Hi mate, if yours is the later type p38 it could be the amp. Common failure. If not it might be a condensation problem. The radios rarely fail, its normally caused by something else!
If you're getting a hiss out of the speakers then the unit or amp (depending on your system) might still be supplying power to the speakers. If you can vary the volume of the hiss then I'd have a look at your aerial connections.
