Xerox DocuColor 252 light band in cyan, ROS, developer and 1st BTR already replaced

[Detonation]

A customer has a DocuColor 252 which has a light band in cyan (see attached picture). It's in process direction, print in picture is A3.

I have already replaced the drum, developer housing, 1ST BTR, en ROS assy and cleaned the interior around the drum and under de ROS thoroughly. I don't think the ITB, belt cleaner or 2nd BTR can cause the problem as only cyan has it. I have replaced belt cleaner and 2nd BTR anyway as the were due. I'm kind of lost now, really have no idea what it could be.

[xcopytech]

Clean mirrors in ROS.

[Jake2o]

That does look like a ROS line dirt and debris on the mirrors / optics

[Detonation]

I've replaced the entire C,K ROS assembly...

[xcopytech]

It is ROS related 100%.
Did you replace CK ROS with new or used?

[Detonation]

A used one, but the banding remains in exactly the same location.

[xcopytech]

Remove ck ros. Then you will need to open ros and you will find toner debris on mirror.

[Jake2o]

It is a standard fault with the ROS units on these machines. And it will be 99% in the same place each and every time. It's centrifugal force that throws crap outwards and it clings to the optics inside the ROS assembly. As the spinner and polygon are in the same place and running at the same speed as every other ROS unit out there the line would be in exactly the same place each and every time.
Ozone and suction filter assembly need replacing on a regular basis and it helps cut down on this fault.

[Detonation]

Thanks Jake, it was indeed my main question how the line could be the exact same location. I'll clean out the ROS and let you know the result.

[Detonation]

Indeed, both ROS units had the band at the exact same location, d'oh! Cleaned it out with compressed air and machine is up and running again. Thanks for your help all!