All about the Roland Jupiter-series

Do the MKS-80 Super Jupiter VCOs distort easily?  I just got one so 
I'm a bit paranoid but...  I noticed the output of the synth appears 
to vary a little bit and I get some strange distortion when playing 
chords...  It's not distortion in my mixer, (I hear it through the 
headphone jack) and seems the H-M-L position and Volume slider 
position don't make much difference (though it's less apparent when 
the volume is lower).  So if anyone has experienced anything like 
this and can help me set aside my fears please offer feedback.  Oh, 
and I've been geeking out with today and it's been on for about 12 
hours straight, could have something to do with it?

thanks a ton,
ryan