Tech Square

Reforming capacitors

12.73.69.32

Camrahnbay

I have heard this term but do not understand what it means.
When caps sit for a long time dormant ,then charged,what is it that reforms? How long does the reforming take and if a coupling cap,is it going to sound better the more it's used?
What should one know when attempting to reform capacitors?
Thanks,
C.R.B.

Follow Ups:

Google is your friend - 1973shovel 15:29:54 05/30/09 (2)
Reforming applies to electrolytic capacitors. Click on the link below for explanations and "how-to's".

Be careful.
- Lots of information (Open in New Window)
- RE: Google is your friend - Camrahnbay 19:40:07 05/31/09 (1)
  Shovel,
  Thanks for the sight,bookoo info there,all I need really.
  Still got your bike and ride too?
  - RE: "Still got your bike and ride too?" - 1973shovel 19:01:16 06/01/09 (0)
    Sure do. I have two. One I've had for thirty two years now.
    
    Good luck with your caps. I reform them all the time, and they almost always are good, if you do it slowly, and monitor the current.
    
    Good luck, and again, be careful!
RE: Reforming capacitors - Tweekeng 00:26:32 05/23/09 (1)
In my recollection reforming capacitors was only performed on old oil filled electrolytic caps.

I don't remember the exact process but it was something like by applying a high reverse(?) polarity voltage you could reform the layer of aluminum oxide on the plates.

You might ask in the tube asylum.
- RE: Reforming capacitors - unclestu52 13:24:49 05/25/09 (0)
  standard procedure is to apply rated voltage spread slowly over time. Normal recommendation is 5 minutes of ramp up per month in storage. An example would be if you have a capacitor rated at 500 volts and its five years old, you would raise the voltage about 8 volts every five minutes till you reach 500 volts. That's a long time. And you should check for leakage periodically also.
  
  Much easier if you have one of those old Sprague cap testers which allows you to dial in the applied voltage. You can check for leakage as you raise voltage. The military normally throws away caps older than five years, as it takes too much time and monitoring to reform the caps.
  
  Stu

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