A number of options here. There is no DIN aux socket on the BV7 unfortunately.
If you still have the DIN cable for the beogram get yourself a DIN to RCA cable. On the right side of the BV7 there is a connection for a video camera or like. This is more of a temporary solution.
Alternately try an additional Scart to RCA connector which would allow you to connect the Turntable direct to a scart socket.
In either case you assign the socket to a command.
Do you have an audio system master linked?
Beoaus.