OSVTTC – Early Days

This will be my third coil, if I ever get it working !

As before with the Vacuum Tube Tesla coil, this project uses a very large radio transmitter valve in place of the spark gap in the standard coil. This time I am trying to drive it with a variable frequency oscillator, which can be “tuned” to the resonant frequency of the coils. It only uses two coils, the primary and secondary coil.¬†It is a far more complicated design and may never work, but you don’t know if you don’t try!

+++Primary Coil+++

25 Turns 2.5mm copper cable wound on a 15cm former.

+++Secondary Coil+++

1000 turns of 0.315mm enammelled copper wire on a
68mm pvc former.


Variable between 150 & 500kHz, 300v p-p output.

+++Power Supply+++

2.1kV 1300W Microwave oven transformer for the main tube plate supply
2.1kV 1300W Microwave oven transformer for the main tube screen grid supply
12v 12A Transformer for the main tube heater supply
240v + 6.3v Transformer for the oscillator and grid bias

+++Tank Capacitor+++

1880pF 20kV Ceramic capacitor rated at 60kVAr

+++Control Box+++

Standard line filter at input, earthed to supply ground
275v MOV across supply outputs
Variac power control
Input ‘Live’ and ‘Ready to fire’ warning lamps
Output voltage and current meters
Key operated safety switch
Two simultaneous press-to-fire buttons and a long extension lead !!

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