How to Reset Drum of Brother Mono-SFP DR1050?

1.    Open the top cover.

2.    Slowly take out the drum unit and toner cartridge assembly.

3.    Push down the lock lever (1) and take the toner cartridge out of the drum unit (2).

4.    Unpack the new drum unit and put the toner cartridge firmly into the new drum unit until you hear it locks into place.       If you put the cartridge in correctly, the lock on the drum unit will lift automatically.

5.    Put the drum unit and toner cartridge assembly back into the machine. Do not close the top cover yet.

6.    Press  4 times.

7.    Close the top cover.

8.    Make sure that the Error LED (!) is now off.