HP 8000 s manual Sensor as described in Cleaning the Density Sensor

Problem	Cause and Solution
(Faded print, or random	The letterhead you are using is printed on rough paper.
faded areas, continued)	Try a smooth xerographic paper. If this solves the
	problem, make sure the letterhead vendor is using
	paper that meets the specifications for this printer. For
	media specifications, see “Supported Media Weights
	and Sizes for Input Trays” in chapter 3.
	You are operating the printer in excessively humid or
	dry conditions. Make sure the printer is operating within
	the environmental specifications listed appendix B.
	The media was creased or wrinkled when it was loaded
	in the input tray. Try media from a different source or
	from an unopened ream of media.
	The print on the entire page is light or faded. Remove
	the transfer assembly. Reinstall the transfer assembly.
	Be sure to align the arrows and then reseat the
	assembly.
	If you recently removed the imaging drum from the
	printer, it might have been damaged by light. Turn the
	printer off and on to reset the printer's density
	calibration. If the problem persists, replace the imaging
	drum or contact a local authorized HP dealer or service
	representative for service. For more information on
	replacing the imaging drum, see the installation guide
	included with the drum kit.
	If the print or the background is too dark, turn the
	printer off and on to allow the printer to adjust its color
	settings. If the problem persists, clean the density
	sensor as described in “Cleaning the Density Sensor”
	later in this chapter.

EN Print Quality Problems 191