Chapter 66-66.5 Drum Unit6.5.1 Outline of the Drum Unit6.5.1.1 Outline 0020-4096Major components of the drum unit are as follows:F-6-7[1] Photosensitive drum[2] Cleaning blade[3] Primary charging roller6.5.2 Charging Mechanism6.5.2.1 Primary Charging Bias Control 0020-4097With the primary charging bias method, the drum is charged directly by the charging roller. In addition to a DC bias, an AC bias is applied to the primary chargingroller to stabilize charging. When the drum is charged, both AC and DC biases are applied. When the drum is discharged, only the AC bias is applied.The ASIC on the DC controller PCB outputs the primary bias drive signal (/PRACFOT), primary AC bias ON/OFF signal (/PRACON), primary DC bias drivesignal (/PRDCFOT), and primary DC bias output level signal (/PRDCPWM) to apply the voltage generated by superimposing the primary AC bias over the primaryDC bias to the primary charging roller.The primary AC bias is detected by the primary AC bias current detection circuit, and is fed back to the AC generator circuit via the comparison circuit.The primary DC bias is detected by the primary DC bias current detection circuit, and is fed back to the DC generator circuit via the comparison circuit. Thus, thismachine controls the primary DC bias voltage. The primary DC bias voltage changes with the developing DC bias voltage according to the image density informa-tion sent from the image processor PCB.F-6-8[3][1][2]JP3/JP4/PRACON/PRACFOT/PRDCPWM/PRDCFOTTo primarycharging rollerPrimary bias circuitASICCPUPrimary DC bias voltagedetection circuitDC generation circuitAC generation circuitComparisocircuitPrimary AC bias currentdetection circuitComparisoncircuitSuperimpositionHigh-voltage power supply PCBDC controller PCBJ214 J100/PRACMONI
