Lexmark X642e Service Manual page 201

Print quality—banding
Service tip: Banding is difficult to detect, except on a page with a uniform gray or a large amount of graphics
printed on the page. Banding is primarily due to a variation in the speed of the paper as it feeds through the
printer, especially in the development and transfer process. Inspect the alignment assembly, main drive
assembly, and all other paper feed components for signs of wear, dirt, binds, or damage, especially the drive
gears. Banding appears as light or dark horizontal lines on a uniformly gray page.
Banding can also be caused by a defective charge roll brush contact or HVPS. Check the charge roll contact for
damage and for proper connection to the HVPS and print cartridge.
Print quality—black bands on outer edges of the page
This print quality problem appears as vertical black bands on one or both sides of the copy and can be wide,
narrow, light, or dark.
FRU
1 Charge roll counterbalance
springs
2 Charge roll assembly
Charge roll link arm
3 HVPS
Print quality—residual image
Service tip: Install a new print cartridge if available before doing this service check. Residual image can be
caused by the photoconductor, cleaning blade, and other parts inside the print cartridge.
FRU
1 Hot roll fuser assembly
Action
If the problem is just on one side of the page, check the charge roll
counterbalance spring on that side. You can check to see if enough
force is being applied to the charge roll by applying slight downward
pressure with your finger to the charge roll link arm that the spring is
attached to while you run a print test sample. See if the problem
changes or goes away. If this fixes or changes the problem, then
check the springs and charge roll link arm assemblies for binds or
defective parts. Replace as necessary.
Check the charge roll for toner buildup or other contamination on the
outer edges that correspond to the bands on the page. Check the
charge links and arms for proper operation, binds or incorrectly
mounted counterbalance springs. Repair or replace as necessary.
Check the following voltages at J15-8 on the system board:
• Printer Idle
J15-8 measures 0 V dc
• Printer Printing Test Page
J15-8 voltage changes from 0 V dc to +4 V dc
If the voltage does not vary, check the continuity of line J15-8 in the
front cable harness. If there is no continuity, replace the cable
harness. If there is continuity, replace the HVPS. If this does not
correct the problem, replace the system board.
Turn the printer off, and check the resistance between J15-7 and
printer ground. The resistance measures approximately 0 ohms. If
incorrect, make sure the system board is mounted correctly and
securely grounded. If correct, replace the system board.
Action
Check the fuser assembly for toner contamination. The hot roll
especially might cause toner to be retained and deposited on the
page.
7002-xxx
2-163
Diagnostic information