Burning smell from PSU but no visible problems!

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  • Tom41
    Badcaps Veteran
    • Oct 2005
    • 336
    • England

    #1

    Burning smell from PSU but no visible problems!

    This evening I went into my computer room to find a strong 'burning plastic' smell. After shutting down my secondary PC (which I'd left on to share the Internet using the Nintendo Wifi USB connector), I had a sniff around and found what I believe to be the source of the smell, the PSU on my secondary PC.

    I opened up the PC to check for any visible signs of damage. There is nothing on the motherboard or any other device that looks burnt, and all the capacitors (Rubycon!) are nice and flat-topped. All vents on the PC and PSU were clear, not blocked by anything and relatively free of dust.

    I also opened up the PSU. Again, there's nothing visibly wrong - no charring, burning or melting was visible. The capacitors are all Samxon, and show no signs of bulging.
    Then again, it did only have one input capacitor and wimpy heatsinks, but this PSU has served me well for a long time. The PC is not showing any bad cap symptoms yet (random reboots, POST errors and such), but I dare not keep it switched on for extended periods of time any more.

    One thing I did notice - when I opened up the PSU, a tiny metal fragment fell out, that looked rather like an end of component lead with a bit of solder on the end. Could a component have come loose and started arcing? Surely there would be some physical evidence if that were the case, though...

    This particular PC gets much less use than the other one in the computer room, so it's also possible that dust settled inside the PSU and made the smell when the heatsinks got hot. What do you guys think?
    You know there's something wrong when you open your PC and it has vented Rubycons...
  • 370forlife
    Large Marge
    • Aug 2008
    • 3112
    • United States

    #2
    Re: Burning smell from PSU but no visible problems!

    Remove the pcb from the psu case and check for bad solder joints. Clean all the dust out.

    Samxon...single input cap, sounds like a APFC CWT unit (if the samxon is from the factory)

    Comment

    • stj
      Great Sage 齊天大聖
      • Dec 2009
      • 31003
      • Albion

      #3
      Re: Burning smell from PSU but no visible problems!

      use your nose to find the source of burning.

      Comment

      • Tom41
        Badcaps Veteran
        • Oct 2005
        • 336
        • England

        #4
        Re: Burning smell from PSU but no visible problems!

        Today I finally found the source of the burning smell - inside the PSU, as I feared. The PSU is a Jean Tech, 350W.

        Upon closer inspection, I found that one of the coils inside felt very loose to the touch, and the glue between it and the input capacitor had broken. I'm guessing the coil developed a 'hot spot', melting the glue and causing it to move out of place, touching another heat sink. The smell was definitely coming from the vicinity of the coil.

        I've attached two photos of the coil and capacitor - what do you guys think? Perhaps the combined heat from the hot spot and the heat sink caused the 'paper' on the coil to start making a smell?
        Attached Files
        You know there's something wrong when you open your PC and it has vented Rubycons...

        Comment

        • Agent24
          I see dead caps
          • Oct 2007
          • 4951
          • New Zealand

          #5
          Re: Burning smell from PSU but no visible problems!

          Shorted coil or something else short causing high current through it?
          "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
          -David VanHorn

          Comment

          • smalltownguy
            Senior Member
            • Feb 2010
            • 127
            • US

            #6
            Re: Burning smell from PSU but no visible problems!

            Originally posted by Tom41
            Today I finally found the source of the burning smell - inside the PSU, as I feared. The PSU is a Jean Tech, 350W.

            Upon closer inspection, I found that one of the coils inside felt very loose to the touch, and the glue between it and the input capacitor had broken. I'm guessing the coil developed a 'hot spot', melting the glue and causing it to move out of place, touching another heat sink. The smell was definitely coming from the vicinity of the coil.

            I've attached two photos of the coil and capacitor - what do you guys think? Perhaps the combined heat from the hot spot and the heat sink caused the 'paper' on the coil to start making a smell?
            What's the name of that coil? I've got another power supply with the same symptoms. There's charring on that coil. I'll replace it, if I can find a cheap replacement.

            Comment

            • Stefan Payne
              Badcaps Legend
              • Dec 2009
              • 1267
              • Germany

              #7
              Re: Burning smell from PSU but no visible problems!

              Originally posted by Agent24
              Shorted coil or something else short causing high current through it?
              or just a faulty coil...

              Comment

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