Canon NP6218, FY8-13EX-000 Turning On and Off the AC Component of the Development Bias

CHAPTER 4 IMAGE FORMATION SYSTEM

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 VL, thereby freeing the copies of fogging.

(to lighter) (to darker)

VR302

Developing bias (DC component)

		Darker
-500		Medium
		Lighter
-400
-100
(darker)	5	(lighter)

Copy density

Figure 4-205

4-26 COPYRIGHT © 1997 CANON INC. CANON NP6218 REV. 0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)