[Amps] Vacuum variable hipotting

[John Lyles]

Yes, you aren't really cooking the vacuum, you are 'spark knocking' the device. By applying controlled HV, the pesky whiskers that tend to cause sparkovers inside the device will be emitting electrons, cold emission from the enhanced electric field around the sharp point. The current flow from the power supply with dump some power in these points and they burn away. Or they get blown away from sparkover if the energy is high enough. This is essentially how a high potter can improve a vacuum device, not by sitting there at zero leakage, but when the leakage is showing, its working. Over time, the leakage should diminish and the voltage is then increased again, still within the ratings of the part. If the voltage is high enough, typically over 10 kV, weak X-rays may start being measurable. On higher voltage big tubes, they become quite objectionable, and require safety practices such as shielding. I have observed tetrodes drawing several mA at 50 kV and generating copious X-rays,
without even having filament connected. If the leakage doesn't drop over time, then one might suspect the vacuum having a small leak, or a major sharp point inside that cannot be cleared off. Or just dirty ceramic or glass insulation. 

73
John 
K5PRO

Message: 6
Date: Fri, 18 Sep 2009 11:17:31 -0500
From: donroden at hiwaay.net
Subject: Re: [Amps] Vacuum variable hipot

Can you "really" cook a vacuum ??
I have never heard of a getter function being available.
Don WA4NPL

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Message: 7
Date: Fri, 18 Sep 2009 13:09:49 -0400
From: "Carl" <km1h at jeremy.mv.com>
Subject: Re: [Amps] Vacuum variable hipot
To: <donroden at hiwaay.net>, <amps at contesting.com>
Its something to do with zapping off whiskers iff'n I recall correctly.
Similar to what Eimac does with "real tubes"

Carl
KM1H