thanks for your replies
i had changed the drums and th belt trensfer but the problem persiste.
Sometimes when a customer replaces a drum, a little piece of styrofoam sticks to the end of the drum causing the dev housing to bleed out. If that's the case you will need a tech to repair
Wow! Now I saw your pictures. Try to replace the Black drum cartridge and if the issue is not solved definetly you will need a tech because is an xerografic electrical discharge.
Print a Repeating Defects Page: press Machine Status button, go to Tools, touch Troubleshooting, touch Support pages, print the page and compare with yours print.
i have a xerox WC 7845 i have this problem in photo when i printing.