Xerox Phaser 840, Service Manual

Page: 35 / 287

General Information 1 - 19
Caution
The actual position of some printer assemblies, such as the
printhead or the cap/wipe/purge assembly, cannot be ascertained
at all times. The printer records, in NVRAM, where it last
positioned such assemblies each time it moves them. If, after
power-down or a power interruption, the assemblies are manually
repositioned, the printer erroneously assumes that the assemblies
are in the position it last left them. This assumption can result in
damage to the printer when it tries to position the assemblies. For
example, the printhead could be tilted forward and crash into the
raised cap/wipe/purge assembly.
Before turning on the printer, ensure the printhead is tilted
forward, centered in front of the drum and the cap/wipe/purge
assembly is in the retracted, home position. The tilt cam gear
should be disengaged from the gear drive train.
Electric clutches and solenoids are used by the printer to engage rollers as needed to move
paper through the printer as well as start some print processes.
Fig 1-11 Solenoids and clutches on the print engine
Cap/wipe/purge
clutch
Transfix
solenoid
Drum maintenance
cam clutch
Upper feed-
roller clutch
Pick clutch
Air valve
solenoid
0388-08