Tektronix PHASER 840 Quick Reference Manual page 146

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 PC diagnostics to check
the printhead and drum for good thermal
regulation. Also check the
printhead-to-drum gap. Ensure the drum
fan is running properly. A vertical band,
1/5 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#)
though 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.
136 Phaser 840 Color Printer
Light band Light band
Uneven fill Uneven fill
Should see Should see
even fill even fill
left to right left to right
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