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problem with Delta GPS750AB A PSU. No +5v VSB

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    #41
    Re: problem with Delta GPS750AB A PSU. No +5v VSB

    Well, that is true RJ… That’s why I suggested a PSU as well.

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      #42
      Re: problem with Delta GPS750AB A PSU. No +5v VSB

      I found a nice video from LER explaining how an ATX power supply works. The older ones and the newer ones. Pretty well done!
      https://www.youtube.com/watch?v=GjZtZNssroE

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        #43
        Re: problem with Delta GPS750AB A PSU. No +5v VSB

        The videos are nice I'm a long time subscriber.

        I have removed relay and one suspect choke, still the sound remains when PSU is started even without relay. I mean it does not start but sound still can be heared.

        I applied enamel coating on all chokes, maybe that will fix it.

        All line are working +12 +5 -12 +3.3 +5VSB
        Last edited by smile; 05-03-2022, 08:24 AM.

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          #44
          Re: problem with Delta GPS750AB A PSU. No +5v VSB

          Enamel coating dried but chirping is not gone.
          I connected PSU to test board, about 250W load. It works runs benchmarks no problems.
          However the chirping sound gets faster and faster with load.

          Voltages are OK.

          Very strange i double checked caps and my esr meters (2 of them) say all caps good including 2 big ones.
          two big ones are 330uF and I measure 300uF, esr is within spec not more then 0.1Ohms
          I connected anothe 220uF cap and it seems the cycle increased (without scope that is hard to say), so that confirms it's PFC circuit????

          PSU does not chirp until started so it's not +5VSB circuit? NOT PFC circuit, but then what chirps if I removed starting relay and when started it chirps, obviously no voltages are working with removed relay except +5vsb
          Last edited by smile; 05-03-2022, 02:42 PM.

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            #45
            Re: problem with Delta GPS750AB A PSU. No +5v VSB

            Those 2 big caps won’t get rid of your chirping. Take a dry wooden spoon to your ear and see if you can pin point it. My guess is that big transformer.

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