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What's worse than 2 transistor SB? 2 transistor with transil

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    What's worse than 2 transistor SB? 2 transistor with transil

    I got this Chieftec half-sized ATX PSU (don't know the model right now, but it is ATX sized, just shorter) that is smells and does not turn on.

    It is a single transistor forward with 2 transistor stand-by. One cap bad at +5 V SB, OK replaced both. Than there was some diode burned, seemed like a -12 V eh? Replaced with more fat shottky. Wrong. It whistles and there is 16 V at +5 V SB!! It was 6.8V transil which was there to bring the voltage down. No wonder it was completelly baked and blown after those years. And it makes reason there was 16V cap after the stand-by rectifying diode and not sooner than in the end there was 10V, just next to the transil.

    I will probably replace it with 6V transil but in bigger package, DO201 and for 1500W spikes. And replace the caps with 16V/1000uF KZHs. Also thinking about maybe relocating the transil a bit as it is under coil for passive PFC without much cooling possibilities.
    Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

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    #2
    Re: What's worse than 2 transistor SB? 2 transistor with transil

    ^
    The problem is more likely that one of the small 50V caps has failed. give it a complete recap (with the exception of the two primary caps) and it will probably be fine. The transil is only there so that the failed cap doesn't cause the "16VSB rail" and cook the motherboard. In your case, though, it looks like it melted when presented with an over-voltage condition rather than doing its job. Normally, they will just and blow up the transistor, but the motherboard should survive.
    Last edited by c_hegge; 08-20-2014, 07:28 PM.
    I love putting bad caps and flat batteries in fire and watching them explode!!

    No wonder it doesn't work! You installed the jumper wires backwards

    Main PC: Core i7 3770K 3.5GHz, Gigabyte GA-Z77M-D3H-MVP, 8GB Kingston HyperX DDR3 1600, 240GB Intel 335 Series SSD, 750GB WD HDD, Sony Optiarc DVD RW, Palit nVidia GTX660 Ti, CoolerMaster N200 Case, Delta DPS-600MB 600W PSU, Hauppauge TV Tuner, Windows 7 Home Premium

    Office PC: HP ProLiant ML150 G3, 2x Xeon E5335 2GHz, 4GB DDR2 RAM, 120GB Intel 530 SSD, 2x 250GB HDD, 2x 450GB 15K SAS HDD in RAID 1, 1x 2TB HDD, nVidia 8400GS, Delta DPS-650BB 650W PSU, Windows 7 Pro

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      #3
      Re: What's worse than 2 transistor SB? 2 transistor with transil

      There are only tiny caps, 0,22 and 0,47 uF, they seemed fine measured in circuit. Than some 10uF caps, they were also more or less in spec, that's the thing. But I will replace them for sure and test out of circuit…
      Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

      Exclusive caps, meters and more!
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        #4
        Re: What's worse than 2 transistor SB? 2 transistor with transil

        It could be one of the 10uF caps.
        I love putting bad caps and flat batteries in fire and watching them explode!!

        No wonder it doesn't work! You installed the jumper wires backwards

        Main PC: Core i7 3770K 3.5GHz, Gigabyte GA-Z77M-D3H-MVP, 8GB Kingston HyperX DDR3 1600, 240GB Intel 335 Series SSD, 750GB WD HDD, Sony Optiarc DVD RW, Palit nVidia GTX660 Ti, CoolerMaster N200 Case, Delta DPS-600MB 600W PSU, Hauppauge TV Tuner, Windows 7 Home Premium

        Office PC: HP ProLiant ML150 G3, 2x Xeon E5335 2GHz, 4GB DDR2 RAM, 120GB Intel 530 SSD, 2x 250GB HDD, 2x 450GB 15K SAS HDD in RAID 1, 1x 2TB HDD, nVidia 8400GS, Delta DPS-650BB 650W PSU, Windows 7 Pro

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          #5
          Re: What's worse than 2 transistor SB? 2 transistor with transil

          Neither of them. There were yet another two small caps, one of them, a 47uF one, measured 0,02 uF. ESR was out of range
          Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

          Exclusive caps, meters and more!
          Hardware Insights - power supply reviews and more!

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            #6
            Re: What's worse than 2 transistor SB? 2 transistor with transil

            pics?
            Things I've fixed: anything from semis to crappy Chinese $2 radios, and now an IoT Dildo....

            "Dude, this is Wyoming, i hopped on and sent 'er. No fucking around." -- Me

            Excuse me while i do something dangerous


            You must have a sad, sad boring life if you hate on people harmlessly enjoying life with an animal costume.

            Sometimes you need to break shit to fix it.... Thats why my lawnmower doesn't have a deadman switch or engine brake anymore

            Follow the white rabbit.

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              #7
              Re: What's worse than 2 transistor SB? 2 transistor with transil

              It's a Chieftec SI-A300P3, found some pics and info here http://www.vseprosto.net/2012/09/chi...rnogo-rezhima/
              Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

              Exclusive caps, meters and more!
              Hardware Insights - power supply reviews and more!

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