HP Designjet 250c Service Manual - Page 191

Banding Symptoms Random dark or light bands in area fills. (PrintĆQuality Plot ' page 8Ć56, 1. - Area Fills, and the offsetĆswath lines on the right of the plot.) (See also ' User's Guide, chapter 4.) Cartridge Fault D A nozzle is blocked or faulty and is not firing inkĆdrops. (PĆQ Plot ' 2. - Nozzle Checkout.) D The ink drops of one nozzle are of smaller volume than those of the other nozzles. D A nozzle's ink drop volume varies while plotting. D A nozzle's ink drops are misdirected: - Defect in manufacture of cartridge - Dirt or debris on the nozzle plate - Ink puddling on the nozzle plate D An electrical contact is misaligned or damaged on the cartridge, so that it doesn't make correct contact with the circuit on the carriage. (See ' page 8Ć39, w Carriage Test.) Plotter Fault D Incorrect swathĆadvance angle of the drive roller. This could be caused by a - Faulty roller (irregular roller radius / defective bearings) - MediaĆaxis inaccuracy (defective media motor or driver circuit / calibration lost) D An electrical contact is faulty in one of the plotter cartridge chutes, so that it doesn't make correct contact with the circuit on the cartridge. (See ' page 8Ć39, w Carriage Test.) D Nozzles touch the service station, thus causing puddling to occur on the printĆhead. D Some of the small slots on the encoder strip are damaged. Therefore the plotter cannot position the carriage correctly during cartridge servicing. D Cartridges are misaligned with respect to each other. D Calibration values lost or incorrect. Media Fault Some types of media have a coating that prevents them getting wet" from the ink drop. The ink doesn't spread out sufficiently around the point where the dot is placed. Banding may not occur on some poorĆquality media, where it is counteracted by another problem: large dot gain. This is where the ink spreads out excessively on the media around the desired dot position. To accurately test for banding, use HP polyester inkjet film. Solutions One or more of the following actions may be appropriate to solve a banding problem: D Prime/clean cartridges. D Reseat/replace cartridges. D Perform cartridge alignment. D Perform accuracy calibration D Reseat cartridge caps in service station. D Replace encoder strip. C4699Ć90000 Troubleshooting 8Ć57