Speckles on one side of printed paper

[JBR10]

We have tilted backwards this printer in order to remove a jammed sheet of paper from underneath, which we managed without any problems. However, the next time we printed a letter in black, the sheet featured blue speckling all the way down one side of the front of the sheet.
Printing documents entirely in another colour, for example dark blue, produces acceptable results which will do for now, but attempting to print in black comes out with the blue speckling.
The printer is no longer under warranty.

We could, of course, buy another black cartridge in the hope that this may solve the problem, but as we all know they are expensive things!

Can anyone offer any suggestions to help sort out this problem, please.

 

[Repairatrooper]

If you are getting blue speckles then your issue is likely with the cyan cartridge and not the black. Remove the cyan and check closely to make sure that nothing has become lodged in the cartridge. 

[JBR10]

Repairatrooper, thank you for your help.

The Cyan cartridge occurred to me too, but the thing is that these 'blue' speckles only occur when I print a page completely in black.

As I needed to print off a letter urgently, I then saved it in dark blue lettering and printed that.  No speckles!

I have also looked at all four cartridges and can see nothing lodged in the cartridges.

I would like to rotate each cartridge roller to check all the way around, but they seem to be locked in place.  Perhaps there's something somewhere to release them.

I also read elsewhere that a heated roller (can't remember what it's called!) which actually prints the image on the paper could have been damaged when we removed the jammed paper.
If the problem lies with the black (or cyan) cartridge, at least I can replace that, though they are expensive.  If it is some other component a repair might be necessary which means we'll be unable to print anything for a while.

[JBR10]

I apologise for not responding yesterday, as I was in the hospital for a large part of the day and couldn't find time to follow these suggestions.

I have now printed off ten sheets, each containing only a single black full stop.  Unfortunately, the speckling (which is definitely blue) is exactly the same on all ten.  I also did the same with a mid-blue full stop and out came a clear sheet of paper.

There is something strange here.
Going by the fact that other colours print correctly, would you suggest that I buy a new black cartridge and hope for the best, or are there any other ideas I could try?
Thanks again for all your help.

[JBR10 · Accepted solution]

Thanks for the help.  I have decided to take the printer for repair by someone who knows what they're doing, as I can't trust myself not to make matters worse!