HP LaserJet Enterprise 600 Service Manual - Page 47

Block 1: Latent image formation During the two steps that comprise this block, an invisible latent image is formed on the photosensitive drum. Step 1: Primary charging To prepare for latent image formation, the surface of the photosensitive drum is charged with a uniform negative potential. The product charges the photosensitive drum surface directly from the primary charging roller. The DC bias and AC bias are applied to the primary charging roller to maintain a constant charge on the drum surface. Figure 1-16 Primary charging Primary charging roller Photosensitive drum AC bias DC bias Step 2: Laser-beam exposure The laser beam scans the photosensitive drum to neutralize the negative charge on portions of the drum surface. An electrostatic latent image forms where the negative charge was neutralized. Figure 1-17 Laser-beam exposure Laser beam Unexposed area Exposed area ENWW Image-formation system 23