Well, I finally gave up and had a seasoned RV repair guy take a look at my Airstream to assist in finding the Univolt and the 12 volt
fuses ... and, lo and behold, the reason I could not find either one is because ... they no longer exist! Apparently the former owner had replaced the OEM Univolt and 12 volt
fuse panel with a new inverter and bi-metal circuit breakers. His opinion is that what I have is much, much better than the OEM setup; he was also able to remedy the power problem to the radio, which was a loose retaining nut on the positive wire on the circuit breaker.
Again, I thank all on this forum who offered assistance and advice. I am now enjoying my new AM/FM/CD unit with an AUX input for an IPOD/MP3 player or other device. I can even rig up a cable from my DVD player and watch movies with the sound coming from the Airstream speakers! While the old OEM speakers sound great with the new unit, I may try replacing the old speakers with new speakers of the same size to get even better sound.