[TowerTalk] [Fwd: Re: Lubricating air variable capacitors]

[Barrie Smith]

> The LC-102 can also generate as much as a thousand volts for measurement
> of leakage current. So I put 1000VDC (the capacitor is rated for 3500
> volts) across the air variable and measured leakage current thru it. The
> value of leakage current varied ranged between 1 and 2 microamps as I
> turned the rotor.  Leakage current seemed to be slowly increasing as
> time passed. What is typical leakage current for this type of capacitor?
> What is the leakage path? Can the leadage be reduced/eliminated? Or,
> more to the point, should I be concerned with this level of leakage
> current? As a comparison, I had three other air variables (including two
> big transmitting air variables of the type used in Johnson KW
> Matchboxes) that measured zero leakage under the same test conditions.
>
> Advice?

As I mentioned in a previous post:  Is the capacitor clean?  Are any of the 
plates bent, or have nicks?

Spray it with "Simple Green", let it set for a few minutes, and then run it 
through the dishwasher a couple of times.  Let it dry completely and test it 
again.

1 to 2 microamps is way too much leakage for a 3500 volt cap.

Leakage should be measures with the plates fully engaged.

Leakage will increase considerably if there is dirt and grime on the plates 
or the end-caps.

73, Barrie, W7ALW