Xerox Phaser 3450 Service Manual page 149

CIRCUIT DESCRIPTION
11.3.1 Introduction
HVPC applies DC+24V/ DC+5V, which is used to form image in the electric photo development process of OAequipments.
It yields MHV, SUPPLY, DEV, and THV.
Each high pressure output indicate the voltage required for the electric photo process.
11.3.2 Electric Photo Process
Electric photo process is widely used to the image creation features of copying machines, laser beam printers and
facsimiles. It's process involves transferring, exposing, developing, transferring and settling in respective order.
HEATER ROLLER
PRESSURE ROLLER
First, form uniform electric charge of -800V on the surface of OPC with -1,380V(adjusted) through transfer roller. The
electrically charged OPC drum surface react to the image data from LSU, which received print order based on the rotation
and becomes exposed. At this time, the areas that are not exposed will maintain the previous electric potential of -800V.
The exposed image areas by LSU will contain approximately -150V and form charge ripple. Such drum surface of reduced
exposure, which formed charge ripple, reaches the develop roller according to the drum rotation and goes through the
development process. The charge ripple formed on the OPC drum surface is developed by the toner on the develop roller
and transforms into image. This step converts the image formed on the OPC drum surface by LSU to the image formed
by toner.
The supply roller that received -650V(adjusted) from HVPS and the DEVE roller that received -470V(adjusted) will rotate
in the same direction. The toner supplied to the OPC drum becomes negatively(-) charged due to the static formed between
the two rollers. The toner supplied to the develop roller is transferred(BIAS) to the development section. The negatively
charged toner is attached to the develop roller, then transferred to the exposed high electric potential surface(-150V) rather
than low electric potential surface(-800V). The image is formed since the toner is not spread on the low electric potential
surface. The transfer process takes place when the OPC drum continuously rotates and reaches the transfer section. The
(-) toner on the OPC drum surface is transferred to the paper surface by transfer roller. The (-) toner on the OPC drum
surface receives hundreds up to thousands of (+) volts from HVPS and transferred to the paper surface since the (+)
voltage is larger than the (-) toner on the OPC. The toner with weak static energy settles on the paper by pressure and
heat from the pressure roller and heat roller. The printing process is completed when the pressure from the pressure roller
and the heat from the heat roller forces the melted toner to settle the image on the paper surface and the paper exits the
printer.
Service Manual
11-18
LSU
MHV
TRANSFER
ROLLER
SUPPLY
DEV
SUPPLY ROLLER
DEVELOP ROLLER
Paper Transfer Direction
THV
TRANSFER
ROLLER