18-06-2026, 10:53 AM
A small "wall wart" power supply with case removed will supply the power, and very cheap too. As to using the cathode bias for supply I can't see a problem if it is derived from a 5V1 Zener diode in series. That would give the output valve an easier life and still have the same current/voltage ratio for "auto bias" albeit with a lower standing current. We (well me) never use the full power of a radio anyway.
I want a PNP valve!
