Re: VTTC MOT doubler, is it safe?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Mike Poulton <mpoulton-at-mtptech-dot-com> 

Mike Poulton Wrote:
 > Original poster: "Jim Mitchell" <Wrenchead-at-starband-dot-net>

 > Hi,
 > I recently completed my first VTTC, it uses an 813 tube and a MOT from a
 > 1200w microwave.  I am getting about 5-7" sparks from the breakout point
 > during good conditions, and I was wondering would it be at all possible to
 > overdrive this tube and use a doubler on my MOT?  The tube has a max 2200v
 > plate, and I am afraid if I put doubled MOT power into it, it will form a
 > fatal arc inside or somthing.  The tube has a graphite plate, so Im not too
 > worried about it melting or anything, but I am afraid of arcs
 > inside.  Also, I am not running the tube in optimum conditions, I have the
 > screen and control grid tied together, and the beam plate tied to ground,
 > should I change it so that the screen is tied to B+  by a resistor, will
 > this increase my output noticalbly?  If not, I am going to spend some big
 > bucks on a few 833's

Most MOT's seem to produce about 2000-2500V, which is already right at
the tupper limit for that tube. Doubling it will give 5-6kV, which is
far more than the tube was designed to take. I certainly wouldn't try
it. You should be able to max out the MOT's power handling
capabilities without voltage doubling. Take a look at the input power.
If you have high input power and are only getting 5-7" sparks, then
something is wrong.  More likely, it is not drawing much current
because the impedance of the coil is too high.  Try better coupling or
fewer primary turns.

-------------------------------------------------
Mike Poulton