Yamaha CS80

I was wandering,
My CS80's do have some noise/hum in their output signals. It's a 
little bit more then my other analogue synths.
I noticed the hum discreases when I plug the CS80 in an un-earthed 
socket-outlet. So that's what I do for some years now, without any 
problems. Maybe my other equipment is causing groundloops.
- by the way, I plug my jupiter 8's in un-earthed sockets too. If I 
don't I can hear some digital noise in their outputs -

How is this with other CS80's ? Are yours completely silent? What 
did you do to minimize this ? Can the hum be elimintaed completely 
by renewing PSU caps (I believe the caps in my psu's have been 
partly or completely renewed by my tech).

I also notice some "bleeding" of the voices when I don't play a key.

The bleeding and hum is still very acceptable, but I'm curious if it 
can be improved. I replaced all dual opamps allready a year ago.

I can give you some advise myself: keep audio-cables away from power-
cables since this reduces hum.