We have a Phaser 6300 at work and it's been more than a week that the printer is not working properly.
As you can see on the picture the problem is concerning the black ink: it works on the borders but not in the middle. But the blue and all the other colors are working well. We change the black ink tank and the imaging unit and still nothing. We tried to shake the ink tank but it just spreads out everywhere. What I noticed is that the ink is getting out only from one of the tank's edge not through the "rectangle".