We adopted the habit of soldering a 6-Amp rectifier diode across the posts inside the radio's power socket. The diode built into most radios is a "one-time" protector. It trips the fuse when polarity is reversed, but gets overloaded and shorts internally.
Back in the day, a slip-seat driver would have to play "Edison Roulette" with his gator clips to the posts on the doghouse of a tractor. The polarity marks had been rubbed off 200,000 miles ago, and if he guessed wrong the radio would be disabled, even if he had the right size fuse in line. A 6 Amp diode would happily pop a 2 Amp or 3 Amp fuse with no damage to the radio.
Makes me wonder if the protection diode in that model is a SMT part? Haven't looked inside one of those yet.
73