Out of spec vintage Sprague caps worth keeping?

[M. Spencer]

I recently stumbled upon a small lot of vintage Sprague and the like electrolytic capacitors, and after measuring and sorting I am left with quite a few with super short leads or totally out of spec. The ones I kept were basically within 20% of printed value; but many were double the printed value or more.

From what I understand, especially, old electrolytic caps go bad usually due to the deterioration of the dilectric. Is that what would cause their capacitance to increase?

Are these worth keeping and potentially using, even so out of spec?

(Not intending to rekindle the debate over MOJO or NO-JO, let's just assume some of us like handling the old stuff for kicks)

[Silver Blues]

I should think that deterioration of the dielectric would cause their capacitance to go down, not up, just by virtue of how a dielectric in a capacitor works. Maybe they're just poorly quality controlled? There was a project somewhere here for an ESR meter for capacitors that might help you figure out if they're bad.

[rocket88]

i've got to agree with silver. electrolytics usually go down in capacitance with time. this is the main reason that why it's important to replace them in vintage amps, especially the bias. i have a similar issue with my gibson rd artist restoration. the original moog active electronics have a fair bit of electrolytics, and i know i should probably replace them, but probably wont.

[M. Spencer]

Ok I figured the capacitance would decrease as they got old, but was confused by how many of the were way above their stated values.

Now the real question: when I start using these, how long before they crap out and I have to replace them? 🤔

[motterpaul]

Just out of curiousity, do you have a capacitor tester on your DMM? If not, you can buy one for a reasonable price at Amazon.

I got one of these and it is well worth the cost to be able to see exactly if a cap is good or not:

https://www.amazon.com/DMiotech-Multimeter-Digital-Capacitance-Capacitor/dp/B011HIKGZC/ref=sr_1_13?ie=UTF8&qid=1487608472&sr=8-13&keywords=capacitor+tester

(I actually thought I paid less, you might google for a lower price, or look for a private seller)