HP d640 HP D640 High-Volume Printer - User Manual (Printer and Accessories), C - Page 180

Advanced Topics Maintaining Print Quality Lines If sharp or smeared black streaks appear on the page (in the direction the paper passes through the printer): • Toner may be on the transfer charger or pre-charger corona wires. Clean the printer's transfer assembly unit and precharger. (See "Transfer Assembly Guide" on page 5-9.) • Replace the drum unit with a new one. (See "Drum Kit Replacing Drum and Transfer Assembly" on page 4-18.) • If you still have this print quality problem, contact your authorized HP service representative. Toner Smear If toner smears appear on the leading edge (as is passes through the printer) of the paper: • Toner may be loose inside the printer's paper path. Clean the printer by following the instructions in "Periodic Cleaning (When Replacing Drum)" on page 5-5. • Replace the drum unit with a new one. (See "Drum Kit Replacing Drum and Transfer Assembly" on page 4-18.) • If you still have this print quality problem, contact your authorized HP service representative. Background Gray Toner Shading If the amount of background toner shading becomes unacceptable: • The print density setting may be too high. Adjust the print density (See "Density" on page 2-25.) • Toner may be on the transfer charger or pre-charger corona wires. Clean the printer's transfer assembly unit and precharger. (See "Transfer Assembly - Transfer LED Areas" on page 5-6.) • Change the paper to a lighter basis weight. • Check the printer's environment; very humid conditions can increase the amount of background shading. • Replace old developer with fresh developer. (See "Replacing Developer" on page 4-9.) • Replace the drum unit with a new one. (See "Drum Kit - Replacing Drum and Transfer Assembly" on page 4-18.) • If you still have this print quality problem, contact your autho- rized HP service representative. Advanced Topics 6-5