Re: 18" sparks at 2KVA, 833a higher voltages

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: FutureT@xxxxxxx 

In a message dated 2/10/07 8:45:03 PM Eastern Standard Time, 
tesla@xxxxxxxxxx writes:

> Hi Cameron,
>
> John's site (futuret) has pictures of a (3) 833a VTTC sparking wildly
> powered by a 7500volt Pole pig. Tip: Bert Hickman told me there is a way to
> "ping" the tubes with a 10KV adj HV supply to increase their voltage
> tolerance.
>
> Jim Mora


Jim,

I tried that "spark knocking" or "debarnacling" method on some
833A's to try to increase their voltage handling capability.  It turns
out that the ones I tried had an internal spark gap section which
tended to arc at a relatively low voltage.  I think I tried some other tubes
also.  I used an HV supply that went up to 60kV or so.  In any
case I was not successful in raising the voltage standoff capabilities
of the tubes.  The HV supply I used was 60Hz AC.  I don't think
the desired arcing (slight "ticking") occurred while debarnacling
until I reached 35kV or more.

The 833A's can withstand somewhere from 5400VAC to
7200VAC depending on loading, plate redness, grid drive, etc.
I never run them over 5400VAC these days.  Some 833A's
can withstand more voltage than others.  Grid to filament
arcs are an ever-present danger too.  Debarnacling should
be able to help to prevent that also, I suppose.

John