Dell 5100cn Color Laser Printer User Manual page 192

CAUTION: Do not touch inside the printer with your hands. Some parts may be hot. Allow time for the
printer to cool before attempting to remove parts in this area.
4. Gently wipe the automatic density control (CTD) sensor window with a clean dry cloth or cotton swab.
NOTE: Do not allow anything hard to come in contact with the automatic density control (CTD) sensor window. Do
not use excessive force to clean the window.
5. Replace the transfer roller. Grip the tabs as shown.
6. Align the arrow marks on the transfer roller to the marks on the printer, and gently push the roller into the printer.