The first step in a Tesla coil is the transformer. It is what generates the initial voltage increase from a piddling 120V that is produced by an outlet to the powerful kilo volt range. In the good old days of 10 years ago you could just waltz down to a neon sign shop and purchase one of these, or, if you were more daring, head over to a business that had wronged you and steal the transformer for their neon sign.
Alas in this day of LED’s and solid state technology these transformers are being replace by smaller lighter and safer devices. The cost of this safety is that the transformers cannot be used to power Tesla coils. They have something called Ground Fault Interrupters that will shut the whole thing down if it detects a current spike, this is something you cannot get away from in a Tesla coil.
Still these heavy devices are not entirely extinct yet. If you shop around at neon sign stores they will occasionally have ones that were salvaged from other jobs. This is exactly how I got mine, I call him Bruno. Of course the gentleman who ran this particular shop insisted that I pay cash. This way when I inevitably electrocute myself, there is absolutely no evidence that we met.
It was with a small sinking feeling that I parted with 60$ cash and carried my new/used 12000V, 30 amp transformer home. So welcome to my project Bruno, the heart (or possibly lungs), of my Tesla coil.