COPYRIGHT © 1999 CANON INC. CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)3. Black Developing Bias Generation CircuitThis circuit is controlled by three signals (Figure 4-606) from the DC controller PCB,and generates the black developing DC bias and black developing AC bias for applica-tion to the black developing cylinder.The black developing AC bias drive signal is used to turn on and off the AC biasapplied to the black developing cylinder, while the black developing DC bias drive signalis used to turn on and off the DC bias applied to the black developing cylinder.The black developing bias level control signal, on the other hand, is used to switch thelevels of the black developing DC bias. (See Note.)The black developing bias generation circuit contains the black toner level detectioncircuit, which compares the output of the black developing AC bias and the output of theantenna mounted inside the cartridge for output to the DC controller PCB as the blacktoner level detection signal.The DC controller PCB checks the voltage of the black toner level detection signal tofind out the level of toner when the black developing AC bias is applied to the black devel-oping cylinder.Figure 4-606Note:The black developing DC bias level for image areas is varied in response to the den-sity command from the printer board*1 or based on the result of image density cor-rection control (p. 4-21).*1 Rear controller PCB (when making prints with the reader unit installed).CHAPTER 4 IMAGE FORMATION SYSTEM4-29DC controllerPCBBlackdeveloping biasgenerationcircuitBlack developing DC bias drive signalBlack developing AC bias drive signalBlack developing bias level control signalBlack developingcylinderBlack tonerleveldetectioncircuitBlack toner level detection signalAC+DC (negative)Black tonerleveldetectingantennaDownload free service manual at http://printer1.blogspot.com
