Toner Pickup (Development); Figure 5-7 Toner Pickup - Tektronix PHASER 560 Service Manual

5
Theory of Operation

Toner pickup (development)

5-10 Phaser 560 Color Printer
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As the photoconductive belt continues to rotate, it passes by one of the four
toner cartridges. Each cartridge is selectively cam-driven forward to bring its
developer roller into direct contact with the belt when it is that cartridge's turn
to transfer its toner to the belt during the belt's four rotations past the cartridges.
The currently activated toner cartridge's developer roller is charged to a
potential between -120 to -220 volts. Toner is attracted to the exposed portions
of the belt in reverse proportion to the amount of negative charges left on the
belt. Since the charge on the exposed portions of the belt is about -20 volts, the
greatest amount of toner is transferred. The developer roller rotates at 1.6 (600
dpi printing) or 2.13 (1200 dpi printing) times the speed of the photoconductive
belt to ensure a constant supply of toner. As the belt advances, it passes the
pre-transfer lamp which, like the pre-exposure lamp, removes remaining
negative charges from the unexposed portions of the belt.
Developer roller
Photoconductive
belt

Figure 5-7 Toner pickup

Inside each toner cartridge is a toner supply roller which rotates in the opposite
direction from the developer roller. This supplies a layer of toner onto the
developer roller. The doctor blade smooths and evens out the toner on the
developer roller. Also inside the toner cartridge are gear-driven paddles the
churn the toner and keep it fluidized and moving towards the developer roller.
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-120 ~ -220v
Doctor blade
Paddles
Black
Supply
Cyan
roller
Magenta
Yellow
Toner cartridges
The pre-transfer
lamp removes
Pre-transfer
remaining negative
lamp
charges from the
unexposed portions
of the belt.
Cam driver
Toner is transferred
to the portion of the
belt exposed by the
laser beam.
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