Cap life span?

I have a CJ PV-10A circa 1992. The Solens film caps in it while not the greatest caps never showed any noticeable agingissues. However the white "CJ" film caps definitely aged, deadening highs and transients; swapping with new caps gave immediate improvement. So cap type must have some bearing on life span.

I recently put a Technics DD turntable from the late 80's back into service. I replaced EVERY electrolytic AL cap. Many were starting to show corrosion at one electrode.

Please remember you cannot judge the quality of 20 yr + old AL caps by specs of today's products. Back 20-30 years ago they were not as good as today's premium brands (not the cheapo stuff).

I have Tektronix O-scopes and electronic equipment from the 70's which used a lot of solid tantalum electrolytics. I have yet to see one of these fail. They are vastly superior to Al electrolytics from a lifetime perspective.

Although Tantalum caps are considered, "electrolytic"; there is no liquid electrolyte(totally different construction) to dry out, or expand and blow out the vent. Two major reasons for electrolytic failure. Solid polymer(ie: PEDOT) electrolytics are another excellent option, if applicable. Try finding either, in a value usable for a power amp PS filter cap though. I've installed Sanyo OS-CONs in my TACT preamp's PS, with excellent results.

Rodman:

Yes, that is why tantalums are called "solid", although some military versions actually have a liquid electrolyte in them (VERY EXPENSIVE). The solid versions use MnO2 electrolytes that are produced by evaporating the salt solutions during manufacture.

They are not designed for power supply main filtering, only bypassing and for timing circuitry. They have very low leakage currents, about 1/10 of the leakage through Al electrolytics. They range from about 0.1 to 200-300 mFd. Outside this range they are not applicable. The larger capacitance versions can be very expensive.

One audio application I have used them for is the timing circuits in my Parasound JC-1. Replaced the Al electrolytics that Parasound used stock with tantalums and now my turn on time delays (there are three of them, sequential) are rock solid.

I would not recommend them for audio coupling due to their non-linear dissapation factors and dielectric performance. But they last forever.

I like to rotate mine every six to twelve months. You know, so they get even wear. It sucks when you open up a case only to find one cap has all it's tread worn off and another looks brand new.

Hmmmm.... I'm thinking if two different things.

But seriously, this is a subject near and dear to my heart. Not only am I a lover of older SS amps (Citation 7.1/5.1, Acurus A250, Haflers, etc) but I also love to fiddle with older computers. I have a collection of motherboards from that wonderful period of the mid to late 90s when there was a batch of caps that had a stunningly high failure rate. On pretty much every one of those babies you can see the cap bubble. Yep, makes me want to get the ole soldering gun out right now.

Anyway, I've been trying to decide just when some of my amps need to be serviced. It is an expensive proposition, especially when you include shipping both ways. I'm hoping the Citations can run, say, another 30-50 years! (yea, I'm hoping that -I- can run another 30-50 years). ;)