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Re: My single 833A vttc -- first light!
Original poster: "BRIAN FOLEY" <ka1bbg@xxxxxxxxxxx>
Very nice! that is a nice picture as well. my camera hates arcs..cul brian
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
Sent: Wednesday, February 07, 2007 7:24 PM
Subject: My single 833A vttc -- first light!
> Original poster: Brett Miller <brmtesla2@xxxxxxxxx>
> My single 833A vttc had first light tonight..at least,
> first light with full power (due to the voltage
> doubler being installed).
> Performance was amazing, it easily started eating its
> own breakout point, which was a heavy (one of the
> larger ones) paperclip, straightened out and wrapped
> around a bolt which sits atop my John Freau toroid.
> You can see it happening in this picture:
> In that picture the coil is generating about 8"
> swordlike streamers into free air, however, I have
> video which shows some reach out to 14-15". I could
> possibly achieve an even greater distance once I set
> up a grounded target for the discharge. I may need to
> mount a tungsten breakout point atop that toroid as
> well. Something interesting I noticed, was that after
> the paperclip point melting into a sphere of molten
> metal the swordlike streamers began to appear in
> opposition and extend in various directions, with the
> curvature of the small metal sphere as the radiant.
> I have spent a lot of time tuning in the raw ac mode,
> and I arrived at a combination of primary tap, grid
> leak resistance, and feedback coil height, that seems
> to provide optimum output at least current demand from
> the mains. However, as John F. and others warned me,
> tuning a vttc is quite a challenge.....John, you sure
> said a mouthful there.
> Specs as of tonight:
> Single used 833A...label rubbed off (possibly RCA?)
> Plate transformer: Large MOT with shunts removed
> Voltage Doubler: 3 oven caps and one oven diode
> Filament supply: MOT with secondary cut off and
> rewound with AWG12....provides 10.7v at around 9.8+A
> at the filament pins
> Secondary: 19" winding length on 3.5" PVC former
> Primary: 28 turns AWG12 THHN, currently tapped at
> turn 21
> Feedback: 25 turns AWG23 magnet wire on slidable
> (coil did not oscillate at first...swapping these
> wires *did* promote oscillation in my coil) Currently
> the plate seems happier with the feedback coil about 2
> inches above the top of the primary.
> Grid leak system: 2 in series 3K Ohm 50W Ohmite power
> resistors in parallel with a single Yish 1.1nf 50kv
> doorknob cap
> Tank Cap: 2 Yish 1.1nf 50kv doorknob caps in parallel
> Topload: 1 John Freau 1.75" x 6" spun aluminum toroid
> Well, those are the specs I can think of...all grounds
> tied to a common point and connected to the same rf
> ground that gave great results in my 45" spark 12/60
> disruptive coil.
> I think I may have stated (at least to a few people)
> that I wasn't interested in getting competitive spark
> lengths here...but I think with some fine tuning (and
> staccato of course) I will be up in the 20"+ range.
> That would be extremely favorable.
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