2: Weak/Missing Jet; 3: Color Bands, Rgbk Dither - Xerox Phaser 840 Service Manual

2: Weak/missing jet

This print shows which jets are not outputting
enough, if any, ink compared to its neighboring
jets. Note that the yellow jets' bands have a
small amount of cyan ink added to them, which
tints them green, to make them more visible.
Look for: No interlacing is used in this print;
expect light/dark variation between jets. Look for
much lighter colored vertical bands in the
horizontal bars. Weak jets in the yellow band are
distinguished by a cyan tint.
Causes: A jet may be partially clogged; perform
printhead clean/purge cycles on the printhead to
remove contaminants from the poor-performing
jet. Test the vacuum system of the
cap/wipe/purge system. Turn the printer off for 4
to 6 hours (or overnight, if practical). Then
perform a clean/purge cycle again. As a last
resort, replace the printhead.
3: Color Bands, RGBK
Dither
The large, secondary colored areas in this print
reveal banding and weak jets.
Look for: Vertical "bars" or bands of much
lighter color or a different hue running in-line in
one or more of the solid fills.
Causes: Banding is caused by color-to-color
misregistration. Ensure the printhead-to-drum
spacing is correct. Then use the PC diagnostics
to ensure that the printhead and drum thermals
are correct. A weak jet can also cause banding;
refer to the Weak/missing Jets test print. Make
sure that the drum temperature sensor is
correctly mounted and in proper, even contact
with the drum. If necessary, remove the sensor
and check it for an accumulation of debris at its
contact point. As a last resort, replace the
printhead.
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Test Prints
Weak jet
9923-114
Banding
9923-115
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