My pixma mp500 is skipping lines when printing

You will need to replace the printhead or buy another machine.

If you open the preferences option for your printer there should be a maintenance tab with easy options for cleaning and checking the results. The alternative is to use the menu directly on the printer: 1. Press Menu twice to show "2. Maintenance" 2. The first option is NOZZLE CHECK 3. Press OK This should give you a print showing the current state of each colour. If there are any missing lines in 3eBK or lines in any colours then perform the head cleaning below. 1. Press Menu twice to show "2. Maintenance" 2. Press + to show "CLEANING" 3. Press OK Repeat the nozzle check after each clean. If not improved after three attempts try a deep clean as below (cleaning uses up ink) 1. Press Menu twice to show "2. Maintenance" 2. Press + twice to show "HEAD REFRESHING" 3. Press OK Repeat the nozzle check. If still not printing correctly there are various external solutions available to clean the print head such as http://www.printheadhospital.co.uk/canon-hp-printhead-cleaning-kit.html

Do a printhead cleaning cycle.
This will remove the dried ink in some of the nozzles.
Printing should improve.

It is possible some of the nozzles of the printhead are clogged.
Do a couple of printhead cleaning cycles may help.

The printhead has clogged nozzles, in printer properties you can use the maintenance tab and try deep cleaning until a nozzle check print shows no streaks. When the nozzle check doesn't improve you need a new printhead.QY6-0059-000 around $50.00

Two things, usually the printhead is bad and needs replacement, QY6-0059-000, on rare occasions I've seen the purge assembly not cleaning and purging the black properly, and that happens. I would change the printhead first.

Yes, either it is plugged or it is burned out like a light bulb, most likely you need a new printhead, QY6-0059-010, around $50.00

Your printhead is plugged and needs cleaning. If you remove the inks and then the printhead, you can wet and fold a paper towel and just dab the printhead gently on the wet towel. When you see a solid black line on the paper towel your printing should be improved.

hmmm..can you do a test page to see if it's also the case?

http://tinyurl.com/6qcpgy

It sounds like the black tank/printhead is leaking. If it is, it'll be empty soon. New tank will solve that problem.