Vacuum Tube Tesla Coil

This is one of my favourite Tesla Coils I currently have. It’s a valve-based Tesla Coil referred to as VTTC for Vacuum Tube. It is a very smooth operator, as the output is sinusoidal. Running here at less than 1kW producing about 45cm arcs. The lovely warm glow from the base is from the large Russian transmitter tube heater-cathode. It’s very stable and fairly bullet-proof, but the primary power supply is lethal as capable of 1A at about 4kV. The larger coil in the background is around 2 or 3 kW in operation and produces arcs of around 1m. It uses IGBT switching in H-bridge configuration on a 350V DC bus the same topology as an inverter. These can’t run in continual wave and need to be pulsed or the transistors tend to die. It’s very noisy and if I try to run it indoors even with 50V on the DC bus it will interfere with every bit of electronic in the house. There is a small battery TC on the bench which is safe enough to let kids play with. They are all good at running lamps wirelessly, as you can see with some tubes on the shelf above the coil.