Tektronix Phaser 340 Service Manual page 283

Printers serial numbered BC xxxxx and up.
Service Test Print 6 - Black dither pattern. 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 tray; particularly if
you observe variations in the glossiness of the print.
Test Patterns
Light band
Uneven fill Uneven fill
Should see Should see
even fill even fill
left to right left to right
Service Manual
B
9100-88
B-9