Old Aluminum Electrolytics

Don't those break down more from use than age?

They are not sealed. They dry out.

Hermetically sealed military Al EL caps do not have this issue. Usage *may* accelerate it with cheap brands and the low end of the line. Usually, the 85°C versions or even the 105°C jobs last a good many years. They have tighter manufacturing controls on them or their manufacturing failure rates climb too high.

So, they dry out.

Like your brain would, if there was any there.

"TheQuickBrownFox"

** Electos are all sealed - but the seal can fail with age and heat and is not 100% impervious to the electrolyte. ** Heat accelerates the loss of electrolyte through the seal - such heat may be environmental, internally generated or both. ** Electros can last 50 years or more - or at least it is true to say that many electros made 50 years ago are still functional. ** The main failure mode of old and unused electros is " de-polarisation ". A depolarised electro has a higher C than before and a lower working voltage - in inverse proportion.

This can sometimes be reversed by slowing bringing the electro up to rated voltage so it can reform internally - but I would never trust the cap afterwards.

BTW: Makers use several times more electrolyte inside an electro that is strictly needed for it to function - so a loss of some electrolyte has no effect on performance.

.... Phil

How much would it cost you to replace them?

John

I don't know what the odds are but I have a number of old electros and, so far, they've all tested good, at least for capacitance. I haven't checked leakage.

I use them only for prototyping.

Depends on the quality level. Really good quality old ones are probably fine--they were sealed well, so they didn't dry out easily.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net

and is

.

heat

s.

t

".

d

is

has no

Thanks for that Phil, George H.

High, if they've been stored at room temperature. You wouldn't use them in a product, but they're fine for prototyping, experimenting, throwing together a quick temporary circuit, that kind of thing.

Ed

I'm using a 160,000 uF capacitor from a PDP-10 to recondition NiCd cells; it's older than your little quarter-century units by about 150%. The sparks are still fat and healthy. Bulky, though: about a foot tall.

It won't last long with you shorting it out when it is charged all the time.

"whitless"

** Not likely.

How about older by 50% ?

.... Phil

=A0 =A0 ...Jim Thompson

=A0 =A0| =A0 =A0mens =A0 =A0 |

=A0 | =A0 =A0 et =A0 =A0 =A0|

=A0|

=A0 =A0 =A0 |

Hej Jim

Check them with a (homebuild) ESR-meter:

Capacitor Testing, Safe Discharging and Other Related Information Version 2.42 (22-Nov-05):

Quote: "... Before I bought my ESR meter I too wondered--what exactly did it measure? Nevertheless, having heard so much about the meter, I went ahead and bought one. It works, and that's the real bottom line. ... The objective of the ESR meter is to identify capacitors that have gone bad. This is more the case with electrolytics where the dielectric compound tends to dry up. ..."

Equivalent series resistance:

The electrolytic cap ESR problem, and this meter...by Bob Parker the designer of the ESR Meter Kit (Mark 1):

Quote: "... The real fault with many of these electros was not so much that their capacitance had dropped (as many people assume), but their Equivalent Series Resistance (ESR) had risen to a high value, seriously degrading their effectiveness as filtering, bypassing and coupling components. ..."

Hints for techs using Bob Parker's ESR meter(kit)...:

Citat: "...Bob Parker's excellent ESR meter (January 1996) will also test all types of cells and batteries..."

Bob Parker's ESR Meter Page:

Citat: "... Display: 2x high efficiency Super-Red GaAlAs Kingbright SC56-11SWRA 7 segment LED displays...."

Citat: "... Table of approximate worst-case (highest) ESR values for new electrolytic capacitors at 20 degrees C (68'F). ESR generally decreases with increasing temperature. ...

10,000uF...0.12 [Ohm for 10V] ...0.08 [Ohm for 16V] ...0.06 [Ohm for 25V] ...0.04 [Ohm for 35V] ...xxx [Ohm for 63V] ...xxx [Ohm for 100V] ...xxx [Ohm for 250V] ... Notes: These figures are a guide only! Some electrolytics (especially high temperature types) can give higher readings and still be OK. Others can read significantly lower and be OK. In general, be wary of a capacitor with an ESR reading more than double the figures shown here. If you get a reading less than half, check the capacitor with an ohm meter... it might be shorted.

Written November '98, by Bob Parker [

] ..."

Other ESR-meters:

An Equivalent Series Resistance Meter:

An Equivalent Series Resistance Meter (without microcontroller):

Citat: "...With my ESR meter I quickly found five electrolytic capacitors which had degraded a lot...one had 6 Ohm, one 7 Ohm, and the other two had such high ESR that the meter wouldn't even deflect!..."

Building an ESR meter for Testing Electrolytic Capacitors (without microcontroller):

ESR & Low Ohms Meter Page (K-7204 original) K-7214 (MK2):

The "Genie" ESR capacitor tester & Low Ohms Meter

Yes, if the box smells like cat piss.

-- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.)

--------------------------------------------------------------

"Greegor" Jim Thompson

Don't those break down more from use than age?

** Some do, some don't.

I just dragged out the oldest electro that I bother to keep in my junk ox - a 5,900uF, 85V screw terminal type made in the USA by "Sangamo" carrying the date code 7836 - indicating it was made back in September of

1978.

This electro spent the first 9 years of its life in the PSU of a Phase Linear 400 audio amplifier - until its partner died prematurely. Both were then replaced with new 10,000 uF, 100V types.

The Sangamo tests as having an ESR of 8 milliohms and leakage current at 90 volts DC of just 50uA.

Which is equal to the new spec.

.... Phil

"Jim Thompson" schreef in bericht news: snipped-for-privacy@4ax.com...

As so often, it depends. Mainly on initial quality and usage/storage. Sometimes I have to repair vintage tube radios in which electrolitics of over 60 years old still function properly. If the caps are not used for a long time I advise to raise voltage slowly to reform whatever part of the dielectricum might have gone. So you can use them for your goals, especially as you do not do (mass) production anyway.

petrus bitbyter

Jim Thompson wrote in news: snipped-for-privacy@4ax.com:

you may need to "reform" them;bring them up to working voltage slowly for the first time. after that,I suspect they'll be fine.

--
Jim Yanik
jyanik
at
localnet
dot com

I'd guess that almost all of them are presently rather leaky, and would benefit by a gradual re-forming (if you turn the power on suddenly, some of them might go FOOM).

A lot of them have probably dried out at least somewhat and gone high-ESR.

I wouldn't use them for anything critical, and if I used one for a junk-box application I'd charge it up to its WVDC gradually (1-meg series resistor, a few hours of soaking), check for leakage, discharge, then test on an ESR meter.

Probably easier to just toss 'em in the electronics-waste bin and buy fresh ones... unless you've got loads of time to kill, the effort to weed out the bad ones and find the good ones is probably more than they're worth.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!

Almost all of them would be OK..just bring up the voltage slowly and let them re-form for about an hour.

I've reformed many caps with a 1k to 10k resistor in series, with the bench supply voltage set at 110 percent of the cap's rated working voltage. Good ones go down to well under one mA leakage, bad ones just stay leaky and never charge up to even half rated voltage.

I'm thinking it's a good idea to plug in and turn on all "sitting on the shelf" equipment once or twice a year for a few minutes or hours, if for no other reason than to make sure the electrolytics stay formed.