Electrolytic caps?

[Melissa]

I used to work in electronics and have several large boxes of electrolytic
caps in my lab. Does anyone still use them for anything? Is there even any
electronics still being built in this country?

 

[Michael A. Terrell]

I used to work in electronics and have several large boxes of electrolytic
caps in my lab. Does anyone still use them for anything? Is there even any
electronics still being built in this country?

What type / voltage/ capacitance are they?

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

I used to work in electronics and have several large boxes of electrolytic
caps in my lab. Does anyone still use them for anything? Is there even any
electronics still being built in this country?

Yes and yes, but it depends on how old those caps are. Over five years
old, and they're not 'fresh'; ten years and they're 'stale'.

 

[Joerg]

Hello Watson,

Yes and yes, but it depends on how old those caps are. Over five years
old, and they're not 'fresh'; ten years and they're 'stale'.

Nah. I have some 40+ year old radios where the electrolytic caps are
just fine. A couple times I actually did a resistor charge and leakage
test just to see. They were nearly as good as new.

But sometimes when they had been in storage for decades they may have to
be "formatted" slowly to get them used to the job of "being a capacitor"
again.

Regards, Joerg

 

[Jim Thompson]

Hello Watson,


Nah. I have some 40+ year old radios where the electrolytic caps are
just fine. A couple times I actually did a resistor charge and leakage
test just to see. They were nearly as good as new.

But sometimes when they had been in storage for decades they may have to
be "formatted" slowly to get them used to the job of "being a capacitor"
again.

Regards, Joerg

Hi, Joerg. I do, literally, have some 40 year-old aluminum
electrolytics in my part bins.

What's the best way to "format" them?

...Jim Thompson

 

[John Woodgate]

I read in sci.electronics.design that Joerg <notthisjoergsch@removethisp

Hello Watson,


Nah. I have some 40+ year old radios where the electrolytic caps are
just fine. A couple times I actually did a resistor charge and leakage
test just to see. They were nearly as good as new.

But sometimes when they had been in storage for decades they may have to
be "formatted" slowly to get them used to the job of "being a capacitor"
again.

It took a long time to discover that sodium chloride (common salt)
contamination was responsible for short life of aluminium electrolytic
capacitors, simply because traces of salt are almost everywhere. So if
your old caps have, by chance or design, a low salt content, they may
well still be good.

 

[Tim Wescott]

Hi, Joerg. I do, literally, have some 40 year-old aluminum
electrolytics in my part bins.

What's the best way to "format" them?

...Jim Thompson

Its "forming" (technically "reforming" since it was already done once at
the factory long long ago). You can do a web search on electrolytic
forming.

Basically you feed it rated voltage through a big current limiting
resistor -- what you're doing is restoring the aluminum oxide layer on
the foil. There are a number of techniques for verifying that the
forming is complete (vs. the cap being bad) -- basically when you think
you're done you test with more than the rated voltage to see if the
thing leaks -- if so, you scrap it.

I've never done it, but it's a common thing with tube-equipped boat anchors.

 

[Spehro Pefhany]

Hi, Joerg. I do, literally, have some 40 year-old aluminum
electrolytics in my part bins.

What's the best way to "format" them?

...Jim Thompson

It's actually "reform". Here's a web site that describes the process:

http://www.vcomp.co.uk/tech_tips/reform_caps/reform_caps.htm


Best regards,
Spehro Pefhany

 

[Michael A. Terrell]

Hi, Joerg. I do, literally, have some 40 year-old aluminum
electrolytics in my part bins.

What's the best way to "format" them?

Jim Thompson

I prefer to go for "High density".


Actually, after you re-form the oxide layer with a limited current
(<.1 ma) at the rated voltage you check the ESR to made sure the cap is
good. Any signs of leaked electrolyte automatically makes it a bad
part.

 

[Grass roots]

Yes and yes, but it depends on how old those caps are. Over five years
old, and they're not 'fresh'; ten years and they're 'stale'.

And that means what?

 

[Melissa]

What type / voltage/ capacitance are they?

I don't recall, I'd have to go look. I have boxes of them all over the
place in my lab, which still hasn't been unpacked since we moved.

--
Yours In Liberty, Melissa - Colorado, U.S.A.
http://melissasliberty.blogspot.com/

The last best hope for liberty, to give the world its first Bill of
Rights: http://www.UPAlliance.org/billofrights.htm

 

[mc]

Its "forming" (technically "reforming" since it was already done once at
the factory long long ago). You can do a web search on electrolytic
forming.

Basically you feed it rated voltage through a big current limiting
resistor -- what you're doing is restoring the aluminum oxide layer on the
foil. There are a number of techniques for verifying that the forming is
complete (vs. the cap being bad) -- basically when you think you're done
you test with more than the rated voltage to see if the thing leaks -- if
so, you scrap it.

I've never done it, but it's a common thing with tube-equipped boat
anchors.

