813 tube coil

From:  Jim Lux [SMTP:jimlux-at-earthlink-dot-net]
Sent:  Monday, June 01, 1998 11:37 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

> 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?
Yes, you should have a way of adjusting the filament power. The
temperature of the filament affects the emission of electrons, which
changes the gain of the tube. More importantly, the temperature of the
filament affects the life of the tube.   This adjustment, though, can
probably be a "set and forget" type. Something as simple as a rheostat
in the primary of your transformer might do.

OTOH, if you don't really care about ekeing out the last percent of
performance or life, then hook em up with no controls. Just measure the
filament voltage at the socket to make sure it is within spec, and go
for it.