Mac mini 2018

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  • Pragmatiko
    Badcaps Veteran
    • Jul 2013
    • 468
    • IT

    #1

    Mac mini 2018

    Hi all, did you solved? I have same identical problem but I have PP5V_G3S 5V

    PP1V_PRIM 0V
    PP1V2_PRIM 0V

    led of Mac Mini is blinking
  • mon2
    Badcaps Legend
    • Dec 2019
    • 13829
    • Canada

    #2
    Pragmatiko - with no power , measure the resistance (not diode mode) to ground of PP1V_PRIM and the PP1V2_PRIM rails. Post your measurements.

    Comment

    • Pragmatiko
      Badcaps Veteran
      • Jul 2013
      • 468
      • IT

      #3
      Hello,
      on PP1V_PRIM 46ohm, and PP1V2_PRIM 5Kohm

      Tks

      Comment

      • mon2
        Badcaps Legend
        • Dec 2019
        • 13829
        • Canada

        #4
        What is the history of your unit? Just stopped working one day? Any liquid damage? This model appears to be plagued with the same fault.

        PP1V_PRIM @ 46 ohms, to me, sounds too low for a normal logic board. This rail is also used to power the USB PHY.

        Carefully, measure the voltage to ground of:

        PMU_P5V_USBC_ISENSE
        PMU_P5V_USBA_ISENSE

        PP5V_G3S_USBA
        PP5V_G3S_USBC
        PP3V3_G3S_WLANBT
        PP3V3_G3H_ENET

        Comment

        • Pragmatiko
          Badcaps Veteran
          • Jul 2013
          • 468
          • IT

          #5
          no liquid damage. I got it from a friend that says the unit stop to working. Now when i plug it i can see only led to blinking. i will che the voltage you suggested me and reply to you soon.

          Comment

          • Pragmatiko
            Badcaps Veteran
            • Jul 2013
            • 468
            • IT

            #6
            Originally posted by mon2
            What is the history of your unit? Just stopped working one day? Any liquid damage? This model appears to be plagued with the same fault.

            PP1V_PRIM @ 46 ohms, to me, sounds too low for a normal logic board. This rail is also used to power the USB PHY.

            Carefully, measure the voltage to ground of:

            PMU_P5V_USBC_ISENSE voltage not present
            PMU_P5V_USBA_ISENSE voltage not present

            PP5V_G3S_USBA voltage present 5V
            PP5V_G3S_USBC voltage present 5V
            PP3V3_G3S_WLANBT voltage present 3,3V
            PP3V3_G3H_ENET voltege present 3,3V

            please read above

            Comment

            • Pragmatiko
              Badcaps Veteran
              • Jul 2013
              • 468
              • IT

              #7
              update, i have removed L7821 and L7822 and now voltage side IC is present. Then i suppose that 44ohm resistance downstream coil is not good.

              Comment

              • mon2
                Badcaps Legend
                • Dec 2019
                • 13829
                • Canada

                #8
                Can you clarify? There is still a FB connection resistor @ R7820. Carefully remove it. Do not power up without these components. Great that you are comfortable with this process as the parts are incredibly small. There is also a cluster of pins on U7800 that directly bond to this rail (R12, T12, etc.) - so U7800 is still a suspect.


                Then confirm which side of this rail is shorted? Is it the producer (U7800) or consumer side. In your post, do share the pin # of the removed coil(s) that show the 44 ohms to ground.

                One tool that would help here and we are considering it to source soon is a low ESR capacitance meter that can measure in milli-ohms. With such a tool, it should be possible to test each cap or whatever on the board to confirm if it is shorted or not. There is a sea of parts onboard to investigate.

                Comment

                • Pragmatiko
                  Badcaps Veteran
                  • Jul 2013
                  • 468
                  • IT

                  #9
                  Well,I removed R7820 too and still I have low resistance consumer side. There are a lot of capacitor on that PP1V_PRIM. I will try to test with ESR meter (tomorrow maybe). Thank you for your support.
                  Attached Files

                  Comment

                  • mon2
                    Badcaps Legend
                    • Dec 2019
                    • 13829
                    • Canada

                    #10
                    There is also a cluster of pins on U7800 that directly bond to this rail (R12, T12, etc.) - so U7800 is still a suspect.​

                    Really interested to hear of your test results with the ESR meter. It is on my wish list. There is an excellent YT video on this topic and it is a no brainer to justify the purchase. Just scouting for a good quality one at a fair price.

                    Comment

                    • Pragmatiko
                      Badcaps Veteran
                      • Jul 2013
                      • 468
                      • IT

                      #11
                      Originally posted by mon2
                      There is also a cluster of pins on U7800 that directly bond to this rail (R12, T12, etc.) - so U7800 is still a suspect.​

                      Really interested to hear of your test results with the ESR meter. It is on my wish list. There is an excellent YT video on this topic and it is a no brainer to justify the purchase. Just scouting for a good quality one at a fair price.
                      I don't know why, but I strongly believe that the problem is on R12,T12,U12..... of U7800 ic.
                      I've checked all capacitor under microscope. Usually bad capacitor is visible. I would be tempted to desolder the U7800.

                      Comment

                      • Pragmatiko
                        Badcaps Veteran
                        • Jul 2013
                        • 468
                        • IT

                        #12
                        Found cause of low resistance. I've removed U1200.
                        Now I don't have low resistance but still I don't have PP1V_PRIM. Maybe cause is PCH not installed?

                        But I think 44ohm is normal value for PCH. There must be more
                        Last edited by Pragmatiko; 05-20-2024, 06:13 AM.

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