Brother MFC-9870 - Reset Drum
After changing a DR6000 drum unit in a Brother MFC-9870, the printer’s page count needs to be reset. This will turn off the drum warning light on the printer.
Simply open the front cover, press the "clear" key and then press "1" to reset. Close the front cover.
Brother MFC-9870 - Change Toner Cartridge
Youtube Video: Change Toner Cartridge