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ATX PSU SL-500 Short circuit can't find where? Transformer?

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    ATX PSU SL-500 Short circuit can't find where? Transformer?

    Hello,

    I got ATX PSU SL-500 PSU. Images Attached.
    It has blown VIPER22A, that I replaced.
    Connected trough light bulb the bulb glows very bright indicating a short.

    I tested every component on hot side of PCB and can't find the short circuit.
    However the problem goes away removing +5VSB transformer.

    The winding in questions of +5VSB transormer shows 0.08Ohms, is this normal?
    Attached Files

    #2
    Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

    If you are reading 0.08Ω DC resistance on the primary winding I would say the transformer is shorted.
    A normal primary side winding resistance should be around 2Ω to 5Ω
    Secondary resistance would be normal at around 0.05Ω to 0.10Ω

    Here two examples:
    https://www.badcaps.net/forum/showpo...5&postcount=18
    https://www.badcaps.net/forum/showpo...8&postcount=60

    And here is a datasheet for a transformer that should have similar ratings, pinout may be wrong but you can see the DC resistance values:
    https://cdn.badcaps-static.com/pdfs/...5308f3be00.pdf
    From: https://www.we-online.com/catalog/en/MID-OLSTM
    "The one who says it cannot be done should never interrupt the one who is doing it."

    Comment


      #3
      Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

      a ring tester or component tester that has the inductance software would be handy

      Comment


        #4
        Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

        Thanks for suggestions, I ordered IC BH0270A, maybe it will fix it. Also looking for replacement transformer to salvage from another PSU, but so far can't find it.

        Comment


          #5
          Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

          Originally posted by smile View Post
          Thanks for suggestions, I ordered IC BH0270A, maybe it will fix it.
          If the lamp is bright when the power supply is soft off this will not fix it.
          Because the primary power supply should be off in that case, only the Viper providing 5Vsb...

          But of course if the MOSFET inside the FSBH0270ANY PWM chip has failed shorted maybe that is what you where reading.
          But the two transformers should be completely isolated.
          And removing the 5Vsb transformer in that case would not remove the short...

          Do you have a "component tester" also called "transistor tester" or a ring tester to check the transformer with?
          "The one who says it cannot be done should never interrupt the one who is doing it."

          Comment


            #6
            Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

            Originally posted by Per Hansson View Post
            If the lamp is bright when the power supply is soft off this will not fix it.
            Because the primary power supply should be off in that case, only the Viper providing 5Vsb...

            But of course if the MOSFET inside the FSBH0270ANY PWM chip has failed shorted maybe that is what you where reading.
            But the two transformers should be completely isolated.
            And removing the 5Vsb transformer in that case would not remove the short...

            Do you have a "component tester" also called "transistor tester" or a ring tester to check the transformer with?
            Well replaced the transformer for +5VSB that is for sure not 0.08ohm resistance, but the result is the same short circuit bulb shines bright. Still waiting for PWM IC.

            "Do you have a "component tester" " - Have ESR meter, miliohm meter 2 wire, inductance meter, PEAK Atlas Atlas DCA Pro.

            Comment


              #7
              Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

              Well since you have a inductance meter why don't you use it?
              "The one who says it cannot be done should never interrupt the one who is doing it."

              Comment


                #8
                Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                Originally posted by Per Hansson View Post
                Well since you have a inductance meter why don't you use it?
                Maybe because I don't know what it should show as good/bad ?
                The resistance is very low so what is normal values?

                Comment


                  #9
                  Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                  Here is an example from a Seasonic SS-250FS with a VEE19FRC3 5VSB Transformer:
                  Primary:
                  3.44ohm
                  1.85mH
                  444kHz
                  Q=9.2

                  Aux:
                  0.24ohm
                  0.06mH
                  736kHz
                  Q=17.8

                  Secondary:
                  0.01ohm
                  2.49µH
                  750kHz
                  Q=20.6

                  Values taken with a "component tester" so nothing fancy, but still the relative values should tell something.
                  "The one who says it cannot be done should never interrupt the one who is doing it."

                  Comment


                    #10
                    Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                    Primary:
                    2.66ohm
                    1.89mH

                    Aux:
                    0.48ohm
                    150mH

                    Secondary:
                    0.30ohm
                    108µH

                    Comment


                      #11
                      Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                      Originally posted by Per Hansson View Post
                      Here is an example from a Seasonic SS-250FS with a VEE19FRC3 5VSB Transformer:
                      Primary:
                      3.44ohm
                      1.85mH
                      444kHz
                      Q=9.2

                      Aux:
                      0.24ohm
                      0.06mH
                      736kHz
                      Q=17.8

                      Secondary:
                      0.01ohm
                      2.49µH
                      750kHz
                      Q=20.6

