Xerox 7800 Poor Print Quality, Grey Balance Issue

[CherylO-Xerox]

Hi JS_LD,

Thank you for using the Support Forum. Have you tried cleaning the the printhead lenses? Here are the instructions please make sure you have cleaned all four:

1. Open the printer Front Cover.
   
   
   
   
2. Rotate the orange lever to the left.
   
   
   
   
3. Pull the Drum Cartridge Cover down until it clicks into the open position.
   
   
   
   
4. Each of the four printheads has its own lens cleaner tool. Slowly pull the printhead lens cleaner out until the three dots are visible.
   
   
   
   NOTE: The printhead lens cleaner does not detach from the printer.
   
   
5. Slowly push the printhead lens cleaner tool back into the printhead until it stops.
   
   
   
   
6. Repeat steps 4 and 5 for each printhead.
7. Close the Drum Cartridge Cover.
   
   
   
   
8. Rotate the orange lever to the right, to return the lever to the locked position.
   
   
   
   
9. Close the printer Front Cover.

If the problem continues please consider contacting your support centre for further assistance.

[JS_LD]

We are experiencing print quality deterioration with our Xerox 7800. The prints are full of horizontal and vertical lines, they look almost as if there is a line screen on the image. We have ran paper calibrations as well as color calibrations. While calibrating the grey balance, there isn't an option that is actually a neutral grey. This is evident in all three shades, but especially in the dark calibration. This seems like some sort of ink contamination issue. We only use OEM cartridges. Further, the color the printer yeilds is very innacurate / muddy. This occurs with both the printer managing colors and with photoshop managing colors using profiles we created and sucessfully used in the past. 

Any ideas are appreciated. 

Using Mac OSX 10.12.5; Photoshop CC 2015