Cap reformation question

[Joe R.]

At 08:37 PM 12/6/05 -0700, you wrote:
>Joe R. wrote:
>
>>    Q: How high of a voltage do you use the reform the caps?  I'm wondering
>>if it's necessary to apply full (or nearly full) rated voltage or if
>>they're fully reformed at say 5 VDC. Has anybody done any testing in this
>>area?
>>  
>>
>I assume the vorking voltage + some safety margin.

   I disagree. Caps have a definite voltage limit and in many of them it's
not much more than the stated working voltage. If you apply too high a
voltage then the insulating layer will breakdown and the cap will short.
Limiting the current will prevent the cap from exploding but I think you'll
permanetly damage the cap.  I wouldn't go go above what ever the maximum
voltage is for the cap.  But further, I wonder if even that much voltage is
necessary. I believe that once you apply a certain voltage the insulating
layer reforms and any higher voltage is unnecessary and possibly dangerous
to the cap.


>A quick search found this link on the web of a circuit to reform the caps.
>http://www.vmars.org.uk/capacitor_reforming.htm
>

   Interesting circuit but it's really only good for caps that are rated
between the ignition and maximum voltages of the neon lamp. Most of the
circuits that we're interested in will be 5 or 12VDC and that too low for
the neon lamp to trigger (~60V).  That's the problem with this whole
subject, there's no one approach that's going to satisfy EVERY situation.

   Joe