ATX PSU Testing

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  • bigbeark
    Badcaps Veteran
    • Jan 2010
    • 661
    • Canada
    #1

    ATX PSU Testing

    I have a 350w Dynex PSU that I screwed up while testing floppy drives. The one I tested had a short and there were sparks! The PSU now lacks enough power to boot, although the PSU tester says it's OK.

    I want to test the various outputs. I understand that if I ground the green wire to a black wire on the ATX plug, and connect a hard drive to provide a load, I can run the PSU withou a motherboard and probe the outputs using an ammeter to determine where the problem is.

    At the moment I only have the amp function on a low-end multimeter that has a 250mA limit. This is obviously insufficient. Please suggest a usable meter for this task, or perhaps suggest where the fault might lie.

    I can of course recap the whole thing, but I'd like to think that will fix it before starting out on this.

    This PSU has a 20-pin connector, but claims 19A on the 12V rail. So it should be possible to wire up a 4-pin connector to get a 20+4 connector to support newer motherboards.

    Feel free to correct my understanding ofr offer any suggestions. All help appreciated.
    Tags: None
    • goodpsusearch
      Badcaps Legend
      • Oct 2009
      • 2850
      • Greece
      #2
      Re: ATX PSU Testing

      Post some photos of the internals...

        Comment

        • mariushm
          Badcaps Legend
          • May 2011
          • 3799
          #3
          Re: ATX PSU Testing

          Check the voltages on the 5v and 12v while the system powers up.
          If they dip too low, you might have a problem there.

          The floppies are 5v if I remember correctly, so if you shorted the 5v you may have broken a capacitor inside that's now making the psu give too low voltage on 5v

          Open it up and post pictures, sometimes the fault is visible.

          As for 19A on 12v, I doubt it... that would mean 230 watts out of 350 watts usable on 12v - unless it's a relatively new psu with modern design, that rating is a lie. Generally old 350w psus have about 12-14A on 12v

            Comment

            • bigbeark
              Badcaps Veteran
              • Jan 2010
              • 661
              • Canada
              #4
              Re: ATX PSU Testing

              Here are the pictures. The yellow wire of the floppy connector started smoking, you can see the burnt wire in pic#6.

              There are NO fuyuhu caps in there, which is probably why these Dynex PSUs are quite reliable. There is no burn damage inside the PSU.

              Please let me have your comments.
              Attached Files

                Comment

                • mariushm
                  Badcaps Legend
                  • May 2011
                  • 3799
                  #5
                  Re: ATX PSU Testing

                  Yeah... E131865 , made by Huntkey

                  Probably one of the models here : http://www.huntkey.com/Product/Producttype.aspx?id=42

                  A very similar board and power supply is reviewed here: http://www.hardwaresecrets.com/artic...y-Review/527/1

                  This one was rated for 450 watts but only made it to 357 watts, so I wouldn't be surprised if yours is a bit overrated.

                  I don't see anything obviously bad, so check the voltages when you power the power supply.

                    Comment

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