Tektronix PHASER 380, Service Manual

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5-24
Phaser 380 Color Printer
5
Theory of Operation
Drum preparation
To prepare the drum, oil is applied to the surface of the drum. First the drum is
rotated. Next, the wick and blade of the maintenance tray are raised into contact
with the drum. To accomplish this, the process motor rotates clockwise, driving
the process drive belt and the compound gear. Rotating clockwise, the
compound gear’s clutch drives a gear train that drives the maintenance tray’s
electric clutch which, in turn, engages the maintenance tray camshaft. The
electric clutch energizes, allowing it and the camshaft to rotate about one-half
revolution. The cams on the ends of the camshaft push against followers on
each side of the maintenance tray, forcing the wick and blade against the drum.
The de-energized clutch holds the camshaft in this position.
As the drum nears the end of its rotation, the maintenance cam electric clutch
energizes for a moment, allowing the camshaft to rotate further; this lowers the
wick but leaves the blade in contact with the drum to smooth out the last of the
oil on the drum.
The electric clutch energizes for a third time to allow the camshaft to rotate to its
home position, and lower the blade. The point at which the blade ends contact
with the drum it leaves a bead of oil, called an oil bar. The oil bar is left in a
40 mm (1.5 inch) swath of the drum; this swath is called the deadband. No ink
will be deposited on the deadband during the print cycle.
The paper stripper fingers, which lift the paper off of the drum during printing,
are lowered into contact with the drum in the deadband. The stripping
operation is timed so the fingertips avoid the oil bar which would stain the edge
of the print as the print is stripped off of the drum.