I was digging through my shed the other day and ran across my homemade HFAS unit. I will be posting some pics of the circuit and setup assembly within a week or so.
Building a HFAS unit was an interesting challenge because the voltages that are involved are way off the scale of most voltmeters. This makes it difficult to troubleshoot and figure out what is going on in the circuit. It was a learning experience, though, and I am quite pleased with the result. The unit works, but needs some fine tuning to make a nice smooth bead. I hope to get this thing working as good as the commercial versions and then offer a kit or plans for building your own.
There really isn't that much out there on the web regarding HFAS units, so hopefully this will contribute to the knowledge pool for those who are learning about this fascinating tool.
If someone out there can explain why the dual spark gaps are needed in the HFAS, I'd love to hear about it. I am still stumped by this one.
Commercial HFAS unit pics and schematic.
Bill the ArcStarter's HFAS design and info from an old book.