Brother HL-5240 User Manual page 77

When you replace the drum unit with a new one, you need to reset the drum counter by completing the
following steps:
a
Make sure that the printer is turned on and the Drum LED is blinking. Press the front cover release button
and then open the front cover.
b
Press and hold down Go for about 4 seconds until all the LEDs light up. Once all four LEDs are lit, release
Go.
Improper Setup
Do not reset the drum counter when you only replace the toner cartridge.
c
Take out the drum unit and toner cartridge assembly.
6. Routine Maintenance
69