03-26-2013, 07:47 PM
Those plate and screen grid voltages are pretty close to spec. It could be that one of the resistors feeding that circuit have gone high, but the factory spec is 20V on the screen and 40 on the plate.
I suspect the last IF can (52), and one of the mica caps therein that form the output filtering for the detector. There is a pi network in there consisting of two 100pf caps and a 51K resistor, any of which might cause your problem.
BTW, there should be no signal on G2 or G3, they are AC bypassed to ground. Your output from that tube is actually the cathode (yes, at ground), where G1 and the cathode form the actual detector. The other side of the signal path is the bottom of the IF secondary, as seen on the schematic. This, as I said above, is inside the can and runs through that pi network filter before going to the volume control.
I suspect the last IF can (52), and one of the mica caps therein that form the output filtering for the detector. There is a pi network in there consisting of two 100pf caps and a 51K resistor, any of which might cause your problem.
BTW, there should be no signal on G2 or G3, they are AC bypassed to ground. Your output from that tube is actually the cathode (yes, at ground), where G1 and the cathode form the actual detector. The other side of the signal path is the bottom of the IF secondary, as seen on the schematic. This, as I said above, is inside the can and runs through that pi network filter before going to the volume control.
