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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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11th Jun 2019, 3:37 pm | #21 |
Nonode
Join Date: May 2007
Location: Preston, Lancashire, UK.
Posts: 2,510
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Re: Testing capacitors for electrical leakage
If the source of water is a result of decomposition of the paper rather than moisture ingress, why is that 'waxies' tend to degrade whereas hermetically-sealed paper 'block' capacitors stay good? Is it just that block capacitors are typically military-grade and all the materials used, including the paper, are to a superior standard?
Andy |
11th Jun 2019, 3:45 pm | #22 |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,086
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Re: Testing capacitors for electrical leakage
They don't. That fact is very strong evidence against the ingress idea.
But they are made to a higher standard so often stay good for longer. It is all about the quality of the paper. Look at books, you see the same thing. I have a valve data book that I bought new when I was a child and now the paper is almost like ash. But I have much older books by decades that are still pretty good. I also suspect that the decomposition is auto-catalytic so once they start to go the process speeds up. |
11th Jun 2019, 4:32 pm | #23 |
Dekatron
Join Date: Jan 2003
Location: Bradford on Avon, Wiltshire, UK.
Posts: 3,301
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Re: Testing capacitors for electrical leakage
I have a 250 volt Megger that I use to test capacitors for leakage. It works very well. the high voltage is current limited as well, so it will re-form some electrolytic caps too.
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"Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly." |
11th Jun 2019, 4:55 pm | #24 | |
Heptode
Join Date: Mar 2017
Location: Cedar Grove, Wisconsin, USA.
Posts: 823
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Re: Testing capacitors for electrical leakage
Quote:
I preliminary test every set I'm going to restore. Many times, restorers replace every component, only to find, the thing doesn't work at all after part replacement, where it worked somewhat before. More later, Gentlemen! Dave. |
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11th Jun 2019, 5:02 pm | #25 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
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Re: Testing capacitors for electrical leakage
An all to familiar story often repeated in the forums. I guess some people have no technical knowledge at all and assume that replacing all passive components will get a piece of equipment working. All too often it doesn't.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |