that if the low output pin is identified at say 0.6v when it should be minimum 1.0v what prevents injecting 1v from an external power supply? If this were a solution you could identify with certainty if the IC was at fault if the boot sequence continued.

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                • #9
                  Other than timing of the signal that’s a perfectly fine strategy

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