My MX870 has suddenly developed a strange misalignment problem. Printing is shifting left and right every 13.57mm. That is to say, a vertical line will print 13.57mm down, then shift 0.5mm left for the next 13.57mm then back to the original position for the next 13.57mm and so on all the way down the page.
This only happens when printing with the pigment black cartridge. Printing in colour, everything is aligned properly and vertical lines are perfectly straight. Printing a colour pattern in greyscale results in the misalignment. The phenomenon occurs with the USB connected computer running Windows XP, a 2 separate wirelessly connected computers running Windows 7. It also occurs when printing built-in templates from memory. or making a black copy.
It is not discernable in the nozzle check print, but the PGBK portion is 13.57mm tall and does appear to be approximately 0.5mm offset to the right compared to the colour bars printed below so I suspect this misalignment is exactly the height of the printhead. Printing in high quality mode results in wide (doubled?) vertical lines.
I have tried running the automatic alignment and the manual alignment functions. I have tried wiping the encoder timing strip with an alcohol soaked q-tip as described here: https://support.usa.canon.com/kb/index?page=content&id=ART109213&pmv=print&impressions=false&viewloc.... (although I would think that would affect both black and colour printing).
I think the printing is offset depending on direction of printhead travel. But I don't understand why it would affect black printing only unless colour printing is unidirectional?
Any suggestions? Something loose? Needs adjustment or tightening? Any way to force the printer to print unidirectional?
