Question about Canon PIXMA MP780 All-In-One InkJet Printer

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Canon Pixma MP780 print quality fault

I have a problem with my MP780. I've tried all of the maintenance steps in the manual but I still have a white horizontal line every inch or so, almost like the paper feeder is slipping forwards by 2mm. If I print high quality, the print becomes blurred / slightly smudged every inch or so. When I print the nozzle check, the first 6C band is two tone, split exactly 50/50. I've tried changing that cartridge and deep cleaning. I've also done auto and manual head alignment but nothing fixes the problem. When I try the manual head alignment, the B setting is like a large toothed comb i.e. each block is solid at the top half (to varying degrees of quality) and there are 10 blue and 10 white bands in the bottom half of every block.

The printer is 43 months old. Is it worth repairing?

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  • eschofiel421 Aug 29, 2008

    I've also started experiencing this problem last night after changing my black ink cartridge (3e). I did cleaning, deep cleaning and nozzle check and the black results lead me to believe it was clogged. Gave up on it last night and tried again today and the nozzle check and alignment are all find today. However I'm stillg getting the white horizontal lines. All other colours appear to be fine. My printer is 38 months old.

  • porroh Aug 30, 2008

    Just to add to my previous post, I tried printing some test sheets from www.systeminsight.co.uk. This should print a page of solid colour / black to test each of the ink cartridges.



    Every colour, and the black ink, prints with alternate lighter and darker bands. Each clolour / black band is about 3mm wide, and there are some white bands of different thicknesses.



    The order of the bands is as follows;

    2 colour (alternately, 1 lighter, 1 darker, approx 3mm each)

    1 thin white (approx 0.5mm)

    12 colour (alternately,6 lighter, 6 darker, approx 3mm each)

    1 thin white (approx 0.5mm)

    2 colour (alternately,1 lighter, 1 darker, approx 3mm each)

    1 thicker white (approx 1mm)

    12 colour (alternately,6 lighter, 6 darker, approx 3mm each)

    1 thicker white (approx 1mm)

    2 colour (alternately,1 lighter, 1 darker, approx 3mm each)

    1 thicker white (approx 1mm)

    12 colour (alternately,6 lighter, 6 darker, approx 3mm each)

    1 thicker white (approx 1mm)

    .....then the whole sequence repeats



    Perhaps the white bands might be caused by the paper feeder not operating accurately and the lighter and darker bands could be a blocked ink head but I'm not an expert so am just guessing. The paper feed makes some unusual noises.

  • porroh Sep 01, 2008

    Thanks for the feedback. I tried that but it hasn't improved the print quality. If anything it's slightly worse because each of the darker colour bands in the test print now has a 0.5mm ligher band in the middle of it, and the frequency and width of each of the white bands has changed. They're narrower which is good but there are now more of them which is worse. I suspect that the print head needs to be replaced but the paper feed may also be contributing to the problems. Close examination of the rollers shows that they are exhibiting what might be the early signs of the rubber perrishing.



    I can get a new print head for £65GBP but given that the paper feed is becoming less reliable. I've already wasted almost a full set of print cartridges trying to fix the fault and there is a risk that buying a new print head and a full set of cartridges may not solve the problem.



    As the cost of the repair will most likely exceed the price of a second-hand but fully serviceable printer of the same age, I'm thinking that it might be a safer bet to just scrap the printer and buy a new one.

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My daugther also has a Pix780 so I just replaced my print head with hers and now the colour prints great. I guess I'll try cleaning mine first and if that doesn't work, I'll purchase a new one when the dealer who services Canon opens on Tuesday. I could also buy one from the Canon website for something like $60. I copied the following from Canon's sites under the FAQs. Sounds like you may need to replace your printhead.

How does a Canon Printhead work?
The printhead delivers very small drops of ink onto the paper. The ink from the cartridge is transported via small tubes. Heating elements heat the tubes, creating a small bubble of ink. The heating element determines the size of the drop to be applied to the paper.

How do I know I may need to replace my printhead?
There are a few symptoms that may indicate printhead failure or a clogged printhead. If the following symptoms continue even after replacing the ink cartridges and trying the troubleshooting steps in your user's manual or those listed below, you may need to replace your printhead:

  • Pages come out blank, or you see poor print quality
  • Pages you print appear to be missing colors
  • Colors on the printed page are quite a bit different from what shows on the screen
  • Horizontal white lines or light-colored lines or light streaks appear throughout the page

Why would the printhead have problems?
After hours of printing, the heating elements may fail after being turned on and off hundreds of thousands of times. The printhead can also become clogged or blocked with paper debris or solidified ink. If your print quality is poor or your printer will not print at all, it may be time to change your printhead.

Posted on Aug 30, 2008

  • eschofiel421 Aug 31, 2008

    I clean the printhead using the methodogy recommended by Daniel 19 posted June 27/07 to a question where the black ink stopped printed althought. Anyway, if worked for me and everything prints great now. Here are his instructions.





    I had the same problem I found this solution to be very effective:

    * Buy alcohol solution (70% or more). You can find it in any drug store.

    * Remove both cartridges from the printer head. Unplug the printer head from the printer body. Pour the alcohol into paper towel layer.

    * put the printer head on the top of wet towel with the face of HEAD touching the towel.

    * clean the head with the towel and get rid of all the built-up ink on the head.

    * Pour the alcohol into the printer head container (ink-receptacle area is where the ink cartridge normally sits, notice a small hole where the ink flow into the printer). Do not touch any electronic parts and let it dry over night.

    * Do step 2-5 again if necessary.

    * Install the cartridge back to the printer and run several head cleaning maintenance, print nozzle check, make sure to repeat this step until no more dead nozzle shown.

    It worked for me :0)

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