RE: [TCML] VTTC-tuning. John got me started ;-)

["James" <mustang3@xxxxxxx>]

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Roger Smith
Sent: Wednesday, April 01, 2009 7:43 AM
To: Tesla Coil Mailing List
Subject: Re: [TCML] VTTC-tuning. John got me started ;-)

There is a VTTC on YouTube that is pretty big ( 
http://www.youtube.com/watch?v=7Ky4a9KPlVY )  .  It uses a 3CX3000 Tube
and 
runs at a fairly low frequency producing bushy looking sparks.  It seems

that most people prefer the sword like sparks these days and as I
understand 
it, that requires the coil to resonate above 300 KHz.


Some Snippage: Thanks for putting the link to my VTTC Roger. I have been
playing with the VTTC's since the 50's. I think they are lots of fun.
The effects are amazing. You can have an ion motor, light up lights
without wires, etc. The VTTC pictured in the link draws 80A at 240V. So,
I guess it would be one of the "big" ones. My favorite toob is the
304TL. I have tried 811's, 833's, 5868's and a few others. The tubes
with the carbon anodes are MUCH more robust. The 811's & 833's go gassy
very quickly if overheated.
	I certainly agree with John in the tuning. The VTTC are very
fiddly. Every adjustment effects all the other adjustments. I suppose it
is possible to tune the VTTC without an O'scope. However, it is easier
to tune with the scope. The feedback winding is always lots of fun. The
gridleak resistor and capacitor have to be chosen carefully. As an
example; the data sheet on the 3CX3000 toob shows that -500 volts will
put it into cutoff. I found that -3000 (minimum) volts is required for
smooth operation. The spectrum analyzer I use also helps in tuning. The
secondary "q" determines how much lower the primary frequency needs to
be. My VTTC starts at the primary frequency, then as the power is turned
up, it switches to the secondary fundamental (plus the freq splitting
effect). This effect is neat. The coil makes a cool click when this
happens.
     As for bushy vs swordlike, the discharge on my coil has always
looked like a gas flame. It's very hot, melting #10 copper wire in
seconds. Later, James       

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