[Ron Ramirez]

Have all of the paper and electrolytic capacitors been replaced?

If not...replace them and then get back to us.

Sounds to me like a classic symptom of a paper cap that has gone bad; the trouble manifests itself after the radio plays a while. Sometimes it may come on and play with distortion right away, too.

This is why all of these must be replaced if you intend to use the radio.