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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 7th Feb 2020, 1:17 pm   #21
geeoboeh2s
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Default Re: Old Capacitors.

A word of caution on relying on an ESR meter for checking very old electrolytic capacitors.
My normal way of checking an electrolytic capacitor is with a variable voltage power supply and series 10k ohm resistor. Monitor the current with an Avo gradually increasing to full working voltage or slightly above. If at any time the current reaches 1mA with no sign of decreasing the test is stopped and the capacitor consigned for re-stuffing, otherwise the test is continued to reform the capacitor.

Recently I purchased an ESR meter. I tested a capacitor labelled 4uF, 350Vwkg, dated Mar 1945. It wasn't labelled as such but I suspect this capacitor met RAF stores no. 10C/4950, a dry electrolytic. The ESR reading was 6.94uF, 0.83 ohm. It looked good.
However with a capacitor manufactured over 70 years ago I was not prepared to use it without a representative leakage test. Sure enough with only a few tens of volts applied the current measured several mA with no sign of decreasing.

I am not condemning the ESR meter for evaluating modern capacitors that are manufactured rather differently.

Chris
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Old 8th Feb 2020, 4:45 am   #22
Maarten
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Default Re: Old Capacitors.

The ESR meter would be equally useless on a modern leaky capacitor. Some paramaters should always be tested separately regardless of the age of the capacitor.

Also, the relatively high capacity value could indicate the oxide layer is too thin. In this case, reforming apparently didn't help, but it often does.
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Old 8th Feb 2020, 10:15 am   #23
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Default Re: Old Capacitors.

On the mentions above of good makes, we might want to consider Wurth.

Wurth are a German company, who got going in the inductor business (almost said 'field'!) and have a good reputation. They've recently started doing electrolytics. I'd expect Wurth to be careful and trustworthy. They're red coloured.

Of course, it'll be 3-20 years before the verdict is in on them, but I'm inclined to try them.

David
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Old 8th Feb 2020, 12:56 pm   #24
Maarten
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Default Re: Old Capacitors.

They bought a Chinese factory. They probably have good quality control, but I'll only use them as a second brand behind Panasonic.
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Old 8th Feb 2020, 1:13 pm   #25
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Default Re: Old Capacitors.

I worked in a garage where wurth supplied us with our sundries ie exhaust clamps jubilee clips and sprays etc, it was really cheap and nasty stuff so when we ran out we never re-ordered from them.
Looking at the prices and spec of wurth caps on rs components seems they are bargain basement stuff.

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Old 8th Feb 2020, 10:08 pm   #26
Maarten
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Default Re: Old Capacitors.

On the other hand, Panasonics are often overpriced at RS, unless you order 200 or 1000+ so the difference might be slightly smaller.

Still Wurth have no "native" knowledge of capacitors, they mostly bought that factory to become a one-stop supplier.

Last edited by Maarten; 8th Feb 2020 at 10:13 pm.
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Old 8th Feb 2020, 11:23 pm   #27
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Default Re: Old Capacitors.

I just hope that this isn't another cynical misuse of a brand by a parachuted-in businessman with profiteering in mind, and that Würth capacitors don't do a Duracell on us....
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Old 8th Feb 2020, 11:44 pm   #28
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Default Re: Old Capacitors.

Quote:
Originally Posted by poppydog View Post
I worked in a garage where wurth supplied us with our sundries ie exhaust clamps jubilee clips and sprays etc, it was really cheap and nasty stuff so when we ran out we never re-ordered from them.
Looking at the prices and spec of wurth caps on rs components seems they are bargain basement stuff.

poppydog
I think that's a different firm.

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Old 8th Feb 2020, 11:51 pm   #29
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Default Re: Old Capacitors.

The electronic side of wurth is a subsidiary of wurth, they have their hands in everything.
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