I have a client who called me in to look at his Xerox XC830 copier. When you turn the Machine ON, it starts spinning the internal feeding gears FOREVER, and that is all it does. Although the panel buttons seem to work fine (you can change the precentage of Zoom, select the nmber of copies...), but that is all - the internal motor still continues to spin forever, until you turn the machine OFF.
I believe that most copiers go through a Power On Self Test - well if this is what it is doing, for some reason it is not completing - it just keeps spinning the motor. Pressing "Start" does nothing.