Tektronix Phaser 840, Service Manual

Page: 188 / 207

Service Guide
177
Test Prints
This topic illustrates the service test prints produced by the printer. The test prints
push the printer to the extremes of its performance to reveal possible
shortcomings. Note that defects revealed by the prints may not show up at all in
the course of ordinary printing. In servicing the printer, you should minimize the
defects shown by the prints but not necessarily eliminate them.
1: X-axis motion.
These prints reveal problems with the
X-axis motion of the printhead. Look for:
1. A thin white line and black line are
normally present in the print
2. Uniform density. Look for uniform fill
from the left to the right edge of the
print. Lack of uniformity could be
caused by printhead-to-drum
misalignment. Lack of uniformity on the
edge of the print may be caused by
incorrect transfix roller pressure. A
defective printhead can also cause
uniformity problems, particularly if the
density difference is about 1/3 of an
A-size page wide. Narrower density
problems may be caused by a paper
preheater. Print Service Print 6.
3. Wrinkling. See Service Print 8.
Causes: Gaps could either be caused by
a defective X-axis drive or by something
else, such as a wiring harness interfering
with the horizontal movement of the
printhead. The ink loader, without the top
cover installed to secure it in place, may
rest too low and interfere with the
printhead’s motion. In this case the ink
loader should rest on extrusions on the
printer’s side frames. Also ensure that the
spring under the printhead is intact and
free of ink.
In the second print, the jagged black
bars in the four purple columns should
align horizontally. if they do not, adjust
the x-axis scale using the procedure, “X-
axis scale adjustment” on page 105.
1
3
4
2
0388-40