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01-13-2011, 02:17 AM
I have a C6501 and recently we've had a color issue that the tech can't seem to resolve. The color is not consistent from the left to right side of the sheet (when holding an 13 x 19 Sheet Vertically) There is a strong Magenta cast that is affecting the color on the left side of the sheet. This is most apparent in halftones. We've tried the density adjustment in the machine but its not working. The tech has done a full PM - replaced Drums, Corona, Dev. Housing, Developer, etc.

The best way to describe it is like there is a gradation of magenta from the left to right of the sheet - worse on the left side (ie. problem is on the left side and gradually gets
better as it moves to the right). I've attached a file that emulates the issue...
Hope someone can help...


01-13-2011, 03:43 AM
I think the problem is related to the lack of alignment between the drum and the corona magenta (grid). The drums have at the ends of the supports that regulate the position of the coronas. I adjust the height of the rear. On the italian site is a technical news that talks about this problem. Hope this helps.

Mr Spock
01-13-2011, 04:47 AM
Check the coronas for the wire being out of place. I have seen this on several of these units.

01-13-2011, 06:54 AM
I'm with Mr Spock on the corona wire thing.

Do a half tone of each colour at about 150-180 to verify which colours are affected. Yellow is hard to tell, so blend that colour with one of the other halftones that you know is even to see if Yellow is also uneven. Swap the charge unit of the uneven colour with another charge unit that has even colour and see if the problem moves. If so, the charge wire inside is not sitting correctly.

To check the wires, simply pull out the charge unit and lift up to a decent light source and peer through from the bottom of the unit to see the wire silhouette at each end. To know if they are centered, the plastic housing where the wire enters into, the wire should be in the center of this as you look. If not, using a q-tip, gently push on the wire from underneath and it should pop into the correct position. I stress gently, the wire is quite fragile and these units are unserviceable to replacing the wire, the whole unit needs replacing.

If the uneven density is not due to the charge unit, see attached file for further instructions.

Also, check to ensure the registration sensors are clean, and of course, when all is said and done, perform another drum potential adjust along with auto gamma adjust to ensure proper densities are being measured.

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