Brother HL 4150CDN - Manual (Page 102)

Routine Maintenance
96
5
Replacing the toner cartridges
5
Before you replace the toner cartridges, see Before replacing the consumable items on page 92.
a Make sure that the machine is turned on. Press the front cover release button and then open the front
cover.
b Hold the green handle of the drum unit. Pull the drum unit out until it stops.
c Hold the handle of the toner cartridge and slightly push it toward the machine to unlock it. Then pull it out
of the drum unit. Repeat this for all the toner cartridges.