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Building A VTTC

Original poster: "Cameron B. Prince" <cplists@xxxxxxxxxx>

Hi Miles,

I've had others recently email me with questions about building their own
VTTC like mine so I am copying this reply to the list to help them as well.

I have not started on my site and the how-to pages yet because I am still
tuning and tweaking. Last night I hit 36 inches 6 times. I decided that will
be my final target as it's twice the length of the secondary form. Once I
can hit this mark consistently, I will call the coil "wrung out" and build
the site.

I believe this is probably a record for a tube coil with a single tube and
so little power input. John Freau has the record for length at 38 inches,
but was running a 7,200V potential transformer at 30 or 60A. (Others, please
correct me if I am wrong here)

To get going now, I'd recommend you guys use Steve Ward's info available


Christopher Hooper also has a nice site here:


The primary difference between their coils and mine are:

1) Uses two matched MOTs with secondaries in series (watch your phasing on
the paralleled primaries - you will need a diode to handle this increase in
voltage - the MOT caps seem to be okay with double voltage as they don't
even get warm in my system)

2) Raised grid coil at 22 turns of #24 (I'm currently at about 5 inches and
I think this is going to be optimal)

3) Uses #28 on a 3.5 inch PVC form 18 inches long with 17 inches of winding.
(I've tried different sizes of wire, different form diameters and lengths,
but none work as well as this.)

4) Use a 6 inch primary with #10 or #12 stranded with thick insulation (I
use 600V PVC covered which is very thick - I've tried solid wire and wire
with thinner insulation and there seems to be something about the primary
going higher up the form due to thicker insulation.)

5) Use a 2500pF or 2700pF grid leak cap with at least 10k resistor. (I am
now using two 10k 300W rheostats in series as I find about 12k is optimal -
The 300W is overkill, you can easily get by with 100W)

6) I don't use the parasitic filter between the tube plate and the tank cap.
(I may put that in later, but I don't believe it is an absolute must)

7) If at all possible, use a large mica cap in the tank. The strontium
nitrates (doorknobs) are prone to heat up and just don't seem to perform as
well as the micas.

I hope this helps you. Please let us know about your progress and don't
hesitate to contact me if you have other questions.


> -----Original Message-----
> From: miles waldron [mailto:mileswaldron@xxxxxxxxxxx]
> Sent: Sunday, August 20, 2006 8:45 PM
> To: cplists@xxxxxxxxxx
> Subject: beautiful PICS
> Cameron,
> I read your thread on the pupman list. I believe a have 833A's and proper
> filament transformers. Can you point me in a direction to start building
> my own VTTC? I need some kind of a vague schematic.
> Sincerely,
> Miles Waldron