A VTTC is a Vacuum Tube Tesla Coil and it uses vacuum tubes / valves for the oscillator that is self biasing from a grid leak circuit.


WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm


This is a quick lash up done in a few hours and thus is only working that good. It will properly be out of tune since the primary coil is not adjustable.


Tube 1x PL36 line output pentode
High voltage supply 230 / 2300VAC microwave oven transformer.
Supplied through a variac.
Primary coil 75 mm diameter, 0.8 mm diameter copper wire (0.5 mm2) 18 windings.
Capacitor tank 3x 10 nF / 2kV Panasonic ECWH capacitors in series.
Secondary coil 50 mm diameter, 200 mm long, 1430 windings, 0.127 mm enamelled copper wire
Topload Two bottoms from beer cans / none.
Resonant frequency Around 470 kHz. Higher without topload.
Grid leak circuit 15 windings feedback coil, 2,2 nF capacitor and 68k grid leak resistor.
Input power 100 to 200 Watt, not sure.
Spark length up to 50 mm long sparks.


The high voltage supply is not grounded.


15th June 2009

A quick lash up that uses a single microwave oven transformer as supply for a single PL36 line output pentode from a old CRT monitor.

The microwave oven transformer high voltage is rectified by a diode from a microwave oven.

The Panasonic ECWH capacitors for tank and grid leak comes from the high voltage power supply circuitry found in TV sets using flyback transformers.


Running in CW mode.



A fairly good output of 50 mm sparks for a coil that was put together without any complicated calculations done up front and without being able to be tuned. Primary coil was made according to a quick run through JAVATC to find the resonant frequency.

But despite that effort it still performed better without topload on that with, which indicates it was oscillating at a higher frequency than 470 kHz.


Further reading

http://stevehv.4hv.org/VTTCindex.htm Steve Ward have documented 5 of his VTTCs, the staccato controller and written a good FAQ that is a must for anyone wanting to build a VTTC.

http://drspark.org/ Christopher Hooper have documented 3 of his VTTCs.

http://www.mif.pg.gda.pl/homepages/frank/vs.html Vacuum tube database, almost any tube data sheet can be found here.

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