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RE: The fallacy of "reforming" capacitors

"Whether or not "reforming" is legitimate or not, can (and has been) debated."

But once again let me say there is NO DOUBT that re-forming of an electrolytic cap is a legitimate process, and is recognized as such by the major capacitor makers.

But reforming is not magic! It does not restore a cap to proper performance in every case - some are just too far gone. And it can be done improperly and that can be trouble. There is a way to determine if the reforming process has been successful, and there is also a need to physically examine the cap, checking for warm/hot spots during reformation.

I've personally applied my reforming process to 100s of caps, and I'd say about 80% were successfully reformed. The 20% that were rejected were tossed either due to high DC current flow through the cap even after the proper reforming process was done; or I felt hot spots on the cap during the reforming process. A few vented on their own or started to distort the case.

That DC current thing is important. It's heat build up inside that causes those "exploding cans". The heat is a result of current flow through the cap. For instance, a cap exposed to 400 volts that has 1 ma of leakage has to dissipate .001 x 400, or 0.4 watts. At 10 ma leakage it becomes 4 watts and that is a significant amount of heat - more current flow = more heat. It could cause a cap to vent to relieve the internal pressure. And yes, I am ignoring the impact of the ripple the cap sees to keep this simple.

The caps I've successfully reformed show DC current leakage at a fraction of 1 ma. - usually under .25 ma. at 10% over maximum rated voltage on the cap.


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  • RE: The fallacy of "reforming" capacitors - Jim McShane 14:08:08 12/23/15 (0)

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