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Re: [TCML] 833A VTTC schematics
Carl,
The VTTC design is the standard one that's commonly used,
and works very well. It's very similar to Steve Ward's design, and
my own design. It's optimized for producing the longest sparks
for a given input power.
This style of voltage doubler is called an AC doubler or "lever shifter"
circuit. It's the same circuit as used in a microwave oven to double
the voltage to the magnetron. There's no need or benefit to using
a doubler having 2 diodes. A 120Hz ripple is bad for VTTC's, it
shortens the spark length and makes the coil draw excessive power.
The C5, and C7 cap values are OK as is. It's not desirable to use
filter caps unless one wants to modulate the VTTC with audio.
A filtered DC supply will make the sparks very short (unless a
circuit is included to pulse the coil).
http://futuret.110mb.com
Cheers,
John
-----Original Message-----
From: Carl Noggle <cn@xxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Thu, Nov 10, 2011 7:28 am
Subject: Re: [TCML] 833A VTTC schematics
Hi---
I checked out the schematic, and wondered how I could have missed a
voltage doubler circuit with only one diode. I simulated it in MicroCap
and found that it didn't work. It's missing a diode in the upper lead
from D1 to C7. That will form a half-wave voltage doubler, but I
suggest using a full-wave doubler as in:
http://www.google.com/imgres?q=full+wave+voltage+doubler&um=1&hl=en&safe=off&client=firefox-a&hs=0a3&sa=N&rls=org.mozilla:en-US:official&biw=1680&bih=909&tbm=isch&tbnid=yRKzukbRgcG8uM:&imgrefurl=http://sound.westhost.com/power-supplies.htm&docid=tvEHY89b4A2fxM&imgurl=http://sound.westhost.com/psu-f7.gif&w=640&h=220&ei=qWG7Ts3cA8qViALIooSHAg&zoom=1&iact=hc&vpx=623&vpy=165&dur=494&hovh=87&hovw=225&tx=188&ty=78&sig=106653913807423328229&page=1&tbnh=87&tbnw=225&start=0&ndsp=42&ved=1t:429,r:2,s:0
Why on earth do they need a URL that long?
Anyway, the full wave VD has a 120 Hz ripple frequency instead of 60 Hz
for the half-wave, making it smoother DC for the same filter cap. Caps
C5 and C7 should be a couple microfarads instead of nanos.
You might also look into reducing the size of the parasitic traps in the
plate leads.
Be sure to have adequate forced-air cooling of the tubes, especially the
seals.
Have fun. 833s are cool. No, they're hot. Well, you know what I mean.
---Carl
> I have acquired (2) 833As. I have looked at several VTTC schematics, I
> am leaning towards Dans
> http://www.easternvoltageresearch.com/resources/vttc833a_fullschematic.pdf
> This will be my 4th coil, but my 1st VTTC. Any advice,
> suggestions, or warnings would be welcome.
>
> Thanks Wm A Tickhill (aka Hairball)
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