Re: Grid R/C pulsing of a CW VTTC

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <cwillis-at-guilford.edu>


Hi David,

Sounds like your're doing some neat stuff these days...

I think you're right that there's no problems with using the sputter mode if
the coil is DC driven.  I used this method on a small 211 based coil a while
back to make squealing, thin strands of discharge (corresponding to a
high-frequency blocking action.) As I recall, the grid leak resistance used was
nearly 100 kOHM!  You can tune the RC to make different AF noises in the
discharge and different discharge effects.

For DC coils, this may be a way to affect "super staccato" action- using both a
cathode-grounding staccato circuit (maybe just an SCR switched by a signal
generator since no phasing issues occur) as well as a high grid RC for higher
frequency pulses within the main staccato pulse.  

In my experience, staccato control of my current (level-shifted, AC) 833-A coil
gave a slight spark-length and thickness improvement over sputter mode.  As
well as causing the sputter action, the high gridleak RC may adversely reduce
the actual oscillator conduction angle.  I never went into the mathematical
analysis of how blocking works, it was all experimental for me. 

-at-
Sent by: "Tesla list" <tesla-at-pupman-dot-com>
02/26/2001 03:07 PM MST

To: tesla-at-pupman-dot-com
cc: 
bcc: 
Subject: Grid R/C pulsing of a CW VTTC


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

Hi, I know several people have used the so called "sputter mode" (R/C time
constant, pseudo staccato) on AC fed VTTC's, but has anyone tried it on a
CW (filterd DC) coil? I ran a test with a single 304TL with filtered DC
and 3-6 uF cap with 50K ohm in the Grid leak, very interesting! It
produced gnarly 12+ inch staccato sounding sparks with only ~5 amps pull
from the mains. Unlike running with AC to the plates, you don't have the
phasing issues that tend to wreck havoc on componants. Just something else
to play with...

Regards,

David Trimmell