Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Other Topics => Topic started by: uki on December 22, 2021, 08:21:47 am
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Found this tester on youtube, look to be very nice!!
link:
Does it matter the cap voltage ratting, does it really work with high voltage rating caps?
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An analog meter makes a pretty good leak tester. Set the selector switch to highest ohms scale. Connect cap. The needle will quickly swing toward zero as the cap charges and then drift back to some high resistance reading. A good cap with low leakage will cause the needle stay at that high resistance reading but a leaky cap will cause the needle to drift back towards zero. The greater the leakage, the closer to zero the needle will drift.
This is one of those tests where the actual numbers are not as important as the action of the needle. Simpson 260, Triplett 630, and most any VTVM or electronic meter, make good leak testers.
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I did put this tester together in the breadboard, seen to work, electrolytic caps may take a few mins to the led go off.
Others goes off right the way if cap is good.
@Sluckey I did try the analog meter as you suggested with a cap(220/400v) previously checked with the tester, tester says bad, did wait about 5 mins, but the meter read some resistance. :dontknow: :think1: It did read 10 at 10x , how much resistance is good?
Another cap(220/100v) tester read good and analog meter read above 50 at 10x.
here is my analog meter
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how much resistance is good
it's sorta a "learned" thing.
Like Sluckey suggested, the needle should be steady, no bleeding. I typically want many thousands of ohms and no downward drift.
I can get a pretty good "sense" even with the modern digital meters. The meter will charge the cap to some "resistance" value, hopefully many tens of thousand ohms. remove the meter, wait a hour, then "spark" the cap. If it's a leaker, the spark will be pretty weak. Again, it's a "individual" taste thing.
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https://worldradiohistory.com/
https://worldradiohistory.com/Popular-Electronics-Guide.htm
https://worldradiohistory.com/Archive-Poptronics/50s/59/Pop-1959-12.pdf 10MB PDF
The original doubles-up about 350V DC. Considering the simplicity, that's fair for many tube-era caps. Thin film in 100V film-caps and many e-caps will be ruined.
It looks real dangerous. Out in the open it could be fatal. With only "Test Leads" exposed you can get 3 or 4 mA of shock, and GFI codes allow 5mA. However an unexpected or over-anticipated 3mA shock WILL startle you witless.
The 9V re-think is mildly interesting, but can't strain HV caps, so needs lots of sensitivity.
The way he is holding the cap "all hands on deck" at 4:05 is frightening.
Caps can leak two ways. Simple linear resistance, current proportional to voltage. Then a low voltage is OK if the current is sensitive. Or breakdown, low leakage to 300V and then huge leakage. (Also varies with temperature and moisture.)
If a cap is leaking it should be apparent in circuit, for most audio amplifiers. Also caps are mostly very cheap and better-made than ever. If in doubt, replace. If the new one is the wrong color, peel the skin off the old one, or print a wrapper on color printer.
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https://worldradiohistory.com/Archive-Poptronics/50s/59/Pop-1959-12.pdf 10MB PDF
Oh this is the original !! I was surprised to find out that the file is already in my hard drive.
I think maybe you gave me the link before.
The way he is holding the cap "all hands on deck" at 4:05 is frightening.
The same guy does actually have another video with the HV version, if that is what you are talking about!
Caps can leak two ways. Simple linear resistance, current proportional to voltage. Then a low voltage is OK if the current is sensitive. Or breakdown, low leakage to 300V and then huge leakage. (Also varies with temperature and moisture.)
Great info !! :thumbsup:
The 9V re-think is mildly interesting, but can't strain HV caps, so needs lots of sensitivity.
So definitely need a tester that can do HV?
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How does this type of capacitor tester compare to my Anatek ESR tester?
https://cdn.shopify.com/s/files/1/0915/6622/files/Blue_ESR_assembly_manual.pdf?v=1608155660