COPYRIGHT © 1999 CANON INC. CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)E. Detecting the Level of Color TonerThe level of color toner is detected by the color toner level sensor (PS621), which con-sists of a light-emitting section and a light-receiving section.The light from the light-emitting section found on the outside of the toner cartridgesmoves through the light guide to reach the detecting window inside the cartridge.The stirring plate inside the cartridge moves away toner from around the detectingwindow so that the light moves through the cartridge and reaches the light-reflecting sec-tion of the sensor through the light guide. Then, as toner once again starts to cover thedetecting window, the DC controller PCB finds out the time that passes before the lightis blocked.When the period during which light moves through the cartridge is longer than a spe-cific value, the DC controller PCB identifies the condition as absence of color toner, andcommunicates the fact to the printer board*1.The machine checks the level of toner in reference to the timing at which the stirringplate is rotating when power is turned on or when making prints.*1 Reader controller PCB (when making prints with the reader unit installed).Figure 4-304CHAPTER 4 IMAGE FORMATION SYSTEM4-16DC controller PCBLight-emittingsectionColor tonerlevel sensor(PS621)CTNSNSCTNLEDLight-receivingsectionColor tonercartridgeLight guideDownload free service manual at http://printer1.blogspot.com
