From the sublime (866) to the insane: Tung Sol 7791A hydrogen diode. Current rating: is 8 peak/2 ave. amperes and 25000 peak inverse voltage. Filament eats 15 amperes @ 5 volts. At 20 amperes forward current (Way outside its ratings) the 7791A drops only about 20 volts. It’s not as big as you would think: approx. 15 cm high, base flange 11.5 cm diameter.