Re: VTTC MOT doubler, is it safe?

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

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

filament power comes from a rewound MOT, and it is like 10.3v, I sorta tried
mucking with the feedback coil and when it was too short, the coil would
stop working,  Has anyone beside me used the 813?

Regards - Jim Mitchell
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, November 17, 2003 6:53 PM
Subject: Re: VTTC MOT doubler, is it safe?


 > Original poster: FutureT-at-aol-dot-com
 >
 > In a message dated 11/17/03 9:28:41 AM Eastern Standard Time,
 > tesla-at-pupman-dot-com writes:
 >
 > >I tried the doubler, much bushier thicker louder arcs, not too much
length
 > >increase, I noticed the plate getting a red spot after a short run
though, I
 > >am wondering why I only get 5-7" arcs when people talk of 19" and such,
my
 > >design is based on the 803 desing from www.chaoticuniverse-dot-com, and I
have
 > >the primary tapped at various points which I can change, would anyone
happen
 > >to have an 833 for sale?
 >
 >
 > Jim,
 >
 > You may need to use 2 or 3 MOT caps in the doubler circuit for best
 > results.  The design of your coil is almost exactly the same as my
 > coil design which gives the 19" sparks.   The 813 tube is almost as
 > powerful as the 833A provided it can withstand the doubler.  Be sure
 > you have at least 23 turns in the primary when the coil is tuned
 > properly for longest sparks.  The addition of the doubler should
 > cause a tremendous increase in spark length, so the fact that
 > your spark length did not indicates a problem somewhere.  When
 > the grids are tied together like that, fewer turns will be needed in
 > the grid feedback coil.  For example if you had 20 turns in use,
 > you may need only 10 turns.  Also, you can move the feedback
 > coil farther away from teh primary instead.  Even without the doubler
 > you should get about 12" sparks from the 813 tube.  Make sure
 > your filament voltage is about 10.5 volts.  A low voltage on the
 > filament is very bad and will reduce tube life and will result in
 > shorter sparks.  Measure the filament voltage directly at the tube
 > socket or the tube pins preferably.
 >
 > John
 >
 >
 >