Canon NP6330 Service Manual page 109

CHAPTER 4 IMAGE FORMATION SYSTEM
2. Turning On and Off DC Component of the Developing Bias and Controlling the
Voltage Level
The developing DC bias ON command (DPON*) generated by the DC controller is
used to turn on and off the DC component of the developing bias. The level of the voltage
is controlled by the DC bias control command (DCBC).
• When the DC component of the developing bias is on,
DPON*=0
→The remote circuit turns on.
→The amplifier circuit turns on.
→The DC drive circuit turns on.
• When the developing bias DC component is off,
DPON*=1
→The remote circuit turns off.
→The amplifier circuit turns off.
→The DC drive circuit turns off.
As shown in Figure 4-109, the voltage level of the DC component of the developing
bias is controlled by varying the voltage of the DCBC command (analog) generated by
the DC controller to suit the setting (output from the AE sensor) of the Copy Density key.
The level of the DC voltage generated by the high-voltage power supply varies according
to the level of the DCBC command.
With the exception of during copying operation (SCFW), the machine applies a DC
bias of about -320 V, thereby preventing undesirable adhesion of toner in areas between
sheets of copy paper and fogging in copy images.
Developing DC bias (V)
4-12
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→The DC high-voltage transformer turns on. (developing DC bias
output)
→The DC high-voltage transformer turns off.
-500
-100
F1
Figure 4-109
F9
Copy density
CANON NP6330 REV.0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)