Reforming Electrolytic Capacitors

Hello,
I got a bunch of NOS Phillips Axial electrolytic Capacitors, a lot of
They were stock from an electronics warehouse that closed. They were on a shelf for 30 to 20 years can be certain for sure.
The caps awere never used before.

I've read on capacitor reforming but it seems everyone does it a little bit different.

What is your approach and setup for capacitor reforming? any tips?

Should I reform and use this caps, or should I toss them out?

Thanks

I wouldn't use them anymore, though I see how it seems to be a pity to throw them away. I just wouldn't trust them in terms of reliability and even measuring them 'good' won't guarantee how they behave tomorrow.

Michael

Whoops said:

NOS Phillips Axial electrolytic Capacitors.
They were on a shelf for 30 to 20 years can be certain for sure.
The caps awere never used before.
I've read on capacitor reforming but it seems everyone does it a little bit different.
What is your approach and setup for capacitor reforming? any tips?
Should I reform and use this caps, or should I toss them out?

Click to expand...

if the capacitors are cheap and easily replaced, how valuable is your time to re-form?
I reformed a twist-lock electrolytic in a RCA BA-23a ten years ago.  It took nearly a day @ 5 mA to bring it up to maximum specified voltage.  That cap was made in the 1950's and the BA-23a is still functioning fine.

gridcurrent said:

if the capacitors are cheap and easily replaced, how valuable is your time to re-form?
I reformed a twist-lock electrolytic in a RCA BA-23a ten years ago.  It took nearly a day @ 5 mA to bring it up to maximum specified voltage.  That cap was made in the 1950's and the BA-23a is still functioning fine.

Click to expand...

Thanks
Time is not a problem
I'm just interested to know if the caps can still be used and the proper method to reform.

How did you perform the reform?

I would connect them to rated voltage through a large enough resistance to limit current to a few mA. High enough current to charge up despite typical leakage, but small enough current to limit internal heating.

I would be inclined to buy new capacitors, since replacing capacitors can damage PCB traces and you will be investing your time which has value.

JR

Gene Pink just recently had an example of his reforming device on display here.  You could certainly set up some sort of jig to reform multiples at once.  The wacky Western Electric collectors insist on reforming original 75 year old caps, and I don't find tales of people burning up their $10K vintage amps.....though they probably wouldn't admit it either! 

I always buy new caps when restoring or repairing equipment, I neve re-use used caps.

This situation is different since I have a nice quantity of Philips and other quality brands axial never used Caps (NOS).

I know that the process can take a long time, but I can leave it reforming while Im doing some other work.
it would be a shame to throw this guys in the Bin:



Could you share the methods you use on reforming?

Thank you so much

Especially axial caps. 

FWIW capacitors do not generally wear out from use, but typically lose electrolyte through bung seals over time. There will be some acceleration to aging from operation at elevated temperature inside gear, or high ripple current that increases the temps inside reservoir capacitors.

Since axial caps are getting scarce, you could probably sell them for more than they are worth (IMO not much).

JR

JohnRoberts said:

FWIW capacitors do not generally wear out from use, but typically lose electrolyte through bung seals over time. There will be some acceleration to aging from operation at elevated temperature inside gear, or high ripple current that increases the temps inside reservoir capacitors.

Since axial caps are getting scarce, you could probably sell them for more than they are worth (IMO not much).

JR

Click to expand...

Thank you so much John,
my mind is made up already that I will keep them and try to reform them.
Arranging the sales would be much more time consuming and boring to me than to learn and challenge me on something new.
Also those caps are really useful to me and I dont want to sell something that might not work.

Moving on...

If there's fellow members around with experience on reforming caps, I would love some of your tips

thank you

First measure capacitance as also ESR if you have an option, then think about "reforming them".
Many old electrolytics keeps specs as also wor without any problem.
Am using these axial Philips without any problem in many type of gear.

ln76d said:

First measure capacitance as also ESR if you have an option, then think about "reforming them".
Many old electrolytics keeps specs as also wor without any problem.
Am using these axial Philips without any problem in many type of gear.

Click to expand...

I can measure capacitance with my Fluke 179 meter , it measures from 1nf to 10.000uf

ESR I have a cheap chinese meter, it's not amazing but I can get some rough values, I'm never sure if I should trust it or not, but its what I have

http://hkbbs.leowood.net:88/mini_read.asp?id=9463898&page=1&property=0&ClassID=0

those Phillips caps are highly sought after for projects as they have wonderful sound when used in API, Neve type projects , if you toss them toss them this way,

maybe make a bed o nails burn in rack

here is a page from Gerald Weber's Tech Talk book>

Whoops said:

Thank you so much John,
my mind is made up already that I will keep them and try to reform them.
Arranging the sales would be much more time consuming and boring to me than to learn and challenge me on something new.
Also those caps are really useful to me and I dont want to sell something that might not work.

