Canon pixma mp780 printing problem

If deep cleansing via software doesn't work then you've got to manually clean your print head unit. Sometimes you'll have to bite the bullet and get a replacement print-head unit ($$). If you're at the stage that you're considering replacement, then you've got nothing to lose by cleaning the print-head unit yourself. It's simple. Remove all ink cartridges first then remove the print head itself. Place the print head unit in a saucepan of warm (NOT boiling hot) water and leave to soak for an hour. (Protect your clothes - it gets messy) After an hour, flush the printhead unit under a running tap. Don't run the water too fast or you may damage the unit) You should flush until the water runs clear. Do not attempt to clear the nozzles with anything other than water - they are very fine needle jets and you will damage them!! If needs be, return to saucepan and leave to soak in warm water again and repeat process. When you are satisfied that the printhead is clean, you need to dry the unit thoroughly. Shake as much water from it as you can then pat it gently dry. Next place it on some absorbant kitchen paper and put the unit in a warm place to thoroughly dry (Overnight in a warm airing cupboard would be good). Once dry, refit the unit put in (Preferably new - but I've used existing one's without problem) cartridges and run a cleaning cycle. Your printer should now work as if new!!! - In Most cases!! - sometimes though, you'll either have to replace the print head unit - which sometimes can be more expensive that simply replacing the printer. What have you got to lose though eh? CLIVUSS

Try replacing the color cart. with a NEW one.

Hope that helps...

Geno