Delta88 1985, seatbelt light always on

Hi When I got my car, all the lights and the chimes and the radio used to work fine. Then one day, the radio stopped working. Also the chimes to indicate that the head lights are on and the door is open, they stopped working, i.e. all sound from the car was cut off. Also the "Fasten Seatbelts" sign always remains ON. Are these Audio and the Seatbelts sign related. How can I fix them. My car is pretty old with 135/235?K when I got it. Thanks Ravi