I have just added a new drum in but it just prints grey. I've tried all settings and no joy. Same as the last machine. If I guess parts by the time a couple are purchased its the same price as a new printer!
You can try replacing the corresponding drum unit.
I am on my 2nd C600 and after 60,000 prints both machines seem to print fainter and fainter black in grey until they print no more. I use genuine drums but not genuine toner. I was told the drums will not last as long doing this but the cost made it worth it. However I have just installed a new black drum and it still won't print black. I have cleaned the lenses in the machine too. Anyone got any ideas or will I have to scrap another machine? Thnaks Peter