6: 66% Gray, Dot Size Uniformity - Xerox Phaser 840 Service Manual

6: 66% Gray, dot size
uniformity
This print is made up of a 66% black fill. It
reveals variations in the ink-drop-spread caused
by thermal variations or transfix roller pressure
variations or drum oiling variations.
Look for: Large area of differences in the
density across the width of the page. (A slight
variation is normal.) Look for a lighter vertical
band, about 1/5 the width of the page, running
the length of the page. Also look for small, light
spots or irregular white lines, vertically aligned
with each other, in the print every 13.3 cm
(5.25 in.).
This pattern is sensitive to the density variations
in the paper it is printed on. Use a high-quality
grade of laser printer paper; otherwise, the print
will appear mottled.
Causes: Use the diagnostics to check the
printhead and drum for correct thermal
regulation. Also check the printhead-to-drum
gap (Phaser 840 only). Ensure the drum fan is
running properly. A vertical band, 1/5 of a page
wide, running the length of the page, is caused
by a stuck heating plate in the paper preheater.
Run the front panel cleaning procedure Clean
Ink Smears which raises the temperature of
the paper preheater and may free the stuck
heating plate. Additionally, you may manually
force a thick sheet of paper (65 to 80 lbs)
through the paper preheater to jar the plate free.
Light spots are caused by a defective transfix
roller with a weak, soft spot that is not pushing
the ink into the paper as the rest of the roller
does. In this case, replace the drum/transfix
unit. Replace the drum maintenance cartridge
roller; particularly if you observe variations in the
glossiness of the print.
Light band Light band
Uneven fill Uneven fill
Should see Should see
even fill even fill
left to right left to right
Test Prints 5 - 163
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