Paul, Can you please post the drive chip you are using for the steppers? I can't quite make out the part number. I think the 47uF caps should be as close to those chips as possible but would like to double check the datasheet.

Side note - I have a small contract job shop. 4 VMC's and a lathe. But my true love is building machines and controlling them. My user name is a left over from a long time ago in another forum, so I just use it now for easy remembering to me.