I don't know about the earth connection, as the thing was buzzing even when switched to the radio or tape input.
Maybe it's just coincidence, but I checked under the deck and changed the voltage dial to 240, as it was on 220. Also I put some dampening material underneath the unit in case it was vibrating on the table surface. There is still a hum coming from inside, but it's a lot less, and I can certainly live with it, especially as the sound is sooo good through the speakers and I know my baby is really an old dinosaur. I hope it lasts a bit longer. Is it worth getting the power transformer replaced? Perhaps it's not even possible.