811A first light

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

Original poster: "James T by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jamest2000-at-att-dot-net>

Hi everyone,
 I am another vacume tube convert.
 I recently purchased a gizmo that had a RCA 811A and the associated
parts in a small metal case. There was a 2" diameter former with a
primary and grid windings on it. Inside the former was a small secondary
that could be rotated through 90 degrees. Both ends of the secondary
were brought out to the front panel. I had no idea what this could be.
 After some snooping I found the circuit was almost identical to the one
published by Carl Willis on his 811a page. So I removed the original
secondary and replaced it with a 1.5" X 7" tesla(style) secondary I had.
I worked! I got 3" brush discharge. Very hot. Melted the copper
secondary wire into a glowing orange ball. When I raised the primary
former up a bit, the output changed dramaticaly to mini sword like
sparks I have seen in the photos. I had lots of fun playing around...
until I got greedy.
 The wimpy HV transformer is current limited with a .001uf mica cap. So
of course I put another .001uf cap in parallel to boost the current.
Naturally the transformer instantly fried. Oh well, now I will bring out
the dusty MOT's I have.
 BTW the device turned out to be a cauterizing power supply for a
surgeons scalpel. This thing causes RF burns on purpose! I think the
freq. was around 30 MHZ before I changed it.
 Fortunatly I was able to rescue this circuit from it's mundane duty and
let it release the sparks it so longed to do.
 Thanks to the guys with tube schematics and such on their web sites.
I'm sure I spiked your hit counters.
Regards,
 James T