If you get no sound at all check the following. What plug is at the end of the lead from the Beogram. There should be the red one, a white one and an earth. Most Beograms have a DIN plug but a few, the RX I think beingb one, had RCA plugs so that it could be used with non B&O amplifiers.
Check the input you are plugging the cable into. Is it the dedicated Phono input? have you selected the correct input on the amplifier?
If all this is correct, try plugging it into a different input that you know works - the CD input for instance. Do you get any sound then? If you do it will be very quiet and tinny.
Report back!
Was it a Soundsmith SMMC4 or was it a second hand MMC4?