What is the expected lifetime for an electrolytic capacitor?

It varies hugely. Some have lives of thousands of hours, some of over a century.

Ripple current also affects them.

Capacitors failng to do the job are often not down to bad caps, but rather bad design with insufficient margins.

I'm no fan of replacing good caps with other good caps that are just as likely to fail, but if you've found bad caps in there then any others the same make are probably best replaced.

NT

On many consumer goods *all* the electrolytics are the same make. I'm not in favour of the shotgun approach unless you are certain there were batch etc problems at manufacture.

Coincidentally, I've just fixed four identical radio tuners all with the same fault. They were installed in a hotel and were on 24/7 power, and all failed within a short time of one another. The fifth one strangely still works ok.

The fault was a 22µF 63v electrolytic which is in series with one transformer winding and that rectifier followed by a voltage regulator. Dunno why they used this rather strange - to me - arrangement. Three were open circuit on my ESR meter - the fourth read 55 ohms. It took some finding as the output from the (discrete) voltage reg circuit was 5 volts instead of 30 and not being able to read the zener value without removal I assumed 5 volts was the correct amount...

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    Dave Plowman        dave@davenoise.co.uk           London SW
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No.

OK

No need to guess-- go to the digi-key catalog and look at the specs. The lifetimes are a heck of a lot shorter than you might expect.

-- just a few thousand hours at the "rated" temperature.

Then again some of us have 65 year old tube radios with the original electrolytics.

The only way to tell is to measure each dang one with a cap or ESR meter. For example many Tek 22xx series scopes need new PS capacitors as the original ones were of marginal quality. And many small caps, under 10uF, have dried out much faster than the larger ones and now are more like resistors than capacitors.

A? (as in "Canadian, a?" - ducking now! eh?)

John :-#)#

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"Old pinballers never die, they just flip out."

I recently came to a sad realization...I'm gonna have to quit buying (newer) old equipment with the expectation of fixing it.

Was an HP LCD monitor. The cap on the output of the swticher had failed putting 20V pulses on the

5V supply line. Fixing the cap didn't help 'cause the 20V had taken out the control processor and who-knows-what-else.

Switcher designs I've seen use the cheapest available components and have no prevision to limit voltage when the output cap opens...and given the extreme stress placed on it by the switcher, it will...eventually.

I predict this time bomb is gonna have a profound impact on the used equipment market.

mike

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shortest sentence solved!

A good point, and one I've become mindful of as I've crawled around the insides of the Fluke signal generator. It's full of rare integrated circuits, and I imagine some were designed for production of that specific instrument. Replacing caps is no big deal, but if any of those chips go south, I'm probably screwed. I suppose I could attempt to order replacements from those idiotic sites--the ones you find using Globalspec.com or any of those other annoying search engines--but I've read that they only deal with industrial buyers that purchase in large quantities.

-Dave

Lifespan is determined by too many factors to predict. Capacitor quality, temperature, circuit characteristics, it can range from months to decades.

??????????? Isn't that rather what I was saying in that thread last week, when you were contending that a 40v cap is good to 40 volts long term, and implying that by saying anything different, I did not know what I was talking about? Sorry to bring it up, and I really don't want to start all that up again, but I was gobsmacked when I read what you now seem to be saying ...

Arfa

I think some just fail with age and lack of use too, then fail when voltage is reapplied. Last week i repaired a portable cassette recorder with extremely noisy hissy output with the programme material almost inaudible. there were two caps, a 220uF and 100uF 16v I think , across the output stage of the amp. Both were within operating voltage, looked fine no bulging etc. but this machine had been sitting for decades without use.

You misunderstood what I was saying significantly, and following your last response I doubt there's any mileage left in the discussion.

NT

Classic "drying out" of electrolytics. No use needed. Heat speeds the process, but not required for the end result.

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Al, the usual

Yes, you are right that there is no further mileage in the discussion, and I meant what I said about not wishing to pursue it further, nor do I now, but I think that I have got to leave it this time by saying that if I significantly misunderstood what *you* were saying, then you for sure misunderstood what *I* was saying ....

Arfa

As you said, it depends on a lot of factors. Temp, circuit design and the quality of the caps are more important. An ESR meter is very handy in cases like yours. It's not unusual to find a few totally bad caps when the rest are fine. On the other hand, I've seen plenty of cases where every last cap is bad. Andy Cuffe

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