Lexmark T652 Service Manual page 528

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LD card assembly — This generates the laser beam. The beam is turned on or off according to a print data

signal coming from the system card.

Printhead motor/polygon mirror — The polygon mirror is mounted to the shaft of the printhead motor, and

is rotated at a high speed by the printhead motor. The mirror rotation shifts the incidence and reﬂection

angles of a laser beam to scan the photoconductor (drum) in a single direction. The laser beam reaches the

polygon mirror as it passes through multiple lenses, mirrors, and windows. The laser beam then arrives at

the photo conductor (drum) surface.

SOS card assembly —When a laser beam hits the SOS sensor on the SOS card assembly, the beam is

converted to an electrical signal (SOS signal), and detects the initial position where a scan starts on each

Polygon printhead

Appendix C: Theory of operation

T650 T656 T654