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820-00045 a1534 wont turn on at all, not water damaged

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  • 820-00045 a1534 wont turn on at all, not water damaged

    What are the troubleshooting steps for this one if it wont power on?

    I took out the board, checked under scope, literally no water anywhere, no dents on the housing, so it seems laptop was properly used.

    The small white LED is on when i connect the charger (i have an original apple charger usb-c), i can measure 8V on the battery connector when they are connected.

    Fixed this model few times with new keyboard and new screen, but never measured the board before.

    So what measurement will i report to you?

  • #2
    also, i did not find donor board on aliexpress, only working boards for like 385eur (this is a 1.2ghz, 512gb ssd, 8gb ram model)

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    • #3
      Measure the power rails with the charger connected, battery disconnected. Which are present, which are missing?

      I would start with PP3V3R3V0_AON. Is this present? If not, what is its resistance to ground? If resistance to ground is below 350 ohms, does removing U4700 remove the short circuit?

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      • #4
        Ppdcin_e85 : 20v

        pp3v3r3v0_aon : 3.265 v

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        • #5
          ppbus g3h : 8.6V

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          • #6
            The basics look good. Check all rails for shorts to GND. I had a few with a short on 5V rail.

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            • #7
              I came back finally to this one no shorts on any rails
              PP5V_S0 = 0V
              line is not shorted to GND
              led is glowing a bit but laptop didn't take any current/charge, and doesn't turn on
              connected to power supply on battery connectors takes 0,10A nothing heating up.
              U7100 replaced
              u4700 replaced
              no luck still not working
              Any ideas ?

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              • #8
                U7100 has firmware.
                New chip will not work, you need one from donor board (same model).

                Do you get voltage on PPBUS_G3H with new chip???

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                • #9
                  Yes PPBUS_G3H present on F7140 I measured 8.05V

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                  • #10
                    8.05V is not correct value for PPBUS_G3H.
                    I suppose you checked it without battery connected.

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                    • #11
                      I have connected power supply to battery connector. Should I put back U7100 ? I have another donor board with have faulty CPU, well CPU only is heating up.

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                      • #12
                        "I have connected power supply to battery connector."
                        I'm not sure if I correctly understood you...
                        Did you connect bench power supply to battery connector, why?

                        You've got 8.6V with original U7100.
                        Did you change it in base of which reason?
                        Didn't measure more signals on the board?

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                        • #13
                          Because is easier to measure both board sides with power supply, would I will getting not right measurements with power supply ?
                          I replace ic to try maybe it will resolved issue, this was common issue so I tried replace it.
                          I didn't measure anything more so far.

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                          • #14
                            These new boards will not start untill SMC talks with the charger...
                            And never change components before some measurment indicates that.

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                            • #15
                              Problem is that the laptop is not taking charge no current taken, on old or new ic, so SMC is not talks witch charger and this U7100 is responsible for a charging as I can see on schematic

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