I wired a battery in series across the variable capacitor and found, indeed that it was shorting across the fins. It took quite a while, but managed to bend the guilty fin back into a position that solved the issue.
The radio works well, but I’m seeing low voltages throughout the radio and haven’t been able to diagnose the cause of this.
However, I’m particularly interested in finding out if anyone has any experience with the push button tuners on these old RCA radios. I followed the instructions to try to program each of the buttons to receive specific stations, but I’m having no luck. The radio isn’t responding at all as I adjust the cores and trimmers as instructed by the technical specs.
