Do capacitors go bad merely from age, or do they go bad from repeated charge and discharge?
I was wondering whether "new old stock" capacitors are actually okay to use, or whether a 30 year old capacitor is 'dried out' or whatever goes south with them. I have a junk shop nearby with many NOS caps that have never been soldered into anything.
Appreciate any insight on how they degrade. Happy holidays.
I was wondering whether "new old stock" capacitors are actually okay to use, or whether a 30 year old capacitor is 'dried out' or whatever goes south with them. I have a junk shop nearby with many NOS caps that have never been soldered into anything.
Appreciate any insight on how they degrade. Happy holidays.
Depends on the type. Ceramic capacitors are good for more than 100 years. (However do not use ceramic capacitors made before 1900!) Film capacitors usually more than 25 years. Oil and paper capacitors about the same if they haven't leaked! Electrolytic capacitors have a shelf life unused of less than 10 years and usually are expected to be used within two years from the date of manufacture. However some of them can be "reformed" by applying a low current high, voltage to them for a while. You should be able to find details on this site.
Thanks very much - that's interesting and good to know. I should have said, I was thinking of electrolytic capacitors. So the electrolytic caps being sold as NOS should be considered useless then.
It seems that these parts are among the things undergoing skyrocketing inflation. I went to do the filter caps in an old amps and found - wow, these capacitors are $10 each now?
It seems that these parts are among the things undergoing skyrocketing inflation. I went to do the filter caps in an old amps and found - wow, these capacitors are $10 each now?
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Everything is going up in price, including electronic parts. Just be thankful you can still get what you need.
jeff
jeff
Capacitors degrade due to temperature, age, storage conditions, use and construction. Even some ceramic capacitors degrade over time: https://product.tdk.com/en/contact/faq/capacitors-0043.html
I've found that Very old capacitors degradation (or failure) is mostly dependent from build technology and storage conditions. A case in point are the two 25V electrolytic capacitors on the attached picture. The bigger one is a Sprague built in 1967. The smaller one is a new Kemet capacitor, production date april 2022. They measure almost the same on my capacitor tester: same capacitance 30mF, same ESR (0.4 ohms), same loss factor 1%. So the 55 years old electrolytic capacitor is as good as new, and it does not exhibits any visible decay signs as well. The two capacitors, despite having similar electrical parameters and application, obviously aren't built with the same technology. Sprague traded off a substantially higher size, weight and cost for a much longer operational life. I've seen this technology also on some vintage Mallory and Philips capacitors. I also have seen many electrolytic capacitors that have gone bad, sometimes in less than 10 years. The purchase and use of NOS capacitors should be done with care and they always need to be checked.
I've found that Very old capacitors degradation (or failure) is mostly dependent from build technology and storage conditions. A case in point are the two 25V electrolytic capacitors on the attached picture. The bigger one is a Sprague built in 1967. The smaller one is a new Kemet capacitor, production date april 2022. They measure almost the same on my capacitor tester: same capacitance 30mF, same ESR (0.4 ohms), same loss factor 1%. So the 55 years old electrolytic capacitor is as good as new, and it does not exhibits any visible decay signs as well. The two capacitors, despite having similar electrical parameters and application, obviously aren't built with the same technology. Sprague traded off a substantially higher size, weight and cost for a much longer operational life. I've seen this technology also on some vintage Mallory and Philips capacitors. I also have seen many electrolytic capacitors that have gone bad, sometimes in less than 10 years. The purchase and use of NOS capacitors should be done with care and they always need to be checked.
The marketplace of consumers is buying thousands of them. I'm sure they're not grateful. But price increases have vastly outstripped wage increases and even producer prices. That's how you know the price is wrong. After all nobody needs an amplifier. Some people feel that they do, psychologically. I'm not one of them. 😉
Like pcan, I have found that many older caps age gracefully: I have posted many examples. Some don't: paper caps (dry ones, not PIO) degrade almost universally, irrespective of the manufacturer.
Ecaps, like the Sprague powerlytic or Mallory, or big Sic-Safco professional types seem to last forever: I still use examples dating back from the sixties.
For smaller caps, the situation is more diverse: Siemens made extremely good caps in the early seventies, Phillips had various phases, some good, some awful, just like Frako and ROE, and F&T was almost universally bad, like many British, US or French manufacturers.
Mylar caps should be better and more consistent, but it is not always the case: some suffer from humidity ingress and degrade catastrophically. Early British examples, like Hunts failed due to contamination.
German types were better, as were early Phillips types, like the "mustard" model.
