I’ll gear up to post all my schematics on tube power supplies and such, but I just want to mention one amazing part:
PTC (Positive Temperature Coefficient)
I use these, AND a traditional fuse on the 104V power supply line of the Phantastron. What’s so cool is that they protect you and your gear, but ALSO protect against stupid mistakes as well. (we all make them). The PTC in the Phantastron shuts the flow of electricity when current exceeds 50 ma. That allows the tubes to have more than enough power, but prevents a dangerous shock from getting through.
Furthermore, to "white-box" test, I hooked up the 104V supply to some tube heaters (usually the best way to hurt a tube and a power supply). The PTC kicked in and the current reduced to nothing in a blink.
Of course, if there is a fast surge I also have a 100mA fuse that completely cuts off the supply on the phantastron. However, in all my fiddling, I have yet to blow a fuse due to the PTC.
The best part: after power is removed, just wait 30 seconds and everything is perfectly normal again – the PTC resets!
Lorin