Best way to freshen up electrolytics sitting in the bin?

[80k]

I understand that electrolytic capacitors don't like sitting unused for too long. I have a fair amount of old electrolytics that are 6+ years old (possibly much longer, as some were bought in an old surplus store, and who knows how long they were there before I bought them). I've recently used some of them for a project and they didn't cause any problems.

I'm thinking I should find an easy way to "freshen" them up by running some voltage through them. What would be the easiest way to set something up where I can just plug in a bunch of electrolytics into a breadboard and run some voltage through them for maybe an hour or so? Is this even worth it? I know electrolytics are cheap and I can just as easily replace them, so maybe this is unnecessary.

[Paul Marossy]

I understand that electrolytic capacitors don't like sitting unused for too long. I have a fair amount of old electrolytics that are 6+ years old (possibly much longer, as some were bought in an old surplus store, and who knows how long they were there before I bought them). I've recently used some of them for a project and they didn't cause any problems.

I'm thinking I should find an easy way to "freshen" them up by running some voltage through them. What would be the easiest way to set something up where I can just plug in a bunch of electrolytics into a breadboard and run some voltage through them for maybe an hour or so? Is this even worth it? I know electrolytics are cheap and I can just as easily replace them, so maybe this is unnecessary.

I've used some pretty old electrolytic caps in many of my projects, they all worked fine.

I think it matters more on the high voltage type caps, like the "can" caps in an old Marshall for instance. I've had one of those blow up on me before. It was on an amp that had been sitting in a HOT garage for a few years and never fired up the whole time it was in storage.

[80k]

I've used some pretty old electrolytic caps in many of my projects, they all worked fine.

I think it matters more on the high voltage type caps, like the "can" caps in an old Marshall for instance. I've had one of those blow up on me before. It was on an amp that had been sitting in a HOT garage for a few years and never fired up the whole time it was in storage.

yea i'm surprised how well my old electrolytics have served me over the years. But I also wouldn't want to press my luck!

Some of my favorite pedals have a bunch of 1uF electros in them, and I wish I'd known about the 1uF film caps back then, which I am now using on all my circuits whenever I can.

If I do want to run voltage through a cap, any idea on the best way to do it? Can I simply hook a 9V battery to the negative and positive leads, and maybe a resistor in series?

[aron]

These links might help:

http://geofex.com/tubeampfaq/TUBEFAQ.htm#forming

http://www.davehylands.com/Machinist/CNC/CNC-Controller/01-Condition-Caps.html

[sean k]

Yeah, I remember asking Simcha Delft (the man who designed the moonlight amp) about this and all I can remember is putting ac accross the caps and a load so those explanations above clarify that for me. I'll go get a 5W 100k resistor.

I've always used old stock multi caps in my tube amps which have always been a bit noisy and this may be because they are degraded. What I remeber from Mr Delft as well is that these degraded caps can be reformed so maybe this'll fix up my amps.

[petemoore]

  Observe and follow polarity, apply only DC to polarized capacitors.
  Observe voltage rating, applying 10% less than that is fine.
  Follow the rules and you should be fine.
  Don't touch the leads of caps charged to >30v.
  "Cycle" is what I read, so I guess that means 1.
  Not sure what re-cycling does other than make them better or worse, ie, unplug, settle, replug in, and see if the waterfall and ''dorito crunching'' stops, not sayin' this always helps, only reporting that you too may notice that cycling sometimes changes the algorythms of leakage related noises.
  Over time the charge will dissipate, or a resistor [say 10k] could be used, such as the 22k I use to discharge caps in amps, I'm not sure what loading to decrease discharge time would do, ...IIRC it's something about introducing a voltage charge sometimes reforms the dielectric insulator.

[frank_p]

Really don't know what is the value of that:
http://phonoclone.com/diy_rack.html

Build (or buy) an esr meter.
And:
http://www.diystompboxes.com/smfforum/index.php?topic=72006.msg581498#msg581498