Canon CP660 Service Manual page 36

CHAPTER 1 GENERAL DESCRIPTION
Step 2 (primary charging)
In preparation for laser beam exposure, the surface of the photosensitive drum is
charged to a uniform negative potential. The machine's primary charging consists in
directly charging the photosensitive drum.
The primary charging roller is given a AC bias, in addition to the DC bias, to ensure
that the potential on the surface of the photosensitive drum will be uniform.
AC bias
DC bias
Step 3 (laser beam exposure)
When a laser beam is directed to the photosensitive drum, the charges in its light area
become neutralized, turning the area into a latent static image.
1-24
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Photosensitive drum
Figure 1-805
Laser beam
Dark area Light area
Figure 1-806
CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
Primary charging roller