Ricoh AC205 Service Manual - Page 166

SMPS AND HVPS 6.4.1 HVPS The HVPS supplies the following voltages to the machine: Transfer High Voltage (THV+): This voltage transfers toner from the OPC drum to the paper. • Output voltage: +1300V DC ±20V • Failure Symptom: Low-density printing occurs due to toner on the OPC drum that was not transferred to the paper due to THV (+) not present. If this condition persists, waste toner over-flow can occur. Ghost images may appear which repeat at 76mm intervals. Charge Voltage (MHV) This voltage charges the surface of the OPC from -900V to -1000V. • Output voltage: -1550V DC ± 50V • Failure Symptom: Toner particles are transferred to the whole OPC drum surface if MHV is not present due to the OPC drum surface having no charge. In this condition, a black page is printed out. Cleaning Voltage (THV-): This voltage removes toner contamination from the rear-side of the paper by sending negative polarity to the transfer roller. This forces toner to transfer back to the to OPC drum. • Output Voltage: -1200V, +300V/-150V • Failure Symptom: Smudges and toner contamination appear on the reverse side of the printed page. Developing Voltage (DEV): This voltage develops the toner on the section of the OPC drum surface exposed by the LSU. At printing, the exposed voltage on the OPC is -180V. Unexposed voltage is -900 to -1000V. The exposing voltage on the DEV is -430V. Therefore, toner with negative polarity is developed onto an exposed section of the OPC. • Output voltage -430V DC ± 20V • Failure Symptom: • Print density becomes extremely light if DEV is GND. • Print density becomes extremely dark when DEV is "floating", due to poor connection between the frame and cartridge contacts, etc. B273 6-12 SM