unused yet old caps...

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  • El-kamote
    Member
    • Jul 2006
    • 12
    #1

    unused yet old caps...

    it's been a long time since my last post

    anyway, i purchased a lot of old stocks of unused caps from a flea market, a mix of nichicon PLs and panasonic HFQs of different values, with date codes around 1999 or 2000. i'm planning to use these on several old boards that needed recapping. do you guys recommend using these, even after reconditioning these little gems?
    Tags: None
    • stevo1210
      Badcaps Legend
      • Oct 2006
      • 4156
      • Australia
      #2
      Re: unused yet old caps...

      I don't see a problem to why you wouldn't use them. They haven't been used before. Caps can withstand temperatures from -55 to 105c and I doubt anyone would put them in any environment higher or lower than specified so I don't think there is any problem with them. You could do an ESR check if you are curious about thier quality.
      Don't find love, let love find you. That's why its called falling in love, because you don't force yourself to fall, you just fall. - Anonymous

        Comment

        • PCBONEZ
          Grumpy Old Fart
          • Aug 2005
          • 10661
          • USA
          #3
          Re: unused yet old caps...

          The aluminum oxide layer breaks down over time.
          [The reason they have a shelf life.]
          If it's shot an inrush of current may blow the caps. (Or something else.)

          You may need to perform a process called "reforming" which restores the layer.
          - I have not done it myself yet, only read on it a few times.

          Basic idea is to apply low DC volts and gradually raise it to a bit over the caps volt rating. - You can use google too, but please talk to a member here that's actually done it. I know there's one or two that have because I've seen it discussed.

          .
          Mann-Made Global Warming.
          - We should be more concerned about the Intellectual Climate.
          -
          Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
          - Dr Seuss
          -
          You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
          -

            Comment

            • i4004
              Badcaps Legend
              • Oct 2006
              • 2029
              #4
              Re: unused yet old caps...

              http://www.chemi-con.com/guide/pg10.php

              3. Capacitors that have been stored for long periods of time may have high leakage current due to deterioration of the dielectric. When these capacitors are installed into a circuit and charged for the first time, a large amount of current will flow into the capacitors to reform the oxide layers and may blow a fuse. Therefore, it is advisable to reform the capacitors by applying voltage through a resistor of approximately 1k(omega) before use. See footnotes.




              --------------------------------------------------------------------------------
              Footnotes:
              1. Voltage Reforming: Apply the full rated voltage to the capacitors through a resistor of approximately 1k(omega) for approximately 30 minutes.

                Comment

                • kc8adu
                  Super Moderator
                  • Nov 2003
                  • 8832
                  • U.S.A!
                  #5
                  Re: unused yet old caps...

                  i reform lytics in vintage gear by bringing the unit up slowly with a variac.
                  i have never had any problems with low esr lytics for mobo's even some i have that are 5 years old.
                  i suspect the quality/purity of the foil determines how well they hold their "form"

                    Comment

                    • El-kamote
                      Member
                      • Jul 2006
                      • 12
                      #6
                      Re: unused yet old caps...

                      Yeah, I read it in most datasheets before that caps stored for long periods must be "reformed" before being applied in circuits (in Panasonic datasheets it's called "capacitor reconditioning.") Basically charging it with a 1k current-limiting resistor attached in series with voltages close to spec at 30 minutes minimum.

                      I hope these unused caps will hold, notwithstanding these were stuck in shelves for a long time. 50 pieces of low-ESR Pana HFQ caps for less than a dollar is too good to pass up

                      Thanks for the advice.

                        Comment

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