NOS Caps & Possible Leakage

[Blackburn]

I've read a little bit about some old caps becoming leaky even while NOS, due to their construction, where they were stored, how much they've been handled, etc. I ask, because I found what appears to be a good deal on some old ones that look NOS and while cheap, I don't want to be giving away the cash for useless junk. Any opinions on the subject would be much appreciated!

David

[ApexJr.]

I've been told it's mainly what type of caps, some of the older
Vitamin Q caps are great and do not leak, the older bumble Bee
type cap leak very badly, electolytics have a 20 year life cycle
and sometimes be reformed.....

It's really the type of cap...

[selloutrr]

Correct.

Most electrolytic capacitors have a shelf/operating life of ten years.
After which point you can thing of them as a classic car. If its been regularly used and kept running its possible its still good however most that have set un run need serious restoration.

[Blackburn]

Thanks for the tips, guys. I'm speaking solely of signal caps, though. They seem to be cheap enough that it shouldn't be that bad if I lose out, since it really isn't much money.

[Phil_S]

I found what appears to be a good deal on some old ones that look NOS and while cheap, I don't want to be giving away the cash for useless junk.

There is a reason they are cheap. As already stated, there is a finite shelf life. Look elsewhere. Today's manufacture of caps makes them physically smaller, closer tolerance to spec, and cheaper. There is little or no justification for not buying fresh caps. Avoid NOS, as there is no mojo in them.

Edit: I see while I was posting you clarified the product. Signal caps tend to be OK when old. Just the electro-caps that should be avoided. If cheap and you want to take a chance, I'd say why not. Only spend what you can afford to flush down the crapper, though. Low expectations will help improve the chance of success.

[Blackburn]

I found what appears to be a good deal on some old ones that look NOS and while cheap, I don't want to be giving away the cash for useless junk.

There is a reason they are cheap. As already stated, there is a finite shelf life. Look elsewhere. Today's manufacture of caps makes them physically smaller, closer tolerance to spec, and cheaper. There is little or no justification for not buying fresh caps. Avoid NOS, as there is no mojo in them.

Edit: I see while I was posting you clarified the product. Signal caps tend to be OK when old. Just the electro-caps that should be avoided. If cheap and you want to take a chance, I'd say why not. Only spend what you can afford to flush down the crapper, though. Low expectations will help improve the chance of success.

I completely agree about NOS lytics. I don't have any interest in those and don't believe they hold mojo either. The oldest ones I bought were the Rubycons, just for their intrinsic value. That, and compared to new Spragues, the cost seemed justified.

Thanks for the info about the film caps. I think I'll buy some of them, if not all.

[cbass]

I've had good luck reforming NOS old electros.But I probably don't know any better.

[katopan]

Film caps you're probably going to be OK. Paper in oil can be gold or can be leaky (literally) dripping oil into your amp.

[selloutrr]

If you want to try to reform / test old caps I've had good success with a sencore LC-102 and 103.

Though I've noticed if the caps aren't used regularly after forming they drift quickly.

[Prairie Dawg]

I bought out several cabinets of NOS caps from an old radio shop. The Sprague 4HT and 6HTs were fine but I tossed away several hundred Mallory bakelite cylinder caps because they all leaked badly.

[rp]

I've played around a lot with old caps as they are a very real part of the magic mojo if trying to clone a vintage amp, that plus voltages and speaker. Forget wax caps completely, the Bumblebees too, as for the yellow / blue ajax / astron molded types + Sprague, CDE, Chiefs, Pyramids greenies, blacks, reds it's total hit or miss - you will have to pay and you will have to eat a lot of them, maybe 50%, simply no way around it. I've bought off ebay, e.g. 15 caps, and had 100% turn out worthless - some good sellers will take them back or state as is.

Test them all for capacitance first and if very close to spec you're odds improve for leakage, but that's moot as you're not going to use off spec caps anyway. If I was still in the States I'd have hunted down an old high voltage cap tester off ebay, but otherwise if the amp sounds great and the voltages are on spec and no scratchy pots you prolly got lucky. After that if still in doubt you can lift one end and test them in circuit. For post molded era caps, 70s-80s, NOS seems as reliable as new modern. And, used or NOS 60s-70s mustards seem very reliable. I only use NOS caps for myself, I don't think I'd ever sell or fix an amp w/ them, except maybe the mustards.

[Blackburn]

After a good ten days of vacation, I finally put down the money on the rest of those caps. They were hit pretty good while I was away, so I decided on taking the seven that remained.

Hope none of them leak!