Rebuilding large filter caps? B&K Bench supply

[Naysayer]

I stumbled on an Audio site that mentioned rebuilding large electrolytics for less than purchasing new (https://www.nmr.mgh.harvard.edu/~reese/electrolytics/). I never knew that was an option. I have a McIntosh that needs 2 large caps and the cost has kept me from doing it.

Got a new-to-me bench supply I recently got from eBay. It's a B&K 1601, 0-50v at 2A max with continuously adjustable current limiting. Late 1970's vintage but good cosmetics. I replaced all the caps and few things that needed it. After re-soldering some loose connections, the single 3055 went out so i replaced it w/ a 3772 (a real one) I've been hoarding. Anyway that got me started replacing caps on my Pwr supplies. When did electrolytics get so expensive? It's been awhile.

Reconditioning NOS caps, I'll let them sit for awhile.

I'm about to resume the 2x 4cx300 amp project. I was getting just under 100W out of it when the PS I was using for my test rig expired and that started the re-capping effort. That was about 2 months ago.

neil, NYC

 

[loosecannon]

yes caps can be re-formed, but it's not going to make them like new again, and it's not really a reliable solution.

the reforming of caps is usually done in pieces of equipment that you would not want the liability of replacing the caps yourself, such as a variable frequency drive.
LC

 

[nomadradio]

My experience with this was pretty uniformly bad. But then again, hobbyists with persistence could get better results. A cap that has shorted internally at some point may appear to fix itself. What I have found is that after a HV capacitor goes "SNAP!", and then heals itself later will always have a shrinking voltage rating. A 450 Volt cap that had an internal short will tend to break down at 350 or 400 Volts after that. Every subsequent time it goes "SNAP!" it may heal itself again, but the voltage that will cause it to break down is once again lower than before.

My incentive is a stable result my customer can rely on. For my purposes, this means new caps. A breakdown after the repair costs way more in wasted labor than the price of the parts.

As a result, my approach has always been to start over with new parts.

But hey, it's your time to waste if you want to experiment with "re-forming" electrolytic caps. Folks out there write about it with great confidence. Color me skeptical. Your mileage may vary.

73