Search google for high frequency arc starter. Sorry I don't have any
links, there on my other computer that is currently down. However,
there are a couple of sites that show you how to build one. Also, look
up Tesla spark gaps, same thing same parts. HF is commonly used with
tig welding and also tesla coil people.

I only have experience with older welders and plasma cutters. This
means no solid state HF stuff. I'm no electronic expert, however I
have fixed three HF circuits (which really means I simply changed out
the capacitor). An HF circuit has basically three things: 1) step up
transformer, 2) high voltage capacitor, and 3) an air inductance coil.
The only thing that can really go wrong is that the capacitor goes bad.
It seems to be a common problem.

Test the capacitor (it will look like either a small hockey puck
(called a doorknob capacitor), or like a rectangular block about
..5"Wx2"Lx1"D. I buy mines off ebay for about $10 to $20 each). Again
search for high voltage capacitor or tesla.

Aloha, Russell