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ginetto61 8th March 2013 11:21 AM

Testing New Old Stock electrolytic caps
 
Hi !
often at electronic fairs they sell NOS industrial high grade caps
They seem just perfect to be used in power amps PS
Problem is to verify their conditions
What would be the best way and then the most practical way to do this ?
Sometimes I see top brand parts (Mallory, Cornell Dubilier, etc.) at unbelievable prices thinking how much they cost new
The same kind like the ones here I mean :drool:

http://www.go-gddq.com/upload/2006_0...8133714492.jpg

Thank you very much indeed
Kind regards,
gino

AndrewT 8th March 2013 11:38 AM

reform them and then measure leakage current.

If you have the equipment you can measure esr.

ginetto61 8th March 2013 12:18 PM

Quote:

Originally Posted by AndrewT (Post 3401380)
reform them and then measure leakage current.
If you have the equipment you can measure esr

Thank you very much for your reply
Could you tell me something more about the reforming and the leakage current measurements ?
Thanks a lot
Regards,
gino

Jsixis 21st March 2013 01:46 AM

I own a tube Eico capacitive checker and it reforms capacitors.
I mainly use it on NOS capacitors. I have reformed around 50 old capacitors.
I haven't reformed any newer capacitors nor anything over 100uf but from my experience, reformed capacitors work but they do not have near the power reserve of new capacitors.
(screwdriver short proves it :)

I needed a 8800uf @ 100 volt capacitors and bought 9 used caps like in your picture. The one I put in the amp works great and was really the only way I could afford it at that time.
Now, the prices and size has dropped so much I would go new, just depends what your looking for.

gmphadte 21st March 2013 05:38 AM

But the bigger ones sound better.

Gajanan Phadte

ginetto61 21st March 2013 06:49 AM

Quote:

Originally Posted by gmphadte (Post 3420317)
But the bigger ones sound better.
Gajanan Phadte

Hello ! could you elaborate a little more your statement ? :rolleyes:
Anyway i have the same feeling ... i like big caps indeed ;)
Regards,
gino

indianajo 21st March 2013 05:36 PM

If you like working on equipment, fine. If you like listening to it, don't buy anything over 20 years old. Most of these caps are rubber sealed aluminum bottles. How are your twenty year old beer cans? To really test, put in an environmental chamber at 140 deg F or so for a week, then check capacitance and ESR while hot. The ones with bad seals will have leaked out the water at the end of the test. Then after installation, remove and test once a month. Just like an old tire, just because holds air today, doesn't mean it will tomorrow. The exception is epoxy sealed caps, they are really long life. I don't know how to tell one by looking at it, without a datasheet listing that part number.
I use and restore old electronic equipment, but the old e-caps all go at the first sign of deteriorated sound. I do experiments with old e-caps, particularly the ones from VFD motor drives (very high service life from AB or TBWoods brand drives, **** from semi brand drives) but don't button them up in cases or anything permanent.

ginetto61 21st March 2013 06:41 PM

Thank you very much indeed.
I guess that some Manufacturers give an indicative shelf life ?
These ones should be among the best ,,,,

http://www.epcos.com/inf/20/30/db/aec_2011/B41554.pdf

and they mention a Shelf life up to 10 years
so I understand that 20 ys are indeed a lot
I will check and try to understand the production date
The good and big caps are very expensive indeed
Thanks again
Regards,
gino

gmphadte 2nd April 2013 10:40 AM

Quote:

Originally Posted by ginetto61 (Post 3420354)
Hello ! could you elaborate a little more your statement ? :rolleyes:
Anyway i have the same feeling ... i like big caps indeed ;)
Regards,
gino

This is the knowledge gained from DIYAUDIO site. I cannot point you to any specifics, but it is a fact.

Gajanan Phadte

ginetto61 2nd April 2013 04:19 PM

Quote:

Originally Posted by gmphadte (Post 3437724)
This is the knowledge gained from DIYAUDIO site.
I cannot point you to any specifics, but it is a fact.
Gajanan Phadte

Thanks and regards,
gino :)


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