Canon MX720 Series Online Manual page 100

If the problem is not resolved after cleaning the print
Step 3
Clean the print head deeply.
From the machine
Cleaning the Print Head Deeply
From the computer
Cleaning the Print Heads from Your
Computer
Note
When you have performed the procedure until step 3 and the problem has not been resolved, turn off
the power and clean the print head deeply again after 24 hours. Do not disconnect the power plug
when turning off the power.
If the problem is still not resolved, the print head may be damaged. Contact the service center.
When the Print Results Are Not Even such as the Ruled Lines Are
Misaligned:
Align the print head.
From the machine
Aligning the Print Head
From the computer
Aligning the Print Head Position from Your Computer
head twice: