Xerox Phaser 6250DT, Service Manual, Page: 42 / 467

Theory of Operation 2-3
surface is attracted by the high positive potential and transfers to IDT1. During
this transfer, the remaining negative charge on the drum is neutralized by the high
positive charge on IDT1.
5. Secondary Transfer (IDT1 --> IDT2):
The toner images formed on both
IDT1 surfaces are then transferred onto the surface of IDT 2 to create a complete,
4-color toner image. IDT2 is also conductive and receives a positive voltage from
the HVPS. The received voltage puts IDT2 at a higher potential than IDT1 thus
attracting the toner image and facilitating the transfer.
6. Cleaning: The IDT1 cleaner consists of a conductive roller brush rotating in
contact with IDT1 after the point where the toner is transferred to IDT2. The
cleaner receives a high positive voltage from the HVPS allowing it to electrically
attract any toner particles remaining on IDT1. Toner remaining on both IDT1’s
after the image transfer to IDT2 is temporarily stored in the IDT1 cleaners.
7. Tertiary Transfer:
The finished toner image on IDT2 is transferred onto the
print media using the voltage supplied by the transfer roller. The conductive
transfer roller receives a high positive voltage from the HVPS that puts it at a
higher potential than IDT2. Since the transfer roller is located behind the print
media, the 4-color toner image is attracted to the high potential and deposits on
the surface of the print media.
8. Cleaning:
The IDT2 cleaner consists of a conductive roller brush rotating in
contact with IDT2 after the point where the toner is transferred to the print media.
The cleaner receives a high positive voltage from the HVPS allowing it to
electrically attract any toner particles remaining on IDT2. Toner remaining on
IDT 2 after the image transfer to the print media is temporarily stored in the IDT2
cleaner.
9.
S
tatic Elimination: The positive charge on the print media can cause image
quality problems by scattering toner. To prevent this, negative DC voltage from
the HVPS is applied to the back side of the print media by the Detack Saw,
located on the Transfer Roller Assembly. This negative charge neutralizes and
eliminates the charge on the print media resulting from the tertiary transfer.
10. Fixing:
The finished toner image is unstable and easily smeared. To fix the
image, the print media goes through the Fuser Assembly where it passes between
a pressure belt and the heat roller. The toner is fused onto the print media by the
combination of heat and pressure.
11. Cleaning:
During the general cleaning process, the voltage applied to the IDT
rollers and drums go through a cycle of changes to move the negative and
positive charged toner particles from the cleaners and IDTs and then the transfer
roller. The toner stored in the IDT1 cleaner, the IDT 2 cleaner and on the transfer
roller is removed and deposited into the transfer roller waste recovery bin. Toner
from the charge roller and refresher is also removed and deposited into the
transfer roller waste recovery bin. In each case the voltage at the point of
attraction is set high and the voltage at the point of disposal is set to 0V with the
result that the toner is moved to the high potential until at last it is deposited on
the transfer roller. Toner is removed from the transfer roller by the attached
cleaning blade and deposited in the attached recovery bin.