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    #1

    PSU works, but connected to motherboard does not

    I have an problematic 500W psu and problem is that when I test PSU on the table, nothing connected, it is working and giving all proper voltage ( 3,3, 5 and 12 V )
    But, when I connect it to motherboard, computer wont start, the PSU wont start either ( fan is not revolving )
    Motherboard is MSI with H66 chipset, Celeron G1610 and 2 GB DDR3, nothing else
    When I disconnect 4 pin motherboard connector, PSU starts to work, but computer, that is normal, doesnt
    I also tested with an older computer, P3 on 800 Mhz, CD and hard drive, and PSU worked well, just for testing I installed Windows XP and works well
    I concluded that PSU works but if motherboard needs more watts, PSU fails
    Question is : which PSU component is responsiblle to give proper voltage under heavy load ?

    Thanks in advance
    Tags: None
    #2
    Re: PSU works, but connected to motherboard does not

    The motherboard could be faulty also. Have you tried it with a known good psu ? Also, which is the brand / model of the psu ? Pics ?

    Comment

      #3
      Re: PSU works, but connected to motherboard does not

      Motherboard is not faulty, I tried another PSU, and works well, and the brand is Blueberry 500w

      Comment

        #4
        Re: PSU works, but connected to motherboard does not

        Model and inside pics, please.

        Comment

          #5
          Re: PSU works, but connected to motherboard does not

          What is the Part Number of the controller IC ?

          Comment

            #6
            Re: PSU works, but connected to motherboard does not

            First I have to apologize that I gave You wrong brand name.
            It is not Blueberry 500W ( I mixed up this PSU and Blueberry 500 W PSU, which is not working at all - doesnt have burned parts, just fuse burnes, when I replace fuse, it burnes again )

            This problematic psu has no name, and I think, it is custom ordered PSU.
            Images are attached and You can also see part number of controller IC.
            Last edited by ciki022; 11-06-2013, 11:08 AM.

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              #7
              Re: PSU works, but connected to motherboard does not

              First I have to apologize that I gave You wrong brand name.
              It is not Blueberry 500W ( I mixed up this PSU and Blueberry 500 W PSU, which is not working at all - doesnt have burned parts, just fuse burnes, when I replace fuse, it burnes again )

              This problematic psu has no name, and I think, it is custom ordered PSU.
              Images are attached and You can also see part number of controller IC.
              Attached Files

              Comment

                #8
                Re: PSU works, but connected to motherboard does not

                Originally posted by ciki022 View Post
                First I have to apologize that I gave You wrong brand name.
                It is not Blueberry 500W ( I mixed up this PSU and Blueberry 500 W PSU, which is not working at all - doesnt have burned parts, just fuse burnes, when I replace fuse, it burnes again )

                This problematic psu has no name, and I think, it is custom ordered PSU.
                Images are attached and You can also see part number of controller IC.
                Instead of "custom ordered", I would venture "crap ordered". Wel, the others may expain better than me, but it seems to be an old design, suited for P3s, early p4s, AMD Athlon XPs, etc. From the looks of it, something about 200 to 250W tops.

                As you say it worked ok in a P3, and didn´t power in the MSI, I believe it is just a case of psu not being able ( by design ) to supply the necessary currents for the motherboard ( you didn´t state the exact model of MSI motherboard, but I suppose it is for some fairly recent cpu ( core quads, i3, i5, etc... )

                Basically, I would suggest you to install it in the p3 machine, and find a good , reputable brand for the newer machine.

                Comment

                  #9
                  Re: PSU works, but connected to motherboard does not

                  Yes, this PSU is old, built in 2007 ( see first image )
                  But, last three years this PSU powered Athlon 3000+ on AM2 motherboard, with 2 GB ram and one hard drive and one DVDRW drive, without any problems
                  Because of that fact, I think this PSU is not suited just for P3, early P4, Athlon XPs, like You wrote, but it can power some modern systems
                  I think that problem is in one/some psu component/s that are failing under heavy load, like I wrote in first post, I just dont know which one/s
                  Last edited by ciki022; 11-06-2013, 12:40 PM.

