Re: red 304TL

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

Original poster: "S Gaeta by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sgtporky-at-prodigy-dot-net>

Bingo!
I used .018 micro farad as the tank cap, and a grand total of 10 turns
tapped, and grounded at 4 for the grid coil, and 6 turns for the plate (this
is a Hartley osc.). When I look at other peoples circuits for similarly
powered coils, my values look absurd!
I will probably end up trying to cut the tank capacitor to no bigger than
.005uF. This will boost the number of turns required to produce the same
frequency, and it will probably be a lot closer to a reasonable inductance.

The fact that the inner turns (the grid portion) of my primary get warm
proves you are right. The temperature of the primary increased by quite a
bit as I increased coupling. I almost couldn't touch it when my friend had
it overcoupled to the point where the thing would suddenly drop out of
oscillation, and the tube would "play with itself" (his way of expressing
"thermal runaway"). We used my 3/4" copper tubing primary that I had built
for a larger disruptive coil! The fact that this large diameter conductor
got hot really scared me! The ground bolt at the bottom of the secondary got
hot enough to melt the solder on the lug, so I thought that inductive
heating was going on in the primary as well. There is probably a whole
plethora of bad effects happening here!

There was one really neat thing about this coil though. In the beginning , I
was using too large of a torroid (Bert H. straightened me out on that one).
Even though the streamers were short, the arcs I could draw off that torroid
were the hottest I have ever witnessed from any CW coil I have seen! The
power was obviously less distributed to output voltage, and more distributed
to RF current, and radiated power.

Demons???
Awww comon John, all tube coils have those! :-)

Sue
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, November 16, 2002 3:09 PM
Subject: Re: red 304TL


 > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<FutureT-at-aol-dot-com>
 >
 > In a message dated 11/15/02 11:14:49 PM Eastern Standard Time,
 > tesla-at-pupman-dot-com writes:
 >
 >
 > >. I used a flat spiral primary, which
 > >the tube coil experts tell me is a bad thing. I used the same basic
circuit
 > >with different component values for my 811A coil, which uses the
 > >conventional helical primary design, and it works fine, so the primary is
 > >probably the biggest problem with the 304TL coil.
 >
 >
 > Sue,
 >
 > I used a flat primary for my 36" spark tube coil and got good results.
 > However when I tried a flat primary on a smaller coil it worked
 > poorly.  I suspect the problem on the smaller coil was that I
 > installed the grid coil around the outside of the primary instead
 > of at the center.  The coil may have had other problems too.
 > That was the VT-27... a coil that was possessed by demons.
 > After doing an exorcism, I installed the flat primary into my
 > TT-42 TC where it remains today, and works well, demon-free.
 >
 > If a flat primary is used, be sure it has enough turns.  Primaries
 > with too few turns have probably ruined more tube coil projects
 > than anything else, especially at higher voltages.  (It's really
 > the inductance which you want to be high to give a suitable
 > load impedance to the tube.)
 >
 > John
 >
 > (just kidding about the demon thing    :)
 >