What causes the grid on a final output tube to go negative in respect to the cathode upon transmit and what would prevent this from happening?
The reason for my question is that I have a Regency Range Gain that will only key .75 watts and swing to 1.5 watts rather than the 1.6 watts swinging to 10 watts. It has been recapped, resistors checked, aligned and new tubes tried without success. Everything checks out except for the final tube voltage. As you can see on the included pic, the grid (Pin #2, V12 - 12BH7) should be at -16VDC during transmit and in my case the voltage remains positive and is about the same as the cathode; approximately 14VDC. I suspect this is my problem but I have had a very difficult time finding a good explanation on what in the circuit drives the voltage negative and why it isn't occurring in my case. Thank you for your help!
The reason for my question is that I have a Regency Range Gain that will only key .75 watts and swing to 1.5 watts rather than the 1.6 watts swinging to 10 watts. It has been recapped, resistors checked, aligned and new tubes tried without success. Everything checks out except for the final tube voltage. As you can see on the included pic, the grid (Pin #2, V12 - 12BH7) should be at -16VDC during transmit and in my case the voltage remains positive and is about the same as the cathode; approximately 14VDC. I suspect this is my problem but I have had a very difficult time finding a good explanation on what in the circuit drives the voltage negative and why it isn't occurring in my case. Thank you for your help!