[Steve Davis]

Rich, let's go back to your voltages readings. The screen grid and the plate are both reading 323 volts, there is something wrong here. The plate should be a few volts less than the screen grid. The screen grid connects directly to the B+, but the plate is connected to B+ through the primary of the output transformer. There should always be a voltage drop across the the output transformer. Most likely cause would be a bad tube (low emission). Also, check the connection of the cathode to ground. Clean the tube pins and the socket. If someone has worked on your radio in the past, check the wiring, thp plate and the sg could somehow be connected together.

Steve