The problem is in the optics. If it happens when you first turn it on. It may be the ribbon cable not totally seated, or is damaged and needs replacing. Which in turn doesn't allow proper voltage to be read. Becareful when removing it and reinserting it. It is the ribbon from the main control board on the back to the ccd on the top. And if it happens when you make copies the optics v mirror may be catching on somethings due to it being bent or out of shape. Which in turn doesn't allow the optics to make a complete rotaion. Good Luck and sorry for my typing skills
Gen
February 2009