How to Reset a Canon MX850 to Its Default
The Canon PIXMA MX850 is a combination computer printer and scanner that is capable of producing full-colour photo images and copies. The networkable device prints at 4800 dpi resolution and produces borderless 4-by-6-inch photos in a little over 20 seconds.
Resetting the printer may be your best option if it suffers a software failure. Thankfully, performing a "hard" reset is very basic and only takes a few minutes to execute.
Turn off the Canon MX850 by pressing the power button on the top-right side of the unit.
Unplug the power cable from the power connection on the back of the Canon MX850 and the electrical wall outlet.
Remove the USB cable connection from the printer's port and the USB port on your computer.
Allow the printer to remain unplugged for 60 seconds, then reattach the USB cable and power cable to the printer.
Turn the printer back on by pressing the power button. The Canon MX850 is now properly reset to system defaults.