Obvious question - are these systems well isolated with heavy duty line
conditioners - if so seems less likely noise is from building/equipment
electronic junk.
 
Second - I once experienced similar pathology with imaging boards. Examining
a grey wedge test image was very informative - turned out every fourth value
droped out/or was incorrect. Turned out specific bit(s) in image memory had
failed - which one became clear when converting to binary rep of the values.
 
Hope this helps
 
joel lowy
[log in to unmask]