Hello Rok,
pin 7 isn´t the heater, it´s the cathode. Of course 22 volts there is far to high. Is there any DC at pin 8 (grid1)?
The tube is not gettig so hot because of overheating but due to a wrong bias!
So the current of the anode gets too high, hence the reduced voltage there.
The second reason of course being a defective tube. -> replace it.
pin 7 isn´t the heater, it´s the cathode. Of course 22 volts there is far to high. Is there any DC at pin 8 (grid1)?
The tube is not gettig so hot because of overheating but due to a wrong bias!
So the current of the anode gets too high, hence the reduced voltage there.
The second reason of course being a defective tube. -> replace it.
Achim
