Electrostatic Charging; Figure 5-4 Electrostatic Charging Of The Photoconductive Belt - Tektronix Phaser 550 Service Manual

Electrostatic charging

The electrostatic potential of the belt is not uniform following pre-exposure. As
the belt rotates, it passes a scorotron charger which bombards the belt with
negative charges. The scorotron charger behaves somewhat like a vacuum tube.
The grid of the charger, held at a potential of between -500 volts (for 1200dpi
printing) to -550 volts (for 600 dpi printing) and coupled with the varying
voltage potential on any discrete point on the belt's surface, determine how
many electrons can flow from the corona wire onto that point of the belt's
surface. The corona wire is charged to -6 kvolts with a constant current of
400 µ A. The varying electron output from the scorotron, directly based on the
varying charge of the belt surface, results in a uniform negative potential on the
belt surface of -500 volts or -550 volts, depending on the selected dot-per-inch
printing.
Scorotron
charger
-6kv
The scorotron
charger lays down
a uniform negative
charge on the belt
surface.

Figure 5-4 Electrostatic charging of the photoconductive belt

Grid -500 -550v
9322-82
Service Manual
5
Theory of Operation
5-7