How to test ac transformer secondary output?

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  • JimBanville
    Senior Member
    • Aug 2020
    • 118
    • United States

    #1

    How to test ac transformer secondary output?

    Can someone please look at this photo and tell me how I would test the voltage of the 6 wires coming out of this ac transformer? Thanks!!
    Attached Files
  • R_J
    Badcaps Legend
    • Jun 2012
    • 9517
    • Canada

    #2
    Re: How to test ac transformer secondary output?

    The black should be the center tap of the purple and green wires, so you can check the voltage between the purple and green for the full secondary voltage or check between black and either purple or green.
    I would need to see the bottom of the pc board to be sure that the black is the center tap. The other set of wires should be checked the same way (Red center tap?)

    I said this before I saw the circuit board, so this is not correct in this case.

    The Blue wire is the center tap and the Red and Brown feed the diodes.
    The Black feeds a diode for a negative voltage so it is likely that either Green or Purple goes to ground and the other feeds another diode somewhere?
    Last edited by R_J; 01-01-2021, 07:13 PM.

    Comment

    • JimBanville
      Senior Member
      • Aug 2020
      • 118
      • United States

      #3
      Re: How to test ac transformer secondary output?

      Originally posted by R_J
      The black should be the center tap of the purple and green wires, so you can check the voltage between the purple and green for the full secondary voltage or check between black and either purple or green.
      I would need to see the bottom of the pc board to be sure that the black is the center tap. The other set of wires should be checked the same way (Red center tap?)
      Thanks! This picture should be a mirror image of the top of the board...
      Attached Files

      Comment

      • R_J
        Badcaps Legend
        • Jun 2012
        • 9517
        • Canada

        #4
        Re: How to test ac transformer secondary output?

        Looks like the Blue wire is the center tap and the Red and Brown feed the diodes.
        The Black feeds a diode for a negative voltage so it is likely that either Green or Purple goes to ground and the other feeds another diode somewhere?

        What is it you are trying to do? just check if the transformer is working?
        Last edited by R_J; 01-01-2021, 07:16 PM.

        Comment

        • JimBanville
          Senior Member
          • Aug 2020
          • 118
          • United States

          #5
          Re: How to test ac transformer secondary output?

          Originally posted by R_J
          Looks like the Blue wire is the center tap and the Red and Brown feed the diodes.
          The Black feeds a diode for a negative voltage so it is likely that either Green or Purple goes to ground and the other feeds another diode somewhere?

          What is it you are trying to do? just check if the transformer is working?
          Yes...the CD player won't power on. Power switch works and I have 120v ac at the output of the power switch pcb. I figured checking the output of the transformer was the next logical step.
          My main concern is damaging something by testing voltages between any of these 6 wires. Is that a concern? Thanks for the help
          Last edited by JimBanville; 01-01-2021, 07:44 PM.

          Comment

          • JimBanville
            Senior Member
            • Aug 2020
            • 118
            • United States

            #6
            Re: How to test ac transformer secondary output?

            Originally posted by R_J
            Looks like the Blue wire is the center tap and the Red and Brown feed the diodes.
            The Black feeds a diode for a negative voltage so it is likely that either Green or Purple goes to ground and the other feeds another diode somewhere?

            What is it you are trying to do? just check if the transformer is working?
            Here's the service manual ...

            Comment

            • R_J
              Badcaps Legend
              • Jun 2012
              • 9517
              • Canada

              #7
              Re: How to test ac transformer secondary output?

              How many threads do you have for this unit? stick to one thread.
              Last edited by R_J; 01-01-2021, 08:05 PM.

              Comment

              • JimBanville
                Senior Member
                • Aug 2020
                • 118
                • United States

                #8
                Re: How to test ac transformer secondary output?

                Originally posted by R_J
                How many threads do you have for this unit? stick to one thread.
                Sorry, but I wasn't getting any useful help in the other thread. I'll delete that one.

                Comment

                • R_J
                  Badcaps Legend
                  • Jun 2012
                  • 9517
                  • Canada

                  #9
                  Re: How to test ac transformer secondary output?

                  Originally posted by JimBanville
                  Sorry, but I wasn't getting any useful help in the other thread. I'll delete that one.
                  If what I provided was not helpful I will stop helping

                  Comment

                  • JimBanville
                    Senior Member
                    • Aug 2020
                    • 118
                    • United States

                    #10
                    Re: How to test ac transformer secondary output?

                    Originally posted by R_J
                    If what I provided was not helpful I will stop helping
                    Sorry. No disrespect intended, but I was getting such general/vague info. I'm competent enough to follow direct instructions, like "place dmm - lead at this point and dmm + lead at this point", but just telling me to check voltages leaves to much room for error. I deeply appreciate any help I can get!! Seriously.

                    Comment

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