HP 8550 Service Manual - Page 472

Halftone test print (TYPE=5) Use the halftone test print to check transfer faults, black lines, white lines, and uneven intervals. When using the halftone test print, set the density under TEST > PG > DENS-Y/M/C/K. l Transfer faults-If transfer faults occur, the intermediate transfer drum unit or the secondary transfer belt assembly of the printer unit is likely to be faulty. l Black lines-If black lines print on the copy, the photosensitive drum inside the drum cartridge of the printer unit is likely to have scratches, or the primary charging roller is likely to be soiled. l White lines-If white lines occur at the same position in all colors, the intermediate transfer drum or the secondary belt assembly of the printer unit is likely to be faulty. If they occur at different positions or in one color, the toner cartridge of the printer unit is likely to be faulty. l Uneven intervals-If uneven intervals occur, suspect the following: • If errors occur at 0.5 mm intervals, suspect the scanner. Scanner errors do not appear on test prints. • If errors occur at 66 mm intervals, suspect the developing cylinder. • If errors occur at about 52 mm intervals, suspect the registration roller. Figure 407. Halftone test print 470 Chapter 7 - Troubleshooting EN