HP Color LaserJet Enterprise CP4020 - Page 56

Step 1: Pre-exposure
Light from the pre-exposure LED strikes the surface of the photosensitive drum to remove any residual
electrical charges from the drum surface.
Figure 1-13 Pre-exposure
Photosensitive drum
LED
Step 2: Primary charging
The primary-charging roller contacts the photosensitive drum and charges the drum with negative
potential.
Figure 1-14 Primary charging
Primary charging roller
Primary charging bias
Photosensitive drum
24 Chapter 1 Theory of operation ENWW