HP LaserJet 9040/9050 Service Manual - Page 95

Each of the bias generation circuits has a specific purpose: z Primary charging bias generation. Applies bias to the primary charging roller to spread a uniform, negative charge on the photosensitive drum. z Developing bias generation. Controls the amount of toner transferred onto latent images formed on the photosensitive drum. z Pre-transfer upper guide bias generation. Prevents toner on the photosensitive drum from adhering to the pre-transfer upper guide. z Transfer bias generation. Each of the three types of transfer bias (cleaning bias, between-page bias, and print bias) is applied to the transfer charging roller at specified intervals. z Cleaning bias. Cleans the transfer charging roller by moving toner to the photosensitive drum. z Between-page bias. Prevents residual toner on the photosensitive drum from adhering to the transfer charging roller between pages of a multi-page print job. z Print bias. Transfers toner from the photosensitive drum to the print media. z Separation static charge eliminating bias. Stabilizes media delivery. z Pressure roller bias generation. Prevents toner from adhering to the fuser roller. z Toner level detection. Monitors toner level through two antennae (plate antenna and flat antenna) in the print cartridge. Engine control system 79