Tesla Coil Uses Vacuum Tube

What do you do when you find a 5 kW transmitting tube in your local electronics store? If you are [TannerTech], you build a vacuum tube tesla coil. This isn’t the usual little wimpy coil, but a big bad boy that would look at home in an old horror movie.

The first power up was a bit anticlimactic, although it was working, it wasn’t very spectacular other than the tube glowing brightly. A few adjustments and some mineral oil did the trick.

Honestly, the build details are a little sparse, but if you have any business building a coil this big it should be enough for you. Besides, you aren’t likely to have exactly the same components he uses anyway, so you are going to have to improvise. No offense, but this probably shouldn’t be your first high voltage project.

This isn’t the first vacuum tube coil design we’ve seen. In fact, a recent one had a clever inrush limiter circuit that might work with this one, too. Tubes are good at handling lots of power like this without being very hard to use and there is just something about the filament glow that we always enjoy.

If you want to start smaller, try using a bug zapper. If you are too lazy to wind your own coils, there’s always some automated help.

16 thoughts on “Tesla Coil Uses Vacuum Tube

    1. Is it a nuisance? yes
      Will it kill anyone other than the operator? probably not
      As for me, if I had a tube or two like that I would be in the market for a strong fishing boat to broadcast from

  1. Minor thing; the fans moved air in fpm, not fps.
    Mineral oil mixes nicely with water. While it is not hydroscopic I cannot say over time if that would ever become an issue. Under more constant use, the warmth ought to keep moisture at bay. Mineral oil is used on breadboards and if 2.5 or 5 TBLsp.per gal water, make dormant oil spray for fruit trees, summer and winter doses, respectively.
    Nice job. Now quantify things a wee bit, as if it were a prototype product.
    Then make a miniature one for your power ring. 😲

  2. One year the folks were treated to an 24″ tall jacob’s ladder for halloween, but I kept it behind the porch window. You could hear it, though. (I killed.it when noo e was.coming for candy.) A big van de graff I set behind the school bully knocked him flat as he copied someone’s history notes before chem class. Papers went flying!!! It shocked him as much that I was the one who did it… and laughed, as did with the closely watching class, who were a bit nervous about laughing at all. 200,000 & as a science club geek I knew its max setup distance of 2 ft. First time I like our new plastic chairs, w metal rivets.

  3. This is nice build but I think he can do better. I built a Vacuum tube coil in the late 80s around a 4CX250 tube and produced heavy arcs out to 13inches or so with 1250Vdc input.

    First, the primary tank coil should be 10 gauge or heavier. The circulating current is enormous at resonance.
    Second, those little disc capacitors have too much internal resistance to carry the circulating current. He could easily double his output with mica transmitting caps like these: https://www.ebay.com/itm/36-Transmitter-Transmitting-Mica-Box-Condensers-Capacitors/173276784880?hash=item285819e8f0:g:ODkAAOSw3Z9aw7xD

    Lastly, I think 455 kHz is a probably a harmonic of the true resonant frequency of the secondary. I suspect the fundamental is under 150 kHz

    All just opinion of course…

  4. Nice to see some still using vacuum tubes on TC’s. Not a whole lot of us left, but we are here. Interesting that he used a pretty big tube, but input power does not match what it is capable of. Also big everything does not mean always good performance. You can get great discharge lengths from smaller coils also. Build quality, proper components, and proper tuning is key to good performance. But for first time effort he did OK. Should have started with a much smaller tube/coil, would have been a bit simpler, and with tuning, at least same performance or even greater with good tuning. Still there is even with current input levels, can be changed to improve this in the future when he can. Also a very great way to improve performance, besides proper tuning is to add an interrupter/pulse circuit to a VTTC. Even adding this, proper tuning is again required for optimium performance. Here is a link to a small coil that I have recently finished. Was pretty long process to reach this. Just a single MOT for input power. I will be posting more details eventually on this link, still trying a few things occasionally. So anyway here is the video link, at up to 30″ currently. Have at few specs currently listed, more coming…


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