Re: Tube coil, level shifter madness

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

Original poster: "David Trimmell by way of Terry Fritz <twftesla-at-uswest-dot-net>" <davidt-at-pond-dot-net>

Hi John, Dave , all,

I guess I will come out from the woodwork ;-)

Let me recount my experience with Staccato and Level Shifted VTTC's, first 
I only use Level Shifting on my Vac coils, except for filtered DC.  The cap 
value does not seem super critical, but Dave's formula does help to get to 
that "optimum" value. My first experience (actually -Attempt) was not done 
very well. I was playing around with a big 6" coil with way too long leads 
(~24") and 2-3 833's powered by a beefy Plate Trany, getting only 8-10" 
snarly sparks. I then decided to try John's Staccato circuit using the 
74LS123's on this setup. Big mistake. I would get the Staccato board all in 
phase, hook it up and fire it all up, but would get Staccato control with 
low power short spark, only to have it die as I turned the Variac up. I 
replaced many burnt IC's, but eventually gave up. Obviously, I was getting 
a nasty RF field, that would clobber the sensitive IC's.
  Later, I had a much better research coil setup getting 19 to 20" sparks 
with two 833's (using Level shifting, of course). To this I installed a 
version of Dave Sharpe's 556 Staccato circuit, this worked great once I got 
it going (with much help from Dave!). I did not get any longer sparks than 
with Level Shifting alone, but could run at much reduced power consumption 
at low pulse rates. That sword like spark is quite cool to behold. But 
these beasts are quite finicky.
  I haven't done any VTTC stuff for a while, all that stuff is pack away, 
as I have been working on other projects. I guess I got a bit frustrated 
with my Audio Modulation work as it is also very "finicky". I was hoping 
some others would pick that up and improve (hint!), as much needs to be 
improved upon.  I think I will get back to some vac coiling soon, but 
haven't yet a goal (I work by goals), but meanwhile am working on some HeNe 
Laser stuff and playing around with a RM14S radiation detector I got, 
probably can even get a BF3 detector to work on this. Regrettably Fusor 
stuff is a bit too deep pocket for myself at this time...

So many projects...

Regards,

David Trimmell
www.ChaoticUniverse-dot-com

At 01:41 PM 1/1/01, you wrote:
>Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" 
><FutureT-at-aol-dot-com>
>
>Dave, all,
>
>Without staccato, I re-compared level shifter with the 2kV
>secondary vs. 3.6kV without level shifter.  The sparks are
>stronger with the level shifter as would be expected, since
>it's giving about 4kV, and better utilizing the xfrmer power.
>Regretfully, my original observation was made too hastily.
>
>Regarding the weaker staccato performance with the level shifter,
>I have some thoughts.  I had noticed in early
>staccato work using mechanical staccato, that RF
>envelopes which rose quickly, or were long in duration,
>tend to cause the sparks to branch.  This is not as important
>in steady (non-staccato) operation, since the sparks create
>a frenzied torch of spark activity anyway, along with quickly
>repeating ion trail re-ignitions.  However, for staccato
>operation, longest sparks are obtained with one straight
>sword-like spark.
>
>In earlier work with 24" level shifted staccato sparks, I was
>only able to obtain the straight sword-like unbranched
>sparks when using an MOT with the shunts removed.  This
>type of transformer tends to produce a very narrow RF
>envelope, with perhaps a slower rise time despite the
>level shifter.  I'm not sure if the rise time slows (compared to
>a normal xfrmer), but I know the RF envelope is narrow.  This
>combination of xfmer, level shifter, and coil design, gave
>excellent level shifted staccato sparks.
>
>It seems that as the power is increased, it becomes more
>difficult to maintain the straight sword-like sparks which are
>essential for maintaining the longest lengths during pulsed
>(staccato) operation.  My smaller (16") staccato coil uses an
>ordinary power transformer, not an MOT.
>
>Even without the level shifter, staccato sparks tend to
>be shorter than steady sparks, unless the sparks are
>straight and sword-like.  Tuning and other adjustments, as well
>as the coil's design, also tend to affect the type of sparks,
>making them more or less fuzzy, branched, or pointy.  My
>large 38" VTTC always gave fuzzy sparks, and this may have
>been affected by the poor Q of that secondary too (maybe).
>Work being done by solid state coilers will also be helpful in
>solving these kinds of questions.
>
>Regarding the operation of my TTL staccato controller, it
>seems to be triggering cleanly despite the addition of the
>level shifter, since this is still a small coil.  Higher RF power
>levels do tend to disrupt the TTL circuit.  When I added staccato
>capability to the large 38" tube coil, I was forced to use the 555
>timer based controller at the highest power levels.
>
>In conclusion, tube coils are critical beasts, especially when
>features such as level shifting with staccato, are added.  Best
>results require a careful combination of components, design,
>and adjustments.
>
>John Freau