when (time frame) to just replace old electrolytic caps ?

i am working on an old mid 80's circuit board that has some original 2200 uF/ 63V electrolytic caps (size of a C-cell) plus some others and was just wondering when one should just replace such a creature ?

says made in W-Germany "Elkorauh" if it makes a diference ?

should i remove and test them (maybe stress them ?) or just leave them alone (i.e. fix broken things) is there a life expectancy for electrolytics ?

thanks for help, robb

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We work on a shelf life of 10 years before needing reforming, assuming optimum ambient temp etc etc.

In service on continuous operation about 20 years before we replace.

We do refurbs on our older 30V switch tripping batteries and chargers, and we replace all the electrolytics and rectifiers, and the small transformer as well. Most of these come in when the batteries are at end of life, usually 7 years or so.

Bigger systems tend to be less of a problem as the caps are bigger and better quality.

Our preferred vendor was Philips/BC Components, but we are now using Rifa/Evox and BHC.


-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Peter A Forbes

Yes there is a life expectancy with electrolytics how ever, if you have tested these caps after some reforming time and found them to be ok, it may not be necessary to replace them..

One a second note: If you're restoring, It might be a good idea to do so.

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For the sake of reliability I would replace them after 5 years.

Its better to replace them than for them to pop and take something else with them.

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robb schrieb:

First off, "Elko" is short for "Elektrolytkondensator" (electrolytic capacitor), and "rauh" ("rough") refers to the electrode type. This kind of etched electrodes is standard; they result in higher capacitance per volume, while plain electrodes mean better behavior at high (i.e. upper audio) frequencies. And, generally speaking, you can expect electrolytic capacitors from Germany to be of high quality (i.e. to be comparatively long-lasting).

The life-time of electrolytic capacitors is primarily linked to electrolyte loss (i.e. evaporation) over time, which strongly correlates with ambient (storage or operating) temperature; it further depends on the quality of the seal, and on the (initial) amount of electrolyte they are meant to contain - larger capacitors can therefore be better than miniaturized ones.

According to their expected use (e.g. consumer versus industrial products, room temperature versus elevated temperatures), electrolytic capacitors are sold in different "endurance classes" which can be inferred from the labeling. The cheapest (consumer quality) electrolytics are typically rated >2000 hours (three months) at 85 degrees centigrade. However, even this usually translates into >300000 hours (thirty years) at 30 degrees. And still significantly longer at really convenient room temperatures. Industrial quality electrolytics (rated >2000h at 105=B0) can be expected to last at least twice as long.

Thus, at normal ambient and operating temperatures, even standard electrolytics can be expected to last a human life. Smoothing capacitors in power supplies that are noticeably heated up by the ripple currents they are expected to short-circuit, or by adjacent transformers or heat sinks, are usually more endangered. Unless your board is operated at elevated temperatures, or is safety-critical or would be hard to service because it will be installed in an inaccessible place, a prophylactic replacement after 20 years would usually seem unnecessary.


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Good Lord ! I'd say that was very premature with 'typical' use.


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Indeed. It's all about evaporation and diffusion through the seal, and you can't discuss this without discussing temperature. Electrolyte loss more than doubles for each temperature rise of 10 degrees centigrade. For specific numbers applying to a quality product of the ">2000 hours at 105 degree" type see


If you extrapolate the diagram at the top of page 19 to lower temperatures you easily arrive at life-times in excess of 100 years (10^6 hours) for low ripple-current loads.


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Hmm. 5 years?

I suggest: if it is "made in China" every 3 months if it is old Philips, and not used in high current or in a high temperature environments: 50 years or so

I have several old radio's etc with original componnents from the 50's and 60's that still work perfectly. Not using them is bad. Use them and if they have not been used for years, format the caps at low voltage/current.


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I run high power amplifiers that run quite hot so 5 years is a good time. I havent had any go short circuit yet so 5 years must be on the safe side.

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assuming optimum


chargers, and we

transformer as well.

usually 7 years or

bigger and better

using Rifa/Evox

thanks Peter, the application is fairly light duty sealed environment with low temps and little crowding, low temps and i think total usage time is pretty low with low strees to so i will probably just let them go on

thanks again for reply robb

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you have

be ok,

thanks for help and reply Jamie,

now i need to go google reforming capacitor :)

thanks for help robb

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behavior at

you can








longer at


as long.





safety-critical or


Thanks Martin.

for all the useful info, now i can use your parameters to determine if replacement is needed. i think they will not need replacement because the stress level ( hours of usage, heat, etc..) is fairly low.

these appear to be used in a stepper motor circuit and are placed far away from hot stuff

i was mostly concerned about deteriorating from just age alone, but your info helps me relaize that capacitor age may not be as important a factor on the 20 year scale

thanks again for all your helpful info, robb

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the 50's



thanks Pieter, i think these have average to low use and probably can be left to work for a few more years.

thanks again for help and reply, robb

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