iMAC G5 PSU (again.. sigh)!

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  • JEWilson
    Badcaps Veteran
    • Sep 2007
    • 369
    • Scotland, United Kingdom

    #1

    iMAC G5 PSU (again.. sigh)!

    Manu - AcBel
    http://www.acbel.com.tw/eng
    Model - API4PC46
    Apple P/N - 614-0326

    System unit stuck on LED1
    Will not start
    Removed PSU, recapped
    Tested PSU out of unit post recap

    On standby
    1 : +0.028 VDC (Black)
    2 : +0.028 VDC (Black)
    3 : +0.000 VDC (Black)
    4 : +0.009 VDC (Grey/Purple)
    5 : +0.000 VDC (Black)
    6 : +0.009 VDC (Grey/Purple)
    7 : +0.000 VDC (Black)
    8 : +0.000/1 VDC PG (Blue) - swings between these two values
    9 : +5.196 VDC 5VSB (Purple)
    10 : +0.025 VDC (Brown)
    11 : +0.000 VDC (Black)
    12 : +0.028 VDC (Black)
    13 : +0.025 VDC (Brown)
    14 : +0.000 VDC (Black)
    15 : +5.196 VDC On/Off (Grey)
    16 : +0.000 VDC (Black)
    17 : +0.000 VDC (Black)
    18 : +0.000 VDC (Black)
    19 : +0.025 VDC (Brown)
    20 : +0.009 VDC (Grey/Purple)
    21 : +0.009 VDC (Grey/Purple)
    22 : +20.42 VDC (Brown)

    Jumpered 15-16
    1 : +3.332 VDC (Black), ripple 4.7mV VAC
    2 : +3.332 VDC (Black), ripple 4.7mV VAC
    3 : +0.000 VDC (Black)
    4 : +5.145 VDC (Grey/Purple), ripple 36.8mV VAC
    5 : +0.000 VDC (Black)
    6 : +5.145 VDC (Grey/Purple), ripple 36.9mV VAC
    7 : +0.000 VDC (Black)
    8 : +0.079 VDC PG (Blue), ripple 3.5mV VAC
    9 : +5.196 VDC 5VSB (Purple), ripple 3.8mV VAC
    10 : +11.970 VDC (Brown), ripple 149.9mV VAC
    11 : +0.000 VDC (Black)
    12 : +3.332 VDC (Black), ripple 4.5mV VAC
    13 : +11.970 VDC (Brown), ripple 3.5mV VAC
    14 : +0.000 VDC (Black)
    15 : +0.000 VDC On/Off (Grey), ripple 3.5mV VAC
    16 : +0.000 VDC (Black)
    17 : +0.000 VDC (Black)
    18 : +0.000 VDC (Black)
    19 : +11.970 VDC (Brown), ripple 98.3mV VAC
    20 : +5.135 VDC (Grey/Purple), ripple 32.6mV VAC
    21 : +5.135 VDC (Grey/Purple), ripple 32.8mV VAC
    22 : +23.530 VDC (Brown), ripple 270mV VAC

    Is PG 8 correct for this type of PSU?
    Anyway, put PSU back in the unit.
    Same problem, still only LED.
    Unit logic board has 1 domed 6.3V 1800uF Nichicon on the VRM O/P.
    Took the PSU out again.
    Now cannot get the PSU (15-16) to start again.
    Odd...

    Suggestions...
    Q1 on the PSU? Why would it just let go?
    Are there TopSwitches in these?
    Advice appreciated.

    Thx
  • Toasty
    Badcaps Legend
    • Jul 2007
    • 4171

    #2
    Re: iMAC G5 PSU (again.. sigh)!

    Have to fix the mainboard. That's the problem. All those Nichi's have to go. TC sells a kit, I think.

    Reduce the reports down to the basics. Every wire is not necessary.

    Look at the board and see what goes where.

    Essentially, you have 5vsb, 24vsb, ground(blacks), +3.3, +5, +12.

    If 5vsb is up, then you have 1/2 the battle solved.

    Topswitch is a -VERY RARE- failure. (how's that for a subtle hint)

    If 5vsb is there, the TOP is fine.

    Check Q1 and ZD6. What is the SB voltage @ Q1 collector?

    Have you recapped the unit, especially the 4 next to the mains caps?

    Search the forums for these either by 4PC46 or API4PC46.


