Canon PC940 Service Manual - Page 105

CHAPTER 4 IMAGE FORMATION SYSTEM E. Controlling the Developing/Separation Static Eliminator Bias 1. Outline The circuit shown in Figure 4-107 is used to control the voltage applied to the developing assembly and the separation static eliminator, and has the following functions: • Turning on and off the developing DC bias • Turning on and off the AC bias (turning on and off the static eliminator bias) • Controlling the voltage level of the developing DC bias Both AC bias and DC bias are applied to the developing cylinder while copies are being made. When the photosensitive drum rotates and yet developing is not under way, about -500 VDC is applied to the developing cylinder regardless of the position of the density adjusting lever, thereby preventing adhesion of excess toner on the photosensitive drum. Reference : Developing DC bias : -80 ~ -550V Developing AC bias : 1200Vpp ± 10% COPYRIGHT © 1999 CANON INC. CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON) 4-11