Lexmark T620 Service Manual - Page 145

4069-5XX/7XX 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 any signs of 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 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 a 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. Diagnostic Information 2-117