Lexmark C520 Series, Service Manual

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General information
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Duplex drive
The duplex motor is mounted on the front door assembly. Drive is provided to three drive shafts in the duplexer
by a belt that is driven by the motor. The drive shafts move the print media through the duplex unit during
printing.
Paper sensing
Sensors are strategically placed in the printer to ensure that the print media is making it to specific points within
a given time in the EP process. There are two paper flags; one at the bottom of the machine (paper pick) to
detect input paper, including duplex second side, from all sources and one at the top (paper exit) to detect paper
movement beyond the fuser. The flags are similar in design, in that a mechanical arm is moved by the media to
interrupt an optical sensor; both are normally blocked when no media is present. There is also a multifunction
transparency sensor that detects if: 1) tray 1 is present, 2) narrow media is being used, and 3) the media is a
transparency. The sensor works for tray 1, tray 2 (500-sheet option), and the MPF.
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