Re: Electrolytic caps?

From: Pooh Bear (rabbitsfriendsandrelations_at_hotmail.com)
Date: 02/28/05 

Date: Mon, 28 Feb 2005 00:10:49 +0000

mc wrote:

> "Tim Wescott" <tim@wescottnospamdesign.com> wrote in message
> news:1121vm3s9fi6a0b@corp.supernews.com...
>
> > Its "forming" (technically "reforming" since it was already done once at
> > the factory long long ago). You can do a web search on electrolytic
> > forming.
> >
> > Basically you feed it rated voltage through a big current limiting
> > resistor -- what you're doing is restoring the aluminum oxide layer on the
> > foil. There are a number of techniques for verifying that the forming is
> > complete (vs. the cap being bad) -- basically when you think you're done
> > you test with more than the rated voltage to see if the thing leaks -- if
> > so, you scrap it.
> >
> > I've never done it, but it's a common thing with tube-equipped boat
> > anchors.
>
> The way I do it, which I thought was standard, was to gradually raise the
> voltage from zero over a period of minutes, monitoring for leakage all the
> time, and then leave it charged to the rated voltage for some time.

I wouldn't call that the standard method but ramping the voltage sounds like a
nice idea. You still want to use a current limiting resistor though.

You also need to apply the rated voltage for some time IIRC to ensure that the
oxide film is fully reformed.

> You can measure quite an increase in capacitance from doing this, even if
> the capacitor didn't test out as defective to begin with.

 As compared to the rated capacitance ?

Graham

Relevant Pages

  • Re: Electrolytic caps?
    ... There are a number of techniques for verifying that the forming is ... and then leave it charged to the rated voltage for some time. ... I wouldn't call that the standard method but ramping the voltage sounds like a ... As compared to the rated capacitance? ...
    (sci.electronics.equipment)
  • Re: Electrolytic caps?
    ... There are a number of techniques for verifying that the forming is ... and then leave it charged to the rated voltage for some time. ... I wouldn't call that the standard method but ramping the voltage sounds like a ... As compared to the rated capacitance? ...
    (sci.electronics.design)
  • Re: Electrolytic caps?
    ... There are a number of techniques for verifying that the forming is ... and then leave it charged to the rated voltage for some time. ... I wouldn't call that the standard method but ramping the voltage sounds like a ... As compared to the rated capacitance? ...
    (sci.electronics.components)
  • Re: Electrolytic caps?
    ... You can do a web search on electrolytic ... There are a number of techniques for verifying that the forming is ... and then leave it charged to the rated voltage for some time. ... You can measure quite an increase in capacitance from doing this, ...
    (sci.electronics.equipment)
  • Re: Electrolytic caps?
    ... You can do a web search on electrolytic ... There are a number of techniques for verifying that the forming is ... and then leave it charged to the rated voltage for some time. ... You can measure quite an increase in capacitance from doing this, ...
    (sci.electronics.design)