Brother HL-4040CDN - Manual (Page 133)

Routine Maintenance
124
6
c
Wipe the outside of the printer with a dry, lint-free cloth to remove dust.
d
Remove anything that is stuck inside the paper tray.
e
Wipe the inside of the paper tray with a dry, lint-free cloth to remove dust.
f
Put the paper tray back in the printer.
g
Plug the printer back in, and then turn on the power switch.
Cleaning the inside of the scanner windows
6
a
Turn off the printer power switch and then unplug the printer.