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Burned tantalum caps in old Agfa Scanner

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    #1

    Burned tantalum caps in old Agfa Scanner

    Hi, when turning on my Agfa StudioScan II (manufactured around mid 90s)
    which has been unused for several years, there was smoke coming out from the vents
    (smelling like new electronics ). I open it up and I see these two tantalum
    bead caps with burn marks.

    The caps read 22-16 and ++② (number 2 in a circle). Does anyone know what the
    number 2 in the circle means?
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    #2
    Re: Burned tantalum caps in old Agfa Scanner

    Those are 22uF 16V tantalum dipped capacitors. They can last for decades - but if they get overvoltage or negative voltage, they will short out. Or if the big electrolytic capacitors are bad, the high ripple current roasts the tantalums. Check the power supply voltage too. I don't think the ② is important.

    Comment

      #3
      Re: Burned tantalum caps in old Agfa Scanner

      The "2" in a circle is the manufacturer's logo. The mfr was Sprague.
      PeteS in CA

      Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
      ****************************
      To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
      ****************************

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        #4
        Re: Burned tantalum caps in old Agfa Scanner

        Originally posted by PeteS in CA View Post
        The "2" in a circle is the manufacturer's logo. The mfr was Sprague.
        Thank you. That gives me some confidence when finding
        replacement parts.

        Originally posted by redwire View Post
        Those are 22uF 16V tantalum dipped capacitors. They can last for decades - but if they get overvoltage or negative voltage, they will short out. Or if the big electrolytic capacitors are bad, the high ripple current roasts the tantalums. Check the power supply voltage too. I don't think the ② is important.
        From what I've read tantalum caps are not very reliable.
        My incident matches this article (fail when turning on after
        having been unpowered for a long time).
        http://minuszerodegrees.net/failure.htm
        Anyway, I plan to check the voltage and recap as many as I can.

        Cheers!

        Comment

          #5
          Re: Burned tantalum caps in old Agfa Scanner

          Hi, would like to report back that it works fine now. I replaced all the 22uF 16V's with SMD style caps
          which happened to be available locally and left the 10uF 16V ones and others untouched since they
          all looked OK (and I hope they are OK). Cheers.
          Attached Files

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