Xerox Phaser 6200B, Service Manual

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306 Phaser 6200 Color Laser Printer - Service Manual
Process Control
For stable printing, the parameters related to the image forming must be monitored
and adjusted by the printer. Parameter correction and control over the entire printing
process is called “process control”. There are two main controls:
■
Bias Control
■
Toner Density Control
To supplement these two controls, the following are provided:
■
High-Area Coverage Mode
■
Admix Mode
■
CTD Sensor (ADC - Automatic Density Control) LED light density setting.
Bias Control
To attain stable image density, the drum charging voltage and the developing DC
voltage are continuously adjusted according to the developing capability of each
color. The adjusted drum charging voltage and the developing DC voltage are fed
back to keep the image density constant.
The bias control is made immediately before the start of printing, if any of the
following conditions is satisfied:
■
First print produced after the power on.
■
Accumulative print count exceeds 16 after power on.
■
When a cleaning cycle is executed during continuous printing.
The outline of toner density control is as follows.
1.
The Temperature/Humidity Sensor detects the temperature and humidity, and sets
the target values of the drum charging voltage and developing DC voltage.
2.
The patches of respective colors (yellow, magenta, cyan, and black) for the bias
control are generated and transferred to the Transfer Roller.
3. The CTD (ADC) Sensor detects the density of the
patches and area on the Transfer Roller where no toner
is present.
4. The density measured in Step 3 is compared with the
target value set in Step 1 to adjust the drum charging
voltage and the developing DC voltage for each color
according to the difference in value.
Y
M
C
K
About 11mm
About 57mm
engine principle0046FA
About 12mm
About 3mm
S6200-053