It's fun to grab scrap parts and slap them together to see what happens, and when smoke happens I tend to learn more. Fortunately, blowing up scrap doesn't cost me much! And fuses are pretty cheap too
Hopefully over the next few months I'll get things going correctly. The same circuit can be used as the front end for a high voltage supply too, so once I figure out what my scrap parts can deal with I should be set for power supplies.
But I'd better order a large box of fuses...