[Radioroslyn]

<Guess it burned the transformer? Think maybe it blew the caps in the power cord source..in the bake lite block?
Unlikely the power transformer bad from having the line cord shorted out. The two caps across the AC line are probably toast but they don't do anything anyway. But you should replace the filters in the power supply. If they short it will take out the transformer
<Where is best place to find this ,and the knob?
Well originally it had a 2 or 3 position switch for the tone control but what you can do is use a volume control pot and a .05mfd cap at 630v. This will
give you a variable tone control. Solder one end of the cap to pin 2 of the 42 (plate pin). Other end of the cap goes to one of the end terminals of the pot. Ground the center connection of the pot. That's it. The knob you can found on line as a repro.
GL
Terry