First VTTC light, and a few questions

["Grayson B Dietrich" <electrofire-at-juno-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Heyas, All!

For just about as long as I've been building spark gap coils, I've wanted
to build a vacuum tube based coil...  ...and now I finally have a
functional one!

Following equations in Duane Bylund's "Modern Tesla Coil Design Theory"
(a book that took me a year[!] of waiting to recieve-very unreliable
publisher) I wired up a coil with a single 811A triode. 

At first it barely gave the tiniest spark, but with quite a lot of
fiddling, rearrangement, and finally adding metering of  filament
voltage, plate current, and grid voltage (the meter wired for grid
current seems to be nonfunctional :p ) It now runs smoothly, apparently
well within the specs of the tube.

The sparks are only 2" long at the very best, and I've read that an 811A
coil ought to be able to give twice that....   ....so here are the
pertinent specs as best I see them, and a request for advice.

(values measured)
Plate Voltage: 1030VAC
Current Draw: 120mA (I'd like to draw more, as the plates aren't even a
dull red yet, but I don't want to reduce the grid leak resistor much
more... it is already only 3K)
Grid Voltage: -120VDC
Filament Voltage: 6.6VAC (the meter reads a rising voltage as i increase
the variac controlling plate voltage...  ...when the coil was ill-behaved
it would increase to as much as 10V, now it only reaches 7V...what is
happening?)


Primary: 4" thin wall PVC form, PVC insulated #18 wire, 23turns, tapped
at 18, windings are 1 7/8" tall.
Feedback: on same form as primary, Cottenamel insulated #24 wire,
19turns, not tapped just wound on and off (excess spirals in solenoidal
forms to reduce space taken up)
Secondary: 3.5" dia. thick wall PVC, #28(a guess, worked right with
WinTesla) enamel insulated wire, 5.75" winding height.
Terminal: 2.25" aluminum ball with a 1" wood screw attached, pointing
strait up.

Bottom turn of secondary is even with top turn of primary (gave better
performance than with more coupling) Feedback winding is 3/4" below
primary. Originally this was above the primary, and the coil performance
was terrible, while the metered voltage and current values were all much
too high.

Grid Leak Resistor: 3K to 4K, on a 20K 25W rheostat.
Grid Leak Capacitor: 4000pF, 1600VDC PP film/foil (4 1000pF caps in
parallel)
Tank Capacitor: 1000pF, 3200VDC PP film/foil (mini MMC, 4 1000pF caps)

Plate voltage is variable, brought up slowly via variac.
There is no filtering,

and....    ....Oh, yeah. Just how long ought I to let this thing warm up
before I apply Plate Voltage? the filament gets orange-white in seconds,
and doesn't appear to get any brighter if I let it sit there for a while.


Also, is it acceptable to run an 811A with a dull-red glowing plate, or
to what extent is such a thing allowed?

Thanks for any input, and I hope to hear from all you tube coil gurus out
there. 

Thanks, 

Grayson Dietrich
http://www.electrophile.8m-dot-com

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