HP 8550 Service Manual - Page 480

Contact (for 8 color developing bias) High-voltage 9 PCB 1 (inadequate color developing bias output) 10 Intermediate 11 transfer drum High-voltage 12 PCB 1 (inadequate primary transfer bias output) Secondary 13 transfer belt assembly High-voltage 14 PCB 2 Is the contact for the color YES developing bias for the printer unit soiled? Open the front cover while NO toner is being developed on the photosensitive YES drum (about 20 seconds after the start of test printing), and take out the black toner cartridge. Then, take out the drum cartridge, and check the toner image on the surface of the photosensitive drum. Is the color toner image fully developed on the surface of the photosensitive drum? Open the right cover of the NO printer unit, and fit the door YES switch actuator. Make a copy, and check the toner image on the surface of the intermediate transfer drum. Is the toner image fully developed on the surface of the intermediate transfer drum? Are the contacts soiled on YES either of the following? l intermediate transfer drum unit l primary transfer bias Replace the high voltage PCB 1. Is the problem corrected? NO YES Clean the contact. If it is damaged, replace the problem part. Also, check for a displaced contact. Replace the high-voltage PCB 1. Replace the dc controller PCB. Go to step 11. Go to step 13. Clean the contact. If it is defective or damaged, replace the problem part. Also, check for a displaced contact. Go to step 13. End. Are the contacts soiled on YES either of the following? l secondary transfer belt assembly l secondary transfer bias Replace the high-voltage PCB 2. Is the problem corrected? NO YES Clean the contact. If it is defective or damaged, replace the problem part. Also, check for a displaced contact. Replace the dc controller PCB. End. 478 Chapter 7 - Troubleshooting EN