813 tube coil

From:  Scott MacGregor [SMTP:smacgregor-at-aasp-dot-net]
Sent:  Monday, June 01, 1998 9:40 AM
To:  Tesla List
Subject:  Re: 813 tube coil

Tesla List wrote:
> ----------
> From:  Alan Sharp [SMTP:AlanSharp-at-compuserve-dot-com]
> Sent:  Saturday, May 30, 1998 5:46 PM
> To:  Tesla List
> Subject:  813 tube coil
> Greetings All,
> At the UK Teslathon I bought a couple of 813 valves -
> Has anyone used these for a tube coil? - is there a good
> schematic out there?
> I've never used tubes before - I think they need a heater -
> will a bunsen burner be all right :)
> I have checked out the specs 2.5kV, at 225mA - so in
> theory a pair of these - and a 2.2kV microwave transformer
> and I should be able to shoot for 1kw power output.
> But they are  pentodes (and I only understand triodes)
> The filament needs 10V at 5A - can I simply connect
> a 5-0-5V transformer or do I need to have a way of
> adjusting and correcting the current?

You provide 10V to the pins, and the filament resistance will limit the
current to 5 amps. A good way to increase the life of your tubes would
be to use a 5 amp variac to provide heater power. Increase the voltage
to the tube slowly till you reach 10 volts. This prevents "shocking" the
filament with a sudden inrush of current.  

> Hints, tips, help greatly appreciated.
> Have fun,
> Alan Sharp UK


Scott MacGregor EES,Co.
Enterprise Engineering Services Co.
E-mail smacgregor-at-aasp-dot-net
Member: Cable Television Advisory Committee, Plainville, MA