Canon PC980 Service Manual - Page 98

CHAPTER 4 IMAGE FORMATION SYSTEM C. Controlling the Primary Charging Roller Bias 1. Outline The circuit shown in Figure 4-103 is used to control the voltage applied to the primary charging roller, and has the following functions: • Turning on and off the DC/AC bias • Controlling the DC bias to a specific voltage • Controlling the AC bias to a specific voltage • Switching the level of the DC bias Both DC bias and AC bias are applied to the primary charging roller so as to ensure that the surface potential of the photosensitive drum will be uniform. The level of the DC bias is switched between when forming copy images and when not forming copy images. Reference: DC component: AC component: -400 V (non-image area)/-625 V (image area) 2000 Vpp to 3000 Vpp (885µA) 4-4 COPYRIGHT © 1999 CANON INC. CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)