I have an 84 Hurst Olds, the original Delco radio plays great but after 10-15 minutes I hear a pop and no more sound. Radio still lit and is on but no sound. After a few hours it plays again but only for 10-15 minutes.

 

Sounds as if a power transistor is overheating.

 

That’s what I’m thinking but don’t have a manual yet to see if there is anything external like a relay or if it even has an amp.

 

You could always remove the radio and test it with 12 VDC and another speaker. Hopefully someone has the factory manual and can help you.

 

The radio has an amp. It may be simply a power transistor which “amplifies” the audio signal in order to drive the speaker.

 

The factory radio/stereo is set for 10 ohm speakers so if someone has replaced them with aftermarket 4 ohm speakers the internal amplifier will overheat and shut off if you play it at higher volumes. Normal listening levels will be fine. But if, like me, you play Dio at maximum SPL, it won't hold up. If you are trying to get higher listening levels with newer speakers, you can add an aftermarket amplifier and use a high-power adaptor on the output of the factory unit. This will reduce the strain on the radio but still give you more volume than original.