CHAPTER 4 IMAGE FORMATION SYSTEMCOPYRIGHT © 1999 CANON INC. CANON NP6320 REV.0 DEC. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)4-8IV. CONTROLLING THE DEVELOPING BIASA. OutlineThe circuit shown in Figure 4-402 controls the developing bias. Its main functions are asfollows:1. Switching AC component of the developing bias ON/OFF.2. Regulating voltage of the DC component of the developing bias.The copy density can be controlled by varying the voltage of the developing bias to suit thefollowing variables:1. Settings of the copy density lever and recalibration dial2. AE sensor outputThe photosensitive drum gradually deteriorates with use, causing the potential (VL) of lightareas of the drum to increase and making the copy density to be incorrect for a given setting of thecopy density lever. To compensate for this, a copy density knob, which can be turned to raise theDC bias by exactly the increace in VL, and thus to produce clear copies again.
