Testing paper-in-oil capacitors

jim · 8th February 2003, 02:45 PM

Hi,

I've got a few NOS paper-oil capacitors.
Since I don't want to blow up my powertubes I
want to test the capacitors before soldering them in.
Is there a simple method to measure the leakage current.

Thanks

Jim

Sch3mat1c · 8th February 2003, 03:27 PM

What I do is hook it up to a 1-200V supply with a neon light in series. The rate at which the light flashes as compared to the capacitance is determined by the leakage current.
A typical old, sticky .1uF wax-paper type capacitor might go 1 flash every second, which is approx. equivalent to 2.2megs, IIRC. (You can test that by connecting a resistor in parallel with a good capacitor.)

This is safe up to about .5uF, where the pulses start getting dangerous to the light. A 0A3 tube should be used for anything larger.

Tim

8th February 2003, 02:45 PM	#1
jim diyAudio Member Join Date: Jan 2002 Location: Leopoldsburg - Belgium	Testing paper-in-oil capacitors Hi, I've got a few NOS paper-oil capacitors. Since I don't want to blow up my powertubes I want to test the capacitors before soldering them in. Is there a simple method to measure the leakage current. Thanks Jim

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8th February 2003, 03:27 PM	#2
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	What I do is hook it up to a 1-200V supply with a neon light in series. The rate at which the light flashes as compared to the capacitance is determined by the leakage current. A typical old, sticky .1uF wax-paper type capacitor might go 1 flash every second, which is approx. equivalent to 2.2megs, IIRC. (You can test that by connecting a resistor in parallel with a good capacitor.) This is safe up to about .5uF, where the pulses start getting dangerous to the light. A 0A3 tube should be used for anything larger. Tim