    T
    veritas odium parit

    Comment

    • JEWilson
      Badcaps Veteran
      • Sep 2007
      • 369
      • Scotland, United Kingdom

      #3
      Re: iMAC G5 PSU (again.. sigh)!

      Y - recapped the PSU
      All of them except the main large can lytics for the primary and PFC
      Someone had been there before me - did part of the job

      Funny, post recap
      Got the unit to start (with 15-16 jumpered)
      Now it won't - very odd....
      So will check Q1 and ZD6 - thx

      Does the earth tag in the PSU need attachment to the PSU case?
      It was not with this PSU

      Will get the PSU right before the logic board recap

      Will check the posts as recommended

      Comment

      • Toasty
        Badcaps Legend
        • Jul 2007
        • 4171

        #4
        Re: iMAC G5 PSU (again.. sigh)!

        >> Does the earth tag in the PSU need attachment to the PSU case? <<

        Not sure what you mean by that question.
        If you mean the ground wire coming from the socket, then yes. Once the board is installed back in the case, that wire goes to the PSU case on the nearby tab.

        Your voltages all look(ed) good.

        Need that collector voltage on Q1 at standby. ~16v

        Make sure you're measuring from the HOT side (-)

        T
        veritas odium parit

        Comment

        • JEWilson
          Badcaps Veteran
          • Sep 2007
          • 369
          • Scotland, United Kingdom

          #5
          Re: iMAC G5 PSU (again.. sigh)!

          Update

          This unit had a bad Q1
          I replaced D2 and ZD6 anyway
          Replaced Q1 with a 350mW part

          Seems to be ok again

          Now... load testing
          Any thoughts on using an ATX go/no go PSU tester
          with the cables mapped to the Apple PSU?

          Ok... before people start saying no; this is just for
          future use with these PSU, before, that is,
          I get my hands dirty

          How would you handle 24V on an ATX tester

          Comment

          • Toasty
            Badcaps Legend
            • Jul 2007
            • 4171

            #6
            Re: iMAC G5 PSU (again.. sigh)!

            Parts used? Numbers? Supplier?

            You could rewire the connector I'm sure. Or make up a "patch" one to use it on either. Grab the male connector from an old mobo and the female from a trash PSU and wire it for the Apples.

            The 24v would be a matter of a resistor or Zener with a LED or 2. Remember that on some of these, the 24v line doesn't come up full until the unit is running. It sits around 19-20v in standby.

            T
            veritas odium parit

            Comment

            • JEWilson
              Badcaps Veteran
              • Sep 2007
              • 369
              • Scotland, United Kingdom

              #7
              Re: iMAC G5 PSU (again.. sigh)!

              Ok

              Zener ZD6 - NXP BZV55-B16,115, Mouser P/N - 771-BZV55-B16115
              Diode D2 - Fairchild FDLL4148_D87Z, Mouser P/N - 512-FDLL4148D87Z
              Transistor Q1 - Fairchild MMBT2222A, Mouser P/N - 512-MMBT2222A

              Thx

              Comment

              • Toasty
                Badcaps Legend
                • Jul 2007
                • 4171

                #8
                Re: iMAC G5 PSU (again.. sigh)!

                Have you been using that Zener with success?

                T
                veritas odium parit

                Comment

                • JEWilson
                  Badcaps Veteran
                  • Sep 2007
                  • 369
                  • Scotland, United Kingdom

                  #9
                  Re: iMAC G5 PSU (again.. sigh)!

                  Well....

                  This is the first time I have used this part
                  So.. we will see if it does the trick
                  Will do load testing and see how this plays out

                  Have another of the same PSU model (and got a working delta)
                  What would you typically use for ZD6?

                  Comment

                  • Toasty
                    Badcaps Legend
                    • Jul 2007
                    • 4171

                    #10
                    Re: iMAC G5 PSU (again.. sigh)!

                    I was curious as to how you arrived at a 16v zener. Did you test a good part or go by the color coding?

                    T
                    veritas odium parit

                    Comment

                    • JEWilson
                      Badcaps Veteran
                      • Sep 2007
                      • 369
                      • Scotland, United Kingdom

                      #11
                      Re: iMAC G5 PSU (again.. sigh)!

                      No code

                      No Test

                      Took your word for it (found it in the forum)

                      Thx

                      Comment

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