Original AM Radio Issue

[53Rick]

My '72 GMC has the original AM radio which was working fine until it suddenly stopped working one day while I was driving. The fuse in the fuse box is fine and has power. I checked what I could on the wiring diagram I have. Does anyone happen to know if there was originally an in-line fuse on the AM radios? I can't see one under the dash. Seems strange that it suddenly stopped working as if a fuse went bad. As far as I know, the radios for 1972 were not a tube type. Any assistance is appreciated, especially if it can be identified without taking it out of the dash. Thanks.