Ideas? The original radio in my '64 chatters when it's cold. It's as if there's staccatto switch to the speaker. This happens when the ambient temperature is in the 40's (F). It happens whether the engine is on or off (switch in Run or Accessory), and the frequency does not change with engine speed, heater blower speed, or anything else I can find. It started this with the old speaker, and continues with a new one. So far I haven't found any loose contacts under the dash.
I suspect some component (resistor, capacitor, etc) in the radio is going out. Suggestions?