HP 8550mfp Service Manual - Page 455

Developer streak (See figure 225 on page 444 for an example of this print defect.) Developer streak is characterized by a line of dark or missing toner that stretches from the leading edge to the trailing edge. Replace the toner cartridge corresponding to the color of the developer streak (for example, if the streak is magenta, replace the magenta toner cartridge). Rain (See figure 226 on page 445 for an example of this print defect.) Rain is characterized by small, white, elongated spots in printed areas. Typically, rain begins toward the center of a printed page. Spots are elongated in the print direction. Rain is caused by particles of color toner scratching the imaging drum in some high-coverage, long-print-job conditions. Once the imaging drum has been damaged, it must be replaced. Eliminate rain by first checking manufacturer codes on toner cartridges (see "Toner cartridge manufacturing codes" on page 456) and replacing cartridges as needed. Then, check the imaging drum for pitting or contamination and replace the drum as needed. Toner bubbles (See figure 227 on page 446 for an example of this print defect.) Toner bubbles are characterized by large blotches of color toner on printed pages caused by color toner leaking from cartridges directly onto the transfer drum. Solve the problem of toner bubbles by checking the manufacturing codes on the toner cartridges (see "Toner cartridge manufacturing codes" on page 456) and replacing cartridges as needed. EN Image defects troubleshooting 453