Positive supply for the relays doesn't work as it is drawn ? ;-)Look close at the power supply schematic.
A quiz
What do you see that you often do not see in other power supplies?
Thx - not quite zero though. Reputable reference suggests c 500nA typ for triode with mu c 60. And suggests grid leak bias R c 5-10M. Whereas 200M would require c 5nA leakage to work and that seems a stretch?Valves in class A like this have zero grid current
The heater is supplied by a current source / regulator.Look close at the power supply schematic.
A quiz
What do you see that you often do not see in other power supplies?
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