I found some old notes and a short video of a quick lash up vacuum tube tesla coil I made in a single day. I …
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.
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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.
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://www.mif.pg.gda.pl/homepages/frank/vs.html Vacuum tube database, almost any tube data sheet can be found here.