Lexmark X746de Service Manual page 277

7526
Duplex drive
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The duplex drive is driven by the MPF/duplex motor through the MPF/duplex gear. Drive is provided to three
drive shafts in the duplex unit by a belt that is driven by the MPF/duplex motor. The drive shafts move the print
media through the duplex unit during printing.
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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 electrophotographic process. There are two paper flags: one at the bottom of the machine
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(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.
Paper pick sensor
Paper pick mechanism
Narrow media sensor
Input sensor
Diagnostic aids
3-79