Emax

Hi Emax Boffins,
Ever since a got my Emax it's produced a high pitch background noise
while it's on. This doesn't come through the audio outputs, so doesn't
effect its performance, but comes from the machine itself. It's not
very loud and sometimes I just mentally blank it out, but other times
it does get to me and is annoying.

Any one got any suggestions as to what it may be and how I might get
rid of it? I've put in a new power supply since getting the machine so
I don't think it's got anything to do with that.

Thanks for any advice,
Alan