[TCML] 833A VTTC schematics
futuret at aol.com
Thu Nov 10 06:58:39 MST 2011
Tuning up VTTC's can be a time consuming process to get optimal
performance. The various adjustments tend to interact. If the tubes
get red while producing 8" sparks, then somethings not quite right.
In VTTC's it's important to keep enough primary turns (enough
inductance, to keep the impedance high enough. I always keep
the primary turns constant, and adjust the capacitance in the tank
circuit for tuning.
Here's an important tip: An easy way to get an idea if you need
more or less C in the tank, is to alter the toroid size on the tesla coil as a
temporary test procedure. If a smaller toroid improves the performance
(longer sparks, and tubes show less plate redness), then more tank
C is needed. If a larger toroid improves performance, then a smaller
tank C is needed. I wouldn't recommend altering the secondary turns
as a tuning method. It's not necessary to use real toroids for these
tests, any sort of round piece of metal can work if the edges are
somewhat rounded. Sometime I use the cover from a cookie tin
for example for these tests. I make a hole in the center so the
spark emitting spike can protrude through.
I have 1.75" x 6" spun aluminum toroids available if anyone needs
them for a VTTC project, ($74 (free shipping within the USA).
I also have some VTTC photos and information at my website.
From: Michael Mayer <mpmayer0416 at hotmail.com>
To: Tesla Coil Mailing List <tesla at pupman.com>
Sent: Thu, Nov 10, 2011 7:28 am
Subject: Re: [TCML] 833A VTTC schematics
I just finished building my first TC which happens to be 833A VTTC using Steve
Ward's design, which can be found at
There are a few things I'll comment on which you can take at face value and may
or may not find helpful.
1. kickback (Wow!), touching circuit ground causes painful RF burns - I think I
need to add a good earth-ground to the circuit
2. tube plate heats up red hot immediately after applying power, and the glass
envelope definitely needs a cooling fan
3. to combat the red hot plate problem, I am in the process of building Steve's
Staccato circuit which will then be added to the 833A filament via triac.
4. only produces 8 inch sparks - definitely needs some tuning. I have several
taps on the primary (tank) circuit, but I guess I need to alter the number of
turns on the secondary? As you can see on Steve's circuit he is able to get
22-inch sparks. I can't figure out why mine won't make longer sparks as I have
used all the same component values per the schematic.
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