[NostalgiaRadioTime]

Thanks for your ideas. There's nothing new in the house to cause the crackling, as none of my other radios do it. I neglected to mention I did try several different tubes in each socket so I eliminated that possibility. However when I pulled the chassis, I heard something rattle within the tuner. So I turned the chassis upside down and out popped a fossilized black piece of grommet. I wiggled on the tuning capacitor and sure enough it's loose. So I spent the night making a wiring diagram (7 wires to the tuner and 2 to the light bulb) and will remove the tuner tomorrow and replace the grommets. While I have it out I'm going to run it through my ultrasonic cleaner. I can see the mica trimmers are very dirty and there's still a lot of dirt within the tuner itself. The one mystery I have yet to solve is how to remove the dial scale from the tuner. I see a set screw but there must be something else holding it to the shaft.