1952 Plymouth Cranbrook?

The radio in my newly purchased 1952 Plymouth Cranbrook is not producing any sound. All of the dials/lights/ons work on the radio and the car is in overall good condition with only 27,000 original miles on it. I have the original manual and it states to wait 20 minutes before using the radio...so my question is, do I have to wait 20 min with the car running to give it the "true" test of working/not working, or is there another way to determine if it is functional?