05-04-2022, 02:52 PM
What are you calling the control grid on the tube? A 6A7 behaves like two tubes in one, with a common cathode. The control grid is the tube cap (G4 on the schematic.)
As far as the oscillator, have you checked the larger section of the coil? It could well have a turn or two that is corroded and shorting together or opening the circuit. G1 is your oscillator grid, while G2 acts as its plate with the coil forming a Hartley oscillator. G2 will have a higher DC voltage measured against the cathode. The only way that the control grid should have anything higher than about -6 VDC on it is if there is a shorted cap on the AVC line. Make sure that your oscillator coil doesn't have any resistive path across any two pins where there shouldn't be one.
As far as the oscillator, have you checked the larger section of the coil? It could well have a turn or two that is corroded and shorting together or opening the circuit. G1 is your oscillator grid, while G2 acts as its plate with the coil forming a Hartley oscillator. G2 will have a higher DC voltage measured against the cathode. The only way that the control grid should have anything higher than about -6 VDC on it is if there is a shorted cap on the AVC line. Make sure that your oscillator coil doesn't have any resistive path across any two pins where there shouldn't be one.
