Canon Pixma ix6850 won't print black although prints perfect nozzle check pages?

[CAT00]

Hi all,

I am using an ix6850 to print black transparencies for screen printing, never had any problems before. Then half way through a print it stops printing the jet black i need, I replaced the small black cartridge because it was spent but it won't print black from photoshop or illustrator only if I do a nozzle check does it print jet black, perfectly. We've messed around with colour profiles but nothing works. I'm begining to think it isn't a problem with the ink cartridge itself but a problem between the cartridge and the actual printing bit ( no idea what it would be called ) as when the printer was left overnight it printed a bit of the halftone before it gave up and returned to grey?

Just to add I've just discovered it can print jet black if it thinks its doing it on plain paper. It just won't do it in any of the usual modes for glossy paper?

Any idea what we could do?

Cheers,

Cat

[CAT00]

Wow thank you for such a clear everything! I think I understand what you are saying. All the test sheets and nozzle check sheets came out fine as far as I can remember but in light of what you have said I'll run them all again. You are right, it sounds exactly like the same sort of problem and would explain things rather neatly. Im not a technical person and have very little time on my hands (exhausting young children) so I've just made do with printing fainter transparencies which ultimately will make it impossible to create the silkscreens I need further down the line so does need to be dealt with at some point. So thank you I will look into it and see if I can anywhere!