When you say "all channels",do you mean that the buzzing is still there on radio?Is it still there with the volume control set to minimum? If it's only when you play records,does the buzzing stop when you remove the record player  connector from the Beomaster? If it does,then the grounding connection inside the connector may have come adrift? There are two grounding connectors with B&O turntables,one to pin number two,and 'tother to the connector metal case. The plug comes apart,and the connectors can be checked and perhaps resoldered. Nick

Bad filter capacitors, perhaps? Martin

Thanks Martin appreciate the suggestion. I wish I had the technical nous to determine whether that's the case.