Moving on...

If there's fellow members around with experience on reforming caps, I would love some of your tips

thank you

Click to expand...

I already answered that... connect to their rated voltage through a large value resistance that will limit the current until they re-form in. If they eventually charge up to near full voltage ( tiny leakage current) they are OK. If they get stuck at fractions of the applied voltage they are not OK. Of course just because they form up, does not mean that they are good caps. You still need to confirm their capacitance and ESR. 

I almost reformed a decent sized batch of caps back last century at Peavey when there was a cache of 15-20 YO capacitor inventory  uncovered (Hartley hates to throw away stuff),,, I had one of my techs put a few on the bench and they formed up OK, but i think I still ended up scrapping them... The cost savings from using old inventory did not compare to the potential liability from poor reliability performance... In business field failures are very expensive, and it is good practice to avoid them whenever possible, especially for only a few dollars worth of caps (probably not even worth the time I spent looking at them). We could buy new caps very inexpensively (you probably can too).

If you just want to have fun, get a PS and some resistors, don't be sensible just because I advised it.  My suggestion to sell them was tongue in cheek, because there are probably phools that would pay a premium for old anything.

JR

CJ said:

those Phillips caps are highly sought after for projects as they have wonderful sound when used in API, Neve type projects , if you toss them toss them this way,

maybe make a bed o nails burn in rack

here is a page from Gerald Weber's Tech Talk book>

Click to expand...

Thank you for the info, I really like the Gerald Weber books

JohnRoberts said:

connect to their rated voltage through a large value resistance that will limit the current until they re-form in. If they eventually charge up to near full voltage ( tiny leakage current) they are OK. If they get stuck at fractions of the applied voltage they are not OK. Of course just because they form up, does not mean that they are good caps. You still need to confirm their capacitance and ESR. 

Click to expand...

Thanks John, I will do that.
I will measure capacitance and ESR first.
And then make a Reform setup to see how it goes

Thanks

Whoops said:

my mind is made up already that I will keep them and try to reform them.

Click to expand...

I, for one, salute you.

How I go about it FWIW, is an amalgam of all those varying opinions that you have read, I likely have read the same ones to get started, and look forward to other's opinions here.

The basics being, a small current of a couple mA until you get a bit above rated voltage, and hold it there overnight. A good cap that didn't need reforming will get to full voltage quickly, hold it there overnight anyway, sometimes they develop shorts during this "test" and better to have it fail now, rather than a year later in use.

A large one that needs reforming may take a day or more to come up to rated voltage, once it does, hold it there for another day, as above.

For the smallish caps in your picture that I assume are all low voltage, I would suggest a current of about 1mA at zero cap volts to start charging, using a resistor in series with a supply set a bit above the rated voltage, will taper the current down nicely as the voltage increases at the cap.

Since you seem to have about a dozen of each type of cap, perhaps a dozen resistors, one for each cap, to do them all at the same time with one supply, but yet individually to monitor each one, per CJ's "bed of nails".

It is also a good idea to put them in a container while reforming, especially larger ones, in case they Napoleon*** on you.

The scariest reform I did was a dozen 2200 / 450V "tall-boy" 20 oz.beer can caps, all in parallel, in a 5 gallon plastic pail, lid clamped on securely. If one suddenly shorted, the other 11 would dump their energy into it. This was done out in the garage, where cleaning up the resulting shrapnel from a failure would be a lot easier.

*** Napoleon Blown-apart

FWIW,
Gene

since you have so many, you can cut like one from each group and see how much goop is left,

get some big dikes, like the red handled Klein Tools, cut in half, then squeeze with needle nose, put it on a cheeseburger and see what it does to the cheese, if it burns a hole in the cheese, then you are good to go,

won't work on an egg mcmuffin because those are already coated with electrolytes to preserve freshness,

have heard stories of companies putting lytics on slo-bake for a while, don't know what temp, certainly do not want to boil them dry,

looks like quad 8 used phillips also inside this diy job we just popped the lid on while checking on the input iron,>

Gene Pink said:

For the smallish caps in your picture that I assume are all low voltage, I would suggest a current of about 1mA at zero cap volts to start charging, using a resistor in series with a supply set a bit above the rated voltage, will taper the current down nicely as the voltage increases at the cap.

Click to expand...

Thank you Gene.

What does it mean "zero cap volts"?