This is a version of a Tesla coil where the primary is driven by a vacuum tube (valve) oscillator. “Continue reading” for more details and photos.
I have a Philips TB3/750 power triode rated at 3 kV 1 kW with a 5 V 14 A filament. The high voltage comes from a microwave oven transformer (MOT) and doubler. The filament supply is from a rewound microwave oven transformer to give the 5 V. This is largely a copy of Steve Ward’s vacuum tube Tesla coil modified to use parts I had on hand.
Above: Parts scrounged from my shed. I haven’t had to buy anything specifically for the coil at this stage. I was donated this and some other valves by Prof. David Blair (Physics, Uni of Western Australia).
Above: Steve Ward’s circuit diagram. The 833A valve is a bit more powerful then the one I have.
Above: The base of the vacuum tube Tesla coil. Left MOT is for the main HV with a diode voltage doubler using one of the 3 MO capacitors. Right MOT is the filament supply. Vacuum tube socket is front centre and MO suppression filters at rear for each of the two MOT’s.
Above: An early shot in action. This is not in tune and is only using a single 440 pf tank capacitor instead of the 5 I would need to get around 2000 pF (= 2 nF). This allows the rather small secondary coil to run with a relatively large toroid (the only one I have that looks decent close up).
Above: The tube glowing a bright orange. In this setup it is very inefficient.
A further step along the way. Still not in tune but with streamers up to 4 inches. Frequency is about 300 kHz but with a 2 MHz harmonic. I have a 12 inch secondary with about 750 turns of 26 G. No staccato yet but I have the parts.
Above: A thinking man’s ( err.. drinking man’s) toroid and some sword like streamers. Vacuum tube is not red (well, for short runs at least).
Now here’s a project. For a really big VTTC I have acquired a large 60 kW 30 Mhz transmitting triode that runs on 12 kV and has a filament current of 89 A.
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Photo dates 14/5/05, 6/7/06