Banding problem on a QSS 3501 plus

[lea.mado]

Hello, 

We happen to have lines on our images... Just like those in the photo (really subtle but once you see it, it's the only thing you see !!). Does anyone know what might cause the lines and how to solve this problem ? 
We think we might need to perform an Exposure Advance Adjustment 1, yet nothing seems to change.

Thank you for your answers !! 

[alexvigor]

I'm not sure about qss35 series, but i've seen such banding on qss32/37 machines. The cause was dirty shafts under exposure advance belt, although in that case the banding should be even throug all of the print. I can't tell if it is so on your picture. In any case the problem is definately in exposure advance unit. Might be the bearings.

Edited January 29 by alexvigor

[Dave S]

Probably bad bearings on the exposure advance unit.

Is it along the whole length of the print, is it a repeating patten?

A plain grey print would be much better to show the banding more clearly.

[lea.mado]

Hello, 

Thank you for taking the time to answer. 
Here is a photo of a confirmation print we did yesterday. I am sorry for the bad ligthing but if you zoom in especially in the light grey part, you will see the pattern. 

The lines are all along the length of the prints but they are more visible at 20mm, 35mm and 75mm (on a 9cmx13cm on a 127 mat paper).

It might be dust like Alex said, or we might need to replace something.

[Dave S]

It's very had to see clearly, it would be much better if you scanned the print with a flatbed scanner.

It looks like the pattern repeats at regular intervals, that would likely indicate some dirt in one particular place, probably on a drive belt or pulley wheel.

If you rotate the rollers by hand you may feel a tiny bump when it gets to the problem area.