Lexmark C935 Series, Service Manual

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General information
1-13
5057-XXX
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Sensor (2nd transfer roll HP)
The sensor (2nd transfer roll HP) is used to detect the home position of the 2nd transfer roll assembly.
Printhead assembly
The printhead scans the four drum surface with four laser beams. It consists of four components: laser diode
(LD) card assembly, printhead motor, polygon mirror, and four start of scan card assemblies.
1. LD card assembly — generates a laser beam with the four LDs. The beam is turned on or off according to
a print data signal. The printhead contains 4 LD card assemblies for the colors CMY & K.
2. 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 laser beam in the drum axial direction. The laser beam reaches the
polygon mirror as it passes through multiple lenses, mirrors, and windows. The laser beam then arrives at
the drum surface.
3. 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
line.
When a laser beam is scanned across the drum surface from one end to the other while turning on and off the
beam, one line of latent image is created. If the scanning by the laser beam is repeated while rotating the drum,
a two-dimensional image is created. The resolution in the scanning direction (from right to left) is determined by
the rotational speed of the printhead motor, depending on how quickly the laser is adjusted. The resolution in the
process direction (from top to bottom) is determined by the rotational speed of the printhead motor. (The higher
the scanning speed becomes, the sooner the scanning of the next row can be started.)
Sensor (2nd transfer
roll retract HP)
2nd transfer
roll assembly
2nd transfer roll
retract motor
Transfer belt