Canon CR-55 - Manual (Page 53)

Regular Maintenance 49
Magnetic Heads
Cleaning the Magnetic Heads
If the magnetic heads are dirty, MICR characters cannot be scanned correctly.
Periodically clean the magnetic heads with a commercially available audio
head cleaner.
1
Hook your finger around the open lever and open the maintenance cover.
2
Clean the magnetic heads with a commercially available audio head cleaner.
The magnetic heads are on the maintenance cover in the location illustrated
below.
3
Gently close the maintenance cover until it clicks into place.