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Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
hello Dr. Spark do you think that Russian doorknobs would work the same as your mica's? do you think that those Russian tubes need to be water cooled or is air cooling plausible? I set my gu-39 up with a chimney and blower. Has your circulating current increased with he new primary and has it made your sparks longer. When I have seen vids of big VTTC's sparks seem to get more of them and more gnarly instead of more beautiful sword sparks. I was thinking that a H bridge could be used to drive the grid between cutoff and saturation on each cycle with a pickup from the primary as the feedback kind of like a drsstc front end driving the tube. The purpose of this would be to control the on time of tube and get rid of the Armstrong resister and capacitor on the grid. What does any body think
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Hmm, with a 10 turn primary the calculated capacitor would be up to 30nF on my coil, I think I would need one hell of a cap to stand those currents (iirc I calculated something like 170 amps rms).
teravolt: The GU39 is an air cooled tube, I would not mess with water cooling on it. The plate dissipation is up to 8 kW and in a well tuned oscillator, you can get output power 2-3X the plate rating.
Registered Member #1034
Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154
Jan, here is a link to a post I made that shows the evolution of my 833 style tube coil. It doesn't use a 833 tube but I call it that because the circuit is the same as a lot of 833 tube coils people build. I thought it might be of interest because it uses a relatively small primary capacitor. in the last picture you can see that it is about .001uf.
It's fairly small because the coil runs at a high frequency and there are about 35 turns in the primary. Just thought this might give you some ideas. Coincidentally the capacitors used here came from Dr Spark's stash. Henry sent them to me.
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
tradishionaly a primary for the armsrong oscilators that are popularly built hear use multipule turns so wouldn't less turns and fatter wire be better to increase the Q and circulating current? I want to make a test bead the will use multipule doorknob caps in parallel like Qadzilla to decreas ESR.
Registered Member #1034
Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154
In my case I experimented some with different primary turns to primary capacitance ratios and having the high number of turns in the primary works the best for my coil. I think it might have something to do with matching the impedance of the tube with the load of the circuit. Quadzilla on the other hand might be a totally different beast.
Registered Member #229
Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506
In a discussion with Mazzilli he said to me that every tube likes a specific number of primary turns/ plate voltage, so this can be experimented a bit for each tube to get the best value. I designed the GU5b VTTC after reading a few times the VTTC suggestions of James on tesla list LINK . Thats why I went with a low frequency secondary for this big tube. I wanted also to increase the primary cap value and decrease the number of primary turns (I run now a 2.95 nF cap), but I can't do more experiments because momentarily lack of power capacitors.
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Big VTTC ideas
