I am working on a DC coupled output cathode follower unit I found in the backwaters of Tube Cad Journal.
The 12BH7s seem to short somewhere resulting in an insane amount of current draw from the B- power supply. My ohm meter detects a low resistance from B- to ground after short trial runs. When the destroyed tube is removed, the resistance reads open again. New tubes read a high resistance as well meaning my circuit destroys 12BH7s. I have a feeling I am exceeding a rating somewhere, perhaps the cathode to heater. I probably could figure out the problem, but I do not want to sacrifice anymore tubes.
The filament supply uses a 7812 regulator. B+/B- are +/- 250V respectively.
Thanks all
The 12BH7s seem to short somewhere resulting in an insane amount of current draw from the B- power supply. My ohm meter detects a low resistance from B- to ground after short trial runs. When the destroyed tube is removed, the resistance reads open again. New tubes read a high resistance as well meaning my circuit destroys 12BH7s. I have a feeling I am exceeding a rating somewhere, perhaps the cathode to heater. I probably could figure out the problem, but I do not want to sacrifice anymore tubes.
The filament supply uses a 7812 regulator. B+/B- are +/- 250V respectively.
Thanks all