01-19-2017, 05:53 PM
You might check the wirewound bias resistor marked 57 on the schematic. See if it is high in resistance.
Something is funny with your voltage readings. The bias voltage on the 42 grid is -24 volts, which would indicate that almost 100 mA is flowing through R57, which should be about 260 ohms total. Yet your B+ voltage is high and the 42 is conducting very little current, as the plate and screen voltages are almost equal (pin 3 and pin 2)l. Typically the plate will be about 10 to 15 V lower because of the voltage drop in the output transformer primary winding when passing the normal plate current.
Something is funny with your voltage readings. The bias voltage on the 42 grid is -24 volts, which would indicate that almost 100 mA is flowing through R57, which should be about 260 ohms total. Yet your B+ voltage is high and the 42 is conducting very little current, as the plate and screen voltages are almost equal (pin 3 and pin 2)l. Typically the plate will be about 10 to 15 V lower because of the voltage drop in the output transformer primary winding when passing the normal plate current.
