slight hum in turntable...A little advice please.

Hello all a quick question for you. I have noticed a slight hum in my Thorens TD-125 when the table is idle but selected as an input. The hum disappears when I touch the metal platter (I found that out by accident) and when I turn the table on and start the platter spinning the hum subsides to an almost inaudible level. Any ideas What may be causing this and what can I do to eliminate it?

By the way...The table was just restored so I don't think it's anything along those lines.Enter your text ...
sounds like a grounding issue. make sure all your connections are secure and in phase. 
You might try connecting a ground wire from the metal platter bearing support to the phono preamp ground terminal/lug.
Ground the chassis.

Your drive motor and/or power supply is leaking to ground?