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A1466 820-00165 No Power

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    #1

    A1466 820-00165 No Power

    Hi. Have an A1466 820-00165 unit with no power / no fan / no chime. Magsafe light goes green / orange cycling. No liquid damage indicators, looks quite clean and not serviced by anyone (yet).

    Found that there is no PPBUS_G3H rail. Then noted that 8A fuse @ F7140 is blown. Fuse Pin 1 @ 8v6; Pin 2 @ 0v. That fuse arrived yesterday (Belfuse Fast Blow @ 8A). Replaced with great excitement but now, the rail is about 0v5v and the fuse is still intact.

    Have removed the wifi card; removed the SSD; removed the battery. Swapped out the DC / audio board with another - no difference.

    Do feel some warmth around L7130 but do not (yet) own a thermal camera.

    Any ideas?

    Suspecting that something after the PPBUS_G3H is causing excessive current draw and this power supply (U7100) is shutting down.

    Bad cap downstream?

    Also, a bit confused on what is the expected power rail here. This chassis has 8v6 for PPBUS_G3H (thanks Piernov for the clarity - schematic is not accurate) - when the fuse was OPEN. Yet another tech posted for the same logic board, they have 12v6 on this rail. Can remove the fuse again to confirm that U7100 is still good.

    With the new fuse (8A) installed, see 16.xx volts (from magsafe) @ R7005 and this is feeding into the buck converter for the 3v42 rail just fine. But R7006 is @ 0v5 (PPBUS_G3H).

    Welcome suggestions. We did recently purchase the Sunshine voltage injector but honestly afraid to use it. Also brought in some of the 'smokey flux' they show in their demos.
    Tags: None
    #2
    Re: A1466 820-00165 No Power

    All airs has 8.6v on ppbus_g3h. 12.6v is on macbook Pro's.
    How many ohms to ground on ppbus_g3h? Fuse blow because of reason, i bet that something is shorting ppbus. Check ohms, after that inject 1v to ppbus and check how many amps it is using. one of caps probably will be shorted and will go hot. tou can feel that with fingers. Make sure that ppbus would use about 3 wats, then it is easy to feel hot spot .

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      #3
      Re: A1466 820-00165 No Power

      Awesome - thank you so much for your comments. Will remove the fresh fuse, confirm that the PPBUS_G3H power supply is still working (very confident that it is). Then will break open the Sunshine tool - was looking forward to using this gadget Will report back.

      Comment

        #4
        Re: A1466 820-00165 No Power

        A blown fuse on a MAC Book!? That's almost unheard of!!! Jokes aside, as mentioned by zpi, its most likely a short somewhere on that line. Before injecting voltage, do a visual inspection first. Check for cracks on the bigger black caps or the small smd brown caps (the small ones usually discolor and might be greyish brown.

        If you cant find anything visually, then inject voltage and feel for heat spots. As mentioned, start not more than 1V 1A, then gradually raise the current. I usually start at 0.8 - 0.9V in case its a shorted high side mosfet connected to CPU.

        Comment

          #5
          Re: A1466 820-00165 No Power

          Firstly just measure ppbus to ground in ohms.

          Comment

            #6
            Re: A1466 820-00165 No Power

            0.217 to 0.25 ohms @ smd fuse to ground.

            Comment

              #7
              Re: A1466 820-00165 No Power

              So its dead short, inject 1 voltage and find hotspot, let us know how many amps ppbus is drawing when 1v is injected.

              Comment

                #8
                Re: A1466 820-00165 No Power

                Hi. Have the Sunshine TS-30 tool here which I believe is fixed to output @ 30A?

                Dialed up to 1.0v which is about 0.95-0.98v according to our 6 digit VM which I trust more than this injector.

                With black to ground; red probe of injector to the PPBUS_3v3H pin (no fuse), see a spark upon mating and values like 3A-8A but I am removing it after a pulse of this energy.

                Should we keep the voltage on for a long period?

                Now that the fuse is removed for this testing, the PPBUS_3v3H is @ 8v6 at the switcher power supply.

                Comment

                  #9
                  Re: A1466 820-00165 No Power

                  Almost ready to celebrate with non-alcoholic drinks...placed some alcohol onto assorted tantalums and applied the probes (TS-30A) - saw the alcohol evaporate on one of the caps. Two of us saw the same cap heat up and dry up very quickly. Removed this single cap and now see a resistance of 20k or so

                  Will apply the fuse back on and report back.

                  So so so exciting. Knowledge is KING. Thank you again.

                  Comment

                    #10
                    Re: A1466 820-00165 No Power

                    Hi. Ok, attached the DC / Audio board and if the large L-shaped flat cable is NOT connected, the logic board is spinning the fan This is very positive.

                    I am pretty sure that the video will work but have not yet attached the LVDS cable but will do so before leaving for the evening.

                    If we attach the L-shaped cable - the fan does NOT spin.

                    Any idea on what could be cause? We do have a known-good DC board in transit from Shenzhen but thought we could use this unit to fix another which has the same issue - the fan will not spin with L-shaped cable. Now have 2 logic boards like this. Both need fresh dc/audio boards?

                    Comment

                      #11
                      Re: A1466 820-00165 No Power

                      Attached the video cable - the machine works!!!!!! Have a login screen.

                      The L-shaped cable is OFF. Will try with it on. Could it be that we have the keyboard disconnected?

                      Comment

                        #12
                        Re: A1466 820-00165 No Power

                        Needs a genuine Apple Magsafe2.
                        OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                        Comment

                          #13
                          Re: A1466 820-00165 No Power

                          Hi piernov. Thank you for your feedback. So the external power adapter is causing the grief that we are bypassing by removing the L-shaped cable?

                          Wow. Honestly do not know the history of this external adapter.

                          Funny enough, studying the single wire protocol that is used by Apple for the hand-shake. More on that later.

                          Will search for a better external adapter.

                          Thank you!!

                          Comment

                            #14
                            Re: A1466 820-00165 No Power

                            Might also be worth checking if there is any bent pins/debris on the connectors.

                            Comment

                              #15
                              Re: A1466 820-00165 No Power

                              We had another adapter but been informed that all of our adapters are original. Apparently bought from Apple online. The 2nd adapter after 2-3 attempts, powers on the unit WITH the L-shaped cable attached. Will keep testing. Thanks.

                              Comment

                                #16
                                Re: A1466 820-00165 No Power

                                For future readers, it was C7584 (tantalum) that was heating up and was causing this short-circuit event. Will order some fresh ones from Arrow.
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