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3. Turning On and Off the AC Component of the Development Bias
The microprocessor (Q512) on the composite power supply PCB generates the
ACBIAS signal (pulse signal) under the control of the microprocessor master (Q301) on
the DC controller PCB. In response to the signal, the development bias AC component
generating transformer (T301) turns on to add the AC component of the development
bias to the DC component for application.
• application frequency 2400 Hz (approx.)
• application voltage 1300 Vp-p (approx.)
4. Controlling the Voltage Level of the DC Component of the Development Bias
The copier modifies the voltage level of the DC component of the development bias
based on the following factors:
• setting of the Copy Density key
• output of the AE sensor
• position of the Copy Density Correction knob (VR302)
The copier controls so that the voltage of the DC component of the development bias
varies between –80 and –560 V (in actual terms) by varying the output of the BPWM
signal.
To ompensate increases in the
light
potential (VL) caused by deterioration of the
photosensitive drum, the copier is equipped with a copy density correction volume. You
may operate the volume (VR302) on the DC controller PCB to adjust the potential of the
DC bias for any increase in V
L, thereby freeing the copies of fogging.
Figure 4-205
COPYRIGHT
©
1997 CANON INC. CANON NP6218 REV. 0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 4 IMAGE FORMATION SYSTEM
4-26
(to lighter) (to darker)
VR302
Developing bias
(DC component)
-500
-400
-100
Darker
Medium
Lighter
(darker) 5
Copy density
(lighter)