radio faults

[jagcat12]

On an 1990 v12 xjs the radio /cassette player which is a removable unit
and has the sockets built into the back and pushes onto the pins built into the car Anyway all of a sudden it has developed the following symtoms
When turned on it works to what ever station tuned to then after about 10 seconds start a loud beeping sound .Turning the radio off then on gets a repeat of the above.
This is not a code issue as have had battery disconnected also have removed from car on several occasions and always worked OK afterwards
I cannot see any mention of this fault in radio hand book Any ideas please


Dave