Lexmark XC4150, Service Manual

Page: 538 / 575

The transfer belt carries the four-colored image towards the transfer rolls. Paper is picked up from the tray and
carried to the transfer roll where the image is transferred from the transfer belt to the paper. The timing of the
paper pick is determined by the speed of the transfer belt.
The paper is carried to the fuser rollers where heat and pressure are applied to the page to permanently bond
the toner to the page. The fuser rollers push the paper into the output bin. The transfer unit is cleaned and the
process begins again for the next page.
Step 1: Charge
During the charge step, voltage is sent from the HVPS to the charge roller beside each of the four
photoconductors. In this printer, the charge roll is part of the photoconductor unit in the print cartridges.
The charge roller puts a uniform negative charge over the entire surface of the photoconductor to prepare it
for the laser beam.
Service tips
•
If the surface of the charge roller is damaged (such as a nick or pit), it will cause the charge on the
photoconductor to be uneven. This causes a repeating mark on the printed page. Check the service manual
for the repeating marks table.
•
If the charge roller is severely damaged, the surface of the photoconductor will not be not be properly
charged and heavy amounts of toner will be deposited on the photoconductor. This causes the printed page
to be saturated with 100% of each color. The imaging kit will need to be replaced sooner.
Step 2: Expose
During the expose step, the laser fires a focused beam of light at the surface of each photoconductor and writes
an invisible image, called a latent image or electrostatic image, for each color.
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Appendix C: Theory of operation
538