Vacuum tube Tesla coils (VTTCs) are not very common these days, but are still ranked very high in the overall coolness factor. Who doesn't like the electric glow of red hot filaments in strangely shaped glass vessels and a Tesla coil that is creating nearly silent 3 foot sword-like sparks. As part of today's daily blog, I am including free schematics and plans for a VTTC that uses dual high power 833A triode vacuum tubes. These tubes are monster sized tubes and when their filaments are powered up, they look downright mean and ready for business.
This design is relatively easy to build, especially compared to the newer DRSSTC Tesla coils, and can produce over 3 feet of output arc. It uses two 833A triode tubes, a common microwave oven transformer for the plate voltage source, and two mica capacitors for the primary tank capacitors. Finally, two 10V, 10A transformers are used to provide power to the tube filaments. The VTTC also uses one of our Staccato controllers to produce the sword-like arcs shown in the photos below.
Schematic and Plans
The links below provide the free schematic and datasheet for this dual 833A VTTC design. Original credit for this design goes to John Freau who developed this VTTC over 20 years ago. If you have any questions regarding the schematic or design, we would be happy to answer them. Contact us through our technical support page.
Click here for the dual 833A Vacuum Tube Tesla Coil schematic (PDF)
Click here for the 833A tube datasheet (PDF)
Staccato Controller for Sword-like Sparks
What is a Staccato controller? A staccato controller simply synchronizes the output pulse burst of the VTTC to the zero crossing of the input AC power waveform. When it does this, the vacuum tubes begin to switch at an initial lower voltage and as the AC sine wave begins increasing, the plate voltage will also increase. So the tubes will begin switching at some lower voltage, and through the pulse burst, which only occurs less than duration for a single 60Hz sine wave to peak, will switch at increasing higher voltage until the pulse burst sequence ends. This allows one to "shape" the RF output envelope and create sword-like output arcs. This is the same principle in which solid state QCW Tesla coils operate.
VTTC Staccato Controller Kit - Our popular VTTC stacatto controller kit allows one to create sword-like arcs with their vacuum tube Tesla coil.
Conclusion
Vacuum tube Tesla coils are really cool! Build one yourself. The dual 833A vacuum tube Tesla coil is definitely impressive and the perfect addition to any mad scientist's workshop!