                      Values taken with a "component tester" so nothing fancy, but still the relative values should tell something.
                      I have a question for you that is related but with a different type of tester using a blue capacitor tester and you get a 0.00 value dose this mean that this winding might be shorted because I have used it in the past with a ring tester to find possible shorted windings with this but do not know how accurate this type of testing does because I have had a switching transformer show very low or no light on the tester which is supposedly means that the winding is shorted but the device works correctly with this transformer testing this way sometimes which I have not totally understand the results of the tester

                      If a component tester does a better job telling you that a switching transformer is shorted can you please send me a link to where I can buy one that does a better job doing this type of testing

                      Thanks
                      Last edited by sam_sam_sam; 08-05-2022, 08:47 AM.
                      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


                        #12
                        Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                        Originally posted by smile View Post
                        Primary:
                        2.66ohm
                        1.89mH

                        Aux:
                        0.48ohm
                        150mH

                        Secondary:
                        0.30ohm
                        108µH
                        Ok, in these readings you no longer are close to a dead short on the primary winding so something in your testing must have changed?
                        For another example here is a new transformer I bought by mistake related to this thread.


                        Würth Elektronik MID-OLON Offline Flyback Transformer article number: 750312279
                        Product page: https://www.we-online.com/catalog/en/MID-OLON#750312279
                        Datasheet: https://cdn.badcaps-static.com/pdfs/...dc18d6f15f.pdf

                        Note:
                        1 > 9 is Primary
                        3 > 8 is Aux
                        5 > 6 is Secondary

                        Code:
                        DC Resistance	Inductance & Q Factor				Inductance & Q Factor
                        UNI-T UT61E:	Agilent U1733C:					GM328R "Component Tester":
                        1 > 9 = 0.50Ω	730µH	100khz=Q300 10khz=Q75 1khz=Q8.0	760µH 840kHz  Q=5.0
                        3 > 8 = 0.08Ω	13.3µH	100khz=Q200 10khz=Q7.9 1khz=Q0.8	0.24µH 2424kHz Q=18.4
                        5 > 6 = 0.01Ω	2.1µH	100khz=Q100 10khz=Q2.8 1khz=Q0.3	0.22µH 2535kHz Q=5.2


                        Originally posted by sam_sam_sam View Post
                        I have a question for you that is related but with a different type of tester using a blue capacitor tester and you get a 0.00 value dose this mean that this winding might be shorted because I have used it in the past with a ring tester to find possible shorted windings with this but do not know how accurate this type of testing does because I have had a switching transformer show very low or no light on the tester which is supposedly means that the winding is shorted but the device works correctly with this transformer testing this way sometimes which I have not totally understand the results of the tester

                        If a component tester does a better job telling you that a switching transformer is shorted can you please send me a link to where I can buy one that does a better job doing this type of testing

                        Thanks
                        To better understand your ring tester please watch this Youtube video linked below.
                        As you can see even one shorted ring causes a very big drop in ring oscillations, of course such a transformer still works, only a bit worse compared to when it was new.
                        It is a good way to test transformers when you don't have access to a datasheet that actually tells you what the values should be, that is its main advantage...
                        If you look at my values in the code box above here you can also see how much it differs from meter to meter: much better to have a meter that gives a more definitive result...
                        P.S: The ring tester is also available as an addon for the component tester if you use the M-firmware from madires that you can build yourself:
                        https://www.youtube.com/watch?v=QBbEYYWiBI8
                        "The one who says it cannot be done should never interrupt the one who is doing it."

                        Comment


                          #13
                          Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                          Well I found similar transformer in another PSU, and repalced it.
                          My meter measures only uH,mH value, and resistance.

                          The readings are in post above.

                          The PSU did not start, in fact the short circuit was still there.
                          I could not find. The VIPER22A was overheating 100deg C.
                          Attached Files
                          Last edited by smile; 08-06-2022, 03:43 PM.

                          Comment


                            #14
                            Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                            Afterwards I decided to see what would blow if I connected direct to mains.
                            This is what blew, magic smoke came from Viper22A, diode next to it.
                            Attached Files

                            Comment


                              #15
                              Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                              I changed the Viper22A and diode from another PSU. The Transformer was also changed (to blue colored one the resistances are not as close to the posted above) as the first one had 1ohm on primary after magic smoke came out from other parts.

                              But after connecting trough the light bulb the thermal camera shows overheating capacitor. Connecting to mains direct makes the cap explode with loud bang
                              Attached Files

                              Comment


                                #16
                                Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                                The transistors on primary side heatsink were desoldered and tested OK.
                                The Viper22A is unknown condition.
                                Diode near viper is OK.
                                All other coponents on primary side are OK with testing using multimeter without desoldering. Any ideas?

                                Comment


                                  #17
                                  Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                                  throw the safety light bulb away and keep blowing everything up first try .

                                  Comment


                                    #18
                                    Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

                                    Originally posted by petehall347 View Post
                                    throw the safety light bulb away and keep blowing everything up first try .
                                    I think you did not read whole thread, all components tested OK that is why I removed the bulb. If I had a variac I would use lower AC voltage to see what heats up. But sometimes it is more easy to let parts explode then to find the problem.

                                    Comment

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