Brother International HL-1660E Service Manual - Page 23

Step 1 Primary charge Primary charging roller AC bias DC bias Photosensitive drum Figure 2.9 As preparation for latent image formation, a uniform negative potential is applied to the photosensitive drum surface. The printer uses the charging method that directly charges the drum for the primary charge. The primary charging roller consists of conductive rubber. In addition to DC bias, AC bias is applied to the primary charging roller to keep the potential on the drum surface uniform. This DC bias is changed with the developing DC bias. This charging method has advantages such as lower applied voltage, less ozone generation, etc., compared with the corona charge system. Step 2 Scanning exposure Laser beam ___ +++ Unexposed area Exposed area Figure 2.10 When the laser beam scans the drum surface, it causes the charge to be neutralized in the areas struck by the beam. Areas on the drum with no charge form the electrostatic latent image. II - 7