The way I do it, which I thought was standard, was to gradually raise the
voltage from zero over a period of minutes, monitoring for leakage all the
time, and then leave it charged to the rated voltage for some time.

You can measure quite an increase in capacitance from doing this, even if
the capacitor didn't test out as defective to begin with.

 

[John Woodgate]

I read in sci.electronics.design that Michael A. Terrell

Actually, after you re-form the oxide layer with a limited current
(<.1 ma) at the rated voltage you check the ESR to made sure the cap is
good. Any signs of leaked electrolyte automatically makes it a bad
part.

Both residual leakage current and ESR are important, but for ESR you
need some guidance on what is 'good' and 'bad'. It depends on a number
of factors.

 

[Michael A. Terrell]

And that means what?

It means that caps made during certain time periods and some
companies are prone to failure from dried out seals and depending on the
electrolyte used, the cpacitors may neeed to be re-formed.

 

[Michael A. Terrell]

I read in sci.electronics.design that Michael A. Terrell


Both residual leakage current and ESR are important, but for ESR you
need some guidance on what is 'good' and 'bad'. It depends on a number
of factors.

I try to find the OEM specs for the cap and check it with my Bob
Parker ESR meter. Failing that, I compare the capacitor(s) to others on
hand, or to the specs of similar caps from other OEMs.

I have been running about a 50% failure rate for new old stock and
salvaged electrolytics over the last year. I did the tests to entertain
myself while I couldn't work, and had nothing to do and couldn't get on
line for a year.

I used to have a Sprague TO-6 capacitor analyzer to check capacitance
and leakage. I'm thinking about designing a digital unit to replace it
and maybe sell kits.

 

[BFoelsch]

Personally, having played with electronics and salvaged parts since the
early 1950s, I think the whole "reforming" thing is pretty much baloney.

It's true, sometimes if you take an old electrolytic that tests poorly you
can get it to improve by using the "reforming" process. Often, however, the
resulting cap will have high ESR, and will want to leak for a while every
time you apply voltage to it.

I find that, in general, unless the leakage gets down to where it should be
in not more than maybe 15 seconds, the reformed cap is going to "deform"
spontaneously. There are some caps that will stop leaking over maybe 30
minutes, but if you test the rest of their properties you will often find
that you now have an electrolytic rectifier more than a capacitor.

That is not to say that all old electrolytic capacitors are bad. I recently
worked on an old Tek scope and the electrolytics with 1967 date codes were
perfectly good. However, electrolytics used in HP equipment of the same
vintage are almost always bad. I have some NOS capacitors that are fine, and
I just tossed a bunch that weren't.

I also worked on a 1992 fax machine recently. Every electrolytic cap was
leaking, both physically and electrically.

Test your old caps. Ramp them up to rated voltage while watching the
leakage. Don't overlook ESR. If they are good, keep them and use them. If
they are bad, toss them. I wouldn't put much faith in the reforming myth,
though.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Hello Watson,


Nah. I have some 40+ year old radios where the electrolytic caps are
just fine. A couple times I actually did a resistor charge and leakage
test just to see. They were nearly as good as new.

Depends on a lot of factors including how long they have set without
being used, how long they have been used, how high a temp they have been
exposed to, etc. And of course how well they were made. The old timers
seem to be better made back then, and withstand the test of time better.
But the stuff being made today isn't as well made, IMHO. Smaller size,
les ofecerything, etc, means they don't last like they used to.

I just got thru replacing the main filter caps on two different HP PSes;
both were dead and gone. In one case the PS was 40+ yrs old, so it's
understandable. But 5 years is usually what they aim for. Hey, they're
full of juice, don'tcha know.

But sometimes when they had been in storage for decades they may have to
be "formatted" slowly to get them used to the job of "being a capacitor"
again.

That's reformed, as opposed to the original forming. And even so, you
may find that some of the juice has leaked, so you won't get the full
rated capacitance, but just a fraction.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Hi, Joerg. I do, literally, have some 40 year-old aluminum
electrolytics in my part bins.

What's the best way to "format" them?
www.vcomp.co.uk/tech_tips/reform_caps/reform_caps.htm

...Jim Thompson
--

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

"Watson A.Name - \"Watt Sun, the Dark Remover\""

wrote :


And that means what?

It means that if the cap you are going to use is that old, you had
better not assume that it has the rated capacitance at the rated
voltage. So measure it and find out for certain.

 

[Melissa]

I don't recall, I'd have to go look. I have boxes of them all over the
place in my lab, which still hasn't been unpacked since we moved.

Here, I have a huge case of these, for starters:
http://dimensional.com/~melissa/photos/Cap1500uf100v.JPG


--
Yours In Liberty, Melissa - Colorado, U.S.A.
http://melissasliberty.blogspot.com/

The last best hope for liberty, to give the world its first Bill of
Rights: http://www.UPAlliance.org/billofrights.htm