Lsp screens your optical leveling also make sure your not rolling the top pickup assembly roller and blipping the lock. As for the IBM's take your flashlight and look across the top of the relays at the wire contact potion sticking out of the top...see how many you have that have turned and fallen down inside of the relay thus making a n.o contact and n.c contact!! Now after you have checked all of them start looking across the bottom of the relays at the coil leads you will be surprised how many you find backed out....SE, U,D,UA,DA..