HP LaserJet M9040/M9050 Service Manual - Page 150

Table 5-9 High-voltage power supply circuits (continued) Bias generation circuit Purpose Developing bias The circuit controls the amount of toner transferred to latent images on the photosensitive drum. Pre-transfer upper guide bias The circuit prevents toner from adhering to the pre-transfer upper guide. Transfer bias The circuit applies specific bias levels to the transfer charging roller at specific times. ● Cleaning bias: Cleans the transfer charging roller by moving toner to the photosensitive drum. ● Between-page bias: Prevents residual toner from adhering to the transfer charging roller between pages of a print job. ● Print bias: Transfers toner to print media from the photosensitive drum. Separation static charge eliminating bias The circuit discharges media at delivery. Toner level detection The circuit monitors toner level via two antennae inside the print cartridge. Low-voltage power supply The low-voltage power supply consists of the fuser control circuit and the low-voltage power circuit. Figure 5-29 Low-voltage power supply The low-voltage power-supply circuit converts AC voltage DC voltage as follows: ● +24 Vdc for motors, solenoids, clutches, and for the high-voltage power supply ● +5 Vdc for the laser/scanner PCA, the beam detect PCA, and the formatter ● +3.3 Vdc for the formatter, the sensors, and the ICs on the DC controller PCA Fuser control circuit The fuser control circuit controls the temperature of the fuser roller and the pressure roller. It consists of the following components: 132 Chapter 5 Theory of operation ENWW