Ceramic caps tend to be much more more durable, but they also have degradation and failure modes. Nothing lasts forever
Ecaps, like the Sprague powerlytic or Mallory, or big Sic-Safco professional types seem to last forever: I still use examples dating back from the sixties.
For smaller caps, the situation is more diverse: Siemens made extremely good caps in the early seventies, Phillips had various phases, some good, some awful, just like Frako and ROE, and F&T was almost universally bad, like many British, US or French manufacturers.
Mylar caps should be better and more consistent, but it is not always the case: some suffer from humidity ingress and degrade catastrophically. Early British examples, like Hunts failed due to contamination.
German types were better, as were early Phillips types, like the "mustard" model.
Ceramic caps tend to be much more more durable, but they also have degradation and failure modes. Nothing lasts forever
To answer the original question, old high-spec electrolytic capacitors are still useful at least for uncritical application such as linear power supplies, provided they have been stored properly. Ther same is true for old recovered capacitors that never experienced overheating. I recover known brands such as Nichicon long-life series, from discarded boards that are at most 15 years old. I've rarely found this kind of capacitors inside consumer electronics, but they are popular on floorstanding office printer/copiers and industrial power supplies, inverters, and other products that are designed for a longer life span. According to my experience, a recovered capacitor of this type does usually measure better than a brand new cheap capacitor from China, and I guess that the remaining lifespan is greater too. A capacitor tester is required to check recovered capacitors. I have access to high-spec film capacitors that have been replaced due to 5-years scheduled maintenance of power inverters. They look like new but they measure very bad, capacity and leakage barely inside specification or worse. The same is true for first generation solar inverters that have been replaced due to refurbishment: many good looking electrolytics from good brands on the board, but they are severely degraded due to overheating and bad environement conditions.
Electrolytic capacitors are water filled aluminum bottles sealed with an elastomer (rubber). Except for epoxy sealed ones, which are as rare as unicorns.
Rubber is attacked by oxygen. There are different grades of sealant. Some degrade & crack in a year, some 20 years or more. When you buy new ones, you can buy 500 hour service life ones, you can buy 12000 hour service life ones. I tend to buy the latter.
People frequently buy an old electronic device, check that it is working, and after a few dozen hours of use, it doesn't anymore. There was water in the e-caps at first, which gradually evaporated by the heat of operation.
The mallory can caps in my 3 Hammond H100 organs, those were all trash when I bought them 2015 to 2018.
Sprague atomlytics & blue beavers I bought from the TV parts store about 1972, were worn out by 1978 in my ST70 amp after ~12000 hours use. Evidence, the B+ and cathode bias voltages were way off.
No capacitor tester tests the amount of water in the cap, versus what was in there when it was shipped from the factory. No capacitor tester tests the integrity of the seal.
So no, I don't buy NOS electrolytic caps. They may work for a while, particularly the enormous "computer grade" ones from 1980 & before. Green CDE's from the 70's, those are worth their weight in platinum. Those were the epoxy sealed ones.
Rubber is attacked by oxygen. There are different grades of sealant. Some degrade & crack in a year, some 20 years or more. When you buy new ones, you can buy 500 hour service life ones, you can buy 12000 hour service life ones. I tend to buy the latter.
People frequently buy an old electronic device, check that it is working, and after a few dozen hours of use, it doesn't anymore. There was water in the e-caps at first, which gradually evaporated by the heat of operation.
I have Wurlitzer 4500 & 4502 organs from 1966 chock full of useless Mallory caps. About 220 of them. They made a good cap, if you would pay the premium. Wurlitzer didn't.
The mallory can caps in my 3 Hammond H100 organs, those were all trash when I bought them 2015 to 2018.
Sprague atomlytics & blue beavers I bought from the TV parts store about 1972, were worn out by 1978 in my ST70 amp after ~12000 hours use. Evidence, the B+ and cathode bias voltages were way off.
No capacitor tester tests the amount of water in the cap, versus what was in there when it was shipped from the factory. No capacitor tester tests the integrity of the seal.
So no, I don't buy NOS electrolytic caps. They may work for a while, particularly the enormous "computer grade" ones from 1980 & before. Green CDE's from the 70's, those are worth their weight in platinum. Those were the epoxy sealed ones.
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get yourself an esr tester, your safest bet....
https://www.lazada.com.ph/products/...&spm=a2o4l.searchlist.list.i18.f3b5f69exT4KRL
https://www.lazada.com.ph/products/...&spm=a2o4l.searchlist.list.i18.f3b5f69exT4KRL