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Hp smps power suppy ps4321 help!!!!!!

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    Hp smps power suppy ps4321 help!!!!!!

    Dear all

    i have several power supplies that when the transformer is connected on board
    secondary pins are all shorted (7pins).
    by removing it pins 1 and 5 are shown short and 2,3,4,6,7 are shorted between them.

    i tried to find datasheet but nothing. ps is manufactured by LITEON

    CAN ANYONE HELP!

    THANKS.

    ON PS I HAVE 4.3V ON POWER SWITCH ON
    Attached Files

    #2
    Re: Hp smps power suppy ps4321 help!!!!!!

    It is a high frequency transformer, you can't ohm measure it.
    You need to use a transformer tester like a ring test, can also be done with an Oscilloscope if you Google for it.
    "The one who says it cannot be done should never interrupt the one who is doing it."

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      #3
      Re: Hp smps power suppy ps4321 help!!!!!!

      Sometimes a ring tester does not always read the winding correctly if there not very many turns on a winding I have run into this type of issue I have seen where the two red LEDs are light or in the yellow and the transformer is still working
      9 PC LCD Monitor
      6 LCD Flat Screen TV
      30 Desk Top Switching Power Supply
      10 Battery Charger Switching Power Supply for Power Tool
      6 18v Lithium Battery Power Boards for Tool Battery Packs
      1 XBox 360 Switching Power Supply and M Board
      25 Servo Drives 220/460 3 Phase
      6 De-soldering Station Switching Power Supply 1 Power Supply
      1 Dell Mother Board
      15 Computer Power Supply
      1 HP Printer Supply & Control Board * lighting finished it *


      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
      2 Hem Saw Computer Stack Board

      All of these had CAPs POOF
      All of the mosfet that are taken out by bad caps

      Comment


        #4
        Re: Hp smps power suppy ps4321 help!!!!!!

        Thanks for your message.

        i have noticed when transformer is installed on board and leave it rest for some time without power i get a very small resistance which means is not short but power supply has 4.3-4.5v stb voltage and is not turning on.
        there is PS25A and TL594 ic on secondary side which are not short.

        i checked all diodes and capacitors and non of them seem to be short.

        there is a transistor near the 3 optocouplers on which i get the 2.45v
        on the optocouplers on secondary side first one reads 0v and the other 2 read 10.8 to 11.5v.
        i removed optocoupler primary side and i placed diode instead to see if there is getting something HOT but nothing.

        do you have any ideas.

        Thanks
        Last edited by NConstantinou; 04-30-2022, 12:43 AM.

        Comment


          #5
          Re: Hp smps power suppy ps4321 help!!!!!!

          Change out the caps for the 5VSB rail.

          Comment


            #6
            Re: Hp smps power suppy ps4321 help!!!!!!

            The 5vsb and 12v ca0s have been replaced

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