Canon PC980 Service Manual - Page 111

CHAPTER 4 IMAGE FORMATION SYSTEM 2. Operations When measuring the density of an original, the scanner turns on the scanning lamp, and moves to a point 115 mm from the home position. At this time, the AE sensor reads the level of light reflected by the area shown in Figure 4-112, and sends the AE signal (AE) to the DC controller PCB. In response, the DC controller PCB sends the developing DCON signal (serial communication) to the composite power supply PCB according to the level of the AE signal. The microprocessor (Q900) on the composite power supply PCB controls the level of the DC bias applied to the developing cylinder based on the level of this signal. 68.8mm (approx.) 23.5mm (approx.) 5.8mm (approx.) 37.7mm (approx.) Middle of original : Area read by AE sensor Figure 4-114 Copy Start key ON STBY INTR AER SCFW SCRV SCFW SCRV LSTR STBY Main motor (M1) Scanner / lens drive motor (M2) Scanning lamp (LA1) AE signal (AE) Figure 4-115 COPYRIGHT © 1999 CANON INC. CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON) 4-17