Belt Unit; Belt Up/Down - Lexmark C920 Service Manual

Belt unit

The transfer belt acts as a transport for the paper as it is carried from the registration rollers, underneath the
photoconductor drums, and finally to the fuser.
The paper is held to the belt by an electrostatic charge that is applied by a charge roller located inside the
transfer belt.
Once the image has been transferred to the paper, the transfer belt carries the paper to the separation fingers,
where the paper is detached from the belt and then enters the fuser.
Note: Besides acting as a paper transport, the transfer belt rotates during calibration to automatically
adjust the density and printer alignment. The density sensor is positioned facing the left side of the belt
where the belt drive roller is located. This sensor reads small patches of toner that are laid down on the belt
during calibration. To keep this sensor clean, a mechanism cleans the sensor surface when the front door
is open and closed.
Note: Adjust the printer alignment whenever the belt unit is replaced or removed. Furthermore, if the
transfer belt is damaged, toner can cling to the belt and contaminate the paper. When fingerprints or other
stains appear on the belt, wipe them away with a dry cloth.

Belt up/down

In monochrome printing, switching to color printing is not required. To avoid unnecessary wear of the
photosensitive drum by the cleaning blade, this operation is stopped with the electromagnetic clutch in drive 1.
The transfer belt is lowered so as not to touch the photosensitive drum during color printing.
The transfer belt moves up and down with the switching shaft cam by the electromagnetic clutch in drive 1. The
belt position is used to detect the cam position with the photo sensor, using the fan-shaped light-blocking plate
attached to the switching shaft. Printing with the transfer belt lowered is called monochrome mode, and color
printing is called color mode.
5056-XXX
3-31
Diagnostic aids