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Old 12th Sep 2019, 1:01 am   #1
Sinewave
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Default Capacitor leakage tester

Since the best way to test capacitors is testing for leakage, I wonder if anyone here either has a good leakage tester for sale or some drawings for a good home brew leakage tester? Thanks.
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Old 12th Sep 2019, 1:53 am   #2
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Default Re: Capacitor leakage tester

From my notebook, here's a quickie design for testing high voltage capacitors at 100V and 200V using junk box parts. I later modified it to give an extra 50V range using the secondary centre tap. The "short" function is to discharge the capacitor after testing or reforming, only to be used with the meter off!
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Old 12th Sep 2019, 6:23 pm   #3
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Default Re: Capacitor leakage tester

Hi,

I built the same as discussed in this thread and it works really well:

https://www.vintage-radio.net/forum/....php?p=1077022

Also I might have a Heathkit IT-11 capacitor checker for sale, it's a very nice unit. It's a 110V but a step-down transformer comes with it.
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Old 12th Sep 2019, 7:32 pm   #4
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Default Re: Capacitor leakage tester

Quote:
Originally Posted by sven_swe View Post
Hi,

I built the same as discussed in this thread and it works really well:

https://www.vintage-radio.net/forum/....php?p=1077022

Also I might have a Heathkit IT-11 capacitor checker for sale, it's a very nice unit. It's a 110V but a step-down transformer comes with it.

I built a modified version of this tester, see post 10 of the thread. It's still working very well.

Peter
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Old 12th Sep 2019, 10:04 pm   #5
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Default Re: Capacitor leakage tester

Thanks guys, I shall take a good look.
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Old 13th Sep 2019, 3:01 pm   #6
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Default Re: Capacitor leakage tester

There's this one I built , see attached. I used my variac to get rid of the divider chain, the thing fitted into a 3" x 2" x 1" deep box. I use mine with one meter to monitor current, another voltage. As a good cap should have a linear dialetic resistance, if you put 350v on the CUT, you should see 35uA or similar leakage. Once used a few times you get a "feel" for a bad cap by the readings of the ammeter and voltmeter.

Andy.
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Old 13th Sep 2019, 3:12 pm   #7
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Default Re: Capacitor leakage tester

Quote:
Originally Posted by Diabolical Artificer View Post
There's this one I built , see attached. I used my variac to get rid of the divider chain, the thing fitted into a 3" x 2" x 1" deep box. I use mine with one meter to monitor current, another voltage. As a good cap should have a linear dialetic resistance, if you put 350v on the CUT, you should see 35uA or similar leakage. Once used a few times you get a "feel" for a bad cap by the readings of the ammeter and voltmeter.

Andy.
Thanks, will take a look into that.
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Old 13th Sep 2019, 7:35 pm   #8
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Default Re: Capacitor leakage tester

Two posts contravening forum rules deleted.
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Old 15th Sep 2019, 2:35 pm   #9
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Default Re: Capacitor leakage tester

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Two posts contravening forum rules deleted.
Sorry if that was me. If you let me know what it was I can make sure I don't make the same mistake again if it was my post. From memory I was responding to an 'item available post' in this thread.
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Old 15th Sep 2019, 2:46 pm   #10
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There was a political inference in them. We're very strict on this at this critical time.
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Old 15th Sep 2019, 4:02 pm   #11
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Default Re: Capacitor leakage tester

That's fine, thank you for letting me know.
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Old 17th Sep 2019, 6:41 pm   #12
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Default Re: Capacitor leakage tester

Quote:
Originally Posted by Diabolical Artificer View Post
There's this one I built , see attached. I used my variac to get rid of the divider chain, the thing fitted into a 3" x 2" x 1" deep box. I use mine with one meter to monitor current, another voltage. As a good cap should have a linear dialetic resistance, if you put 350v on the CUT, you should see 35uA or similar leakage. Once used a few times you get a "feel" for a bad cap by the readings of the ammeter and voltmeter.

Andy.
Did you still use a transformer? I'm not sure I have a 1:1 transformer here, I've got a load of others hanging around though.
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Old 17th Sep 2019, 9:21 pm   #13
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Default Re: Capacitor leakage tester

Hi, my homebrew design uses a small 0.5A variac and a 240/650v transformer, so can test up to 1000V and is isolated.
Metering on output and range switching for accuracy, also a dump circuit to discharge the cap at turn off , plus protection diode for the mA meter against reverse current when switching off.
2, charge resistors fitted, both quite high wattage so I can do a leakage test or run a reform cycle.

I'll post the circuit when I find it.

Ed
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Old 18th Sep 2019, 6:58 am   #14
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Default Re: Capacitor leakage tester

"Did you still use a transformer?" Variac and iso tfmr. "2, charge resistors fitted, both quite high wattage so I can do a leakage test or run a reform cycle" That's a good idea, the one in the "Big Bang" is ok for reforming HV low value caps, but not for high value low voltage caps, mind, I use a bench PSU for those.

Andy.
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Old 18th Sep 2019, 11:05 am   #15
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Default Re: Capacitor leakage tester

What's the maximum voltage and capacity you'd say this tester is fine for?
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Old 18th Sep 2019, 1:26 pm   #16
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Default Re: Capacitor leakage tester

With my variac 750v.

A.
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Old 18th Sep 2019, 2:09 pm   #17
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Default Re: Capacitor leakage tester

Hi Mine will go up to 1000v and capacitance is only limited by charging time. This could be adjusted with a change of series resistor value.
Also built into the case is an ESR meter.

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Old 18th Sep 2019, 2:47 pm   #18
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Default Re: Capacitor leakage tester

Thanks guys. This certainly sounds like something I need to build.
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Old 19th Sep 2019, 7:32 am   #19
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Default Re: Capacitor leakage tester

Here's a pic of mine.

A.
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