Miniature Vacuum Tube Tesla Coil

by Mark S. Rzeszotarski, Ph.D.

Photo #1 (56Kb)

Vacuum tube tesla coils operate in a continuous wave mode of operation, continuously providing energy to the tesla coil secondary. As a result, the output is primarily determined by how much power the vacuum tube can process. The spark discharge and operation of these coils is quite different from disruptive coils. If a D.C. voltage is used to operate the coil, the spark breakout hisses, as opposed to the 60 cycle hum normally associated with an A.C. operated vacuum tube coil.

The following text and images describe a small vacuum tube tesla coil which uses a single 6146A or similar beam power vacuum tube. Other television horizontal amplifier tubes can be readily substituted if desired. The approximate power output is 35 watts, and the unit is capable of generating a brush discharge of approximately one inch in length. Normally, a small brass knob is attached to the top of the coil so that spark breakout is inhibited. In this case, considerable R.F. energy is generated, and luminous tubes (e.g., neon, argon, xenon filled gas tubes) can be readily ionized and caused to glow while held in the hand several feet away from the coil. This provides an opportunity for considerable study in a relatively safe operating environment, compared to most tesla coil systems.

Note that although this coil operates at 620 kilohertz, it is quite capable of causing severe R.F. burns, and electrocution is also possible due to the high voltages used in its operation. The information provided here is for educational purposes only. If you are not experienced in the construction of high voltage apparatus, do not attempt this project! Please also read the safety FAQ on tesla coils before you attempt to construct these devices.

Photo #2 (86 Kb) This tiny vacuum tube oscillator was constructed to evaluate and study several principles of tesla coil operation.

Copyright 1997
Mark S. Rzeszotarski, Ph.D.
Cleveland Ohio, U.S.A.
All Rights Reserved.

revised September 3, 1997 by