Canon MultiPASS C50 Service Manual page 53

Hold the BJ cartridge by its sides only. Do not touch the print head, the
sharp edges around the print head, the silver plate on the bottom of the
Caution
cartridge, or the silver metal or circuit area on its side.
PRINT HEAD
Make sure the BJ cartridge holder is in its home position (on the
right side of the unit) when you are not using the MultiPASS C50. If
it is not in its home position, press the CARTRIDGE button.
Leaving it out of its home position will dry out the print head on the
cartridge.
Clean the print head when print quality is no longer satisfactory. See
"Cleaning and Testing the BJ Cartridge Print Head" for instructions.
If the print quality does not improve after five consecutive
cleanings, replace the ink tank or BJ cartridge.
Do not use a BC-21/21e Colour BJ cartridge with either of its ink
tanks missing. Doing so can cause it to clog.
Do not remove the ink tanks from the BC-21/21e Colour BJ
cartridge unnecessarily, or the ink in them may clog.
Never attempt to refill an empty cartridge.
Chapter 1: General Description
1-33
IB2-28