                  Comment

                    #10
                    Re: PSU works, but connected to motherboard does not

                    170-200W max

                    Comment

                      #11
                      Re: PSU works, but connected to motherboard does not

                      It is suited for weak things. With due respect, an Athlon 3000+ ( runs at 2.5 - 2.7Mhz, if I remember right ) is not a modern system.
                      And it has a weak 12V current rating. Considering the age of the thing, and some lies from the manufacturer in the label, we could stipulate that it is able to give about 10A in the 12V line. That would be too weak for most modern systems.

                      By the way, post the correct model of MSI motherboard and cpu.

                      Comment

                        #12
                        Re: PSU works, but connected to motherboard does not

                        This thing lacks a proper input filter and has 330uF input caps. It i definitely a bad psu.

                        Comment

                          #13
                          Re: PSU works, but connected to motherboard does not

                          OK! Here we go ....... As you said when you are connecting 4 Pin Connectors that means +12V connector, then it is Load failing . I think, most probably +12V Diode bracket's one side is open . A diode bracket is consists of two diodes . One of the two diodes may be open . This is why +12V Diode bracket is failing to supply adequate Power when you are connecting 4 Pin Connector . Firstly Check that +12V Diode Bracket very carefully by removing from the PCB and be sure - Is it's one side is open or not . Then give a quick check to other +5V and +3.3V Brackets also .

                          If you found all outputs Diode Brackets are OK, then do this second job . In the controller section you have B494 Controller IC . If all outputs Diode Brackets are OK, then you have to change this B494 IC . You can use DB494/TL494/UV494/UVX494 anyone of these . You can use KA7500/KA7500B in substitute of B494 . Because TL494 and KA7500 are same .

                          Both steps Images are attached below . And show us what is the result ......
                          Attached Files

                          Comment

                            #14
                            Re: PSU works, but connected to motherboard does not

                            when plugged to MB, please check the voltages on the big connector if you can access them from the cable side. Any voltages low?? Continuity between PS_on and GND?

                            Did you try to put some load on in while it is "on the table" ?

                            Comment

                              #15
                              Re: PSU works, but connected to motherboard does not

                              Escort Eagle,
                              thanks for the tips, I will try later, at the moment I am at work

                              domas
                              I will also try what You suggested
                              And what kind of "heavy load" I can connect "on the table" ( I tried with two fans and one hard disk, and it was working, but that isnt "heavy load" ) ?

                              Comment

                                #16
                                Re: PSU works, but connected to motherboard does not

                                no, i would say something like 5 amps, some 2 ohm resistor, but it has to be high wattage else it would overheat instantly

                                Comment

                                  #17
                                  Re: PSU works, but connected to motherboard does not

                                  or a 55++W automotive light bulb

                                  Comment

                                    #18
                                    Re: PSU works, but connected to motherboard does not

                                    Originally posted by Escort Eagle View Post
                                    In the controller section you have B494 Controller IC . If all outputs Diode Brackets are OK, then you have to change this B494 IC . You can use DB494/TL494/UV494/UVX494 anyone of these . You can use KA7500/KA7500B in substitute of B494 . Because TL494 and KA7500 are same
                                    In addition to the above: the other IC is a LM339. The combination TL494/LM339 was widely used in AT PSU's. They each cost just peanuts.

                                    re-atari

                                    Comment

                                      #19
                                      Re: PSU works, but connected to motherboard does not

                                      ...and in many ATX as well

                                      Comment

                                        #20
                                        Re: PSU works, but connected to motherboard does not

                                        you may remove the transformer to checks that secondary heatsinked diode, it is always more easy than trying test it in circuit may give unaccurate reading.

                                        but it depends on you to remove the diode heatsinked by Escort suggested or removing the transformer. just make it easy for you. i have that PSU too. if im not recall wrong, the brand model is Eyota. crap cheap PSU.. but I think it could be to powering above P4 CPU, i have tested it on my cpu before and it has no problem.

                                        Lack of input filtering makes me afraid for my motherboard safety
                                        "There is no shortcut to be successful. No pain, no gain."

                                        Best Regards
                                        Rudi
                                        Thank You

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