[MrFixr55]

Hi OSanders,

I don't think that the 7A7 did damage unless the pins that are not used for a 7A4 / XXL are used as "terminal strips" and even there, I don't think that there is an issue. It is remotely possible that the radio would work with a 7A7 in place in the mixer stage but when I say remote, I mean remote.

Sounds like you are close. If you only got near to the tuning cap without touching anything and, lo and behold, the radio starts playing and stays playing when the wire and your hand are taken away, then somehow, stray capacitance started the oscillator.

Definitely check resistors and capacitors in the circuit, especially those in the cathode and plate of the oscillator. As a last resort, replace the various mica caps. These are the fixed caps between 100pF (100 mmF) and 330pF (330 mmF). These rarely fail compared to the electrolytic and wax paper / foil caps, but they are not failproof.

Also verify that the tuning cap frame is firmly grounded to the chassis at the factory ground point and that there is good continuity between the rotor shaft and the cap frame. There should be a spring contact. Do clean and lube the ball bearings that support the rotor shaft. after 80 some odd years, the grease could be dry and act as an insulator.

Hope this helps