The below info is from Brother’s website, and pertains to replacing the drum cartridge in most Brother laser printers.

When your printer gives you an “out of life” error on the drum, you can either replace it with a new one, or follow the steps below to make the printer “think” you have replaced it so that you can get a little more usage out of your current drum (which is possibly not completely out of life at the moment you get the first error):

To replace the drum unit follow the instructions listed below:

The Brother machine has separate consumables the toner cartridge and the drum unit. Verify you replace only the drum unit and not the toner cartridge. If you want to know their difference, refer to “What is the difference between the toner cartridge and the drum unit?”

Do NOT use flammable substances or any type of spray to clean the inside or outside of the machine. Doing this may cause a fire or electrical shock.

Just after you have used the FAX/MFC, some internal parts of the machine are extremely HOT! When you open the top cover of the FAX/MFC, never touch the shaded parts as shown in the diagram below:

1. Open the front cover.

2. Remove the old drum unit. Place the drum unit on a drop cloth or large piece of disposable paper to avoid spilling and scattering the toner.

3. Remove the toner cartridge by holding down the lock lever on the right and pull the toner cartridge out of the drum unit assembly.

4. Wait to unpack the new drum unit until immediately before installing it. Place the old drum unit into the aluminium bag.

5. Re-install the toner cartridge into the new drum unit.

6. Re-install the new drum unit, keeping the front cover open.

7. Press the Clear key to display drum status.

8. Press 1 on the telephone keypad.

9. When the display shows “ACCEPTED”, close the front cover.

Discard it according to local regulations. If you are not sure of them, call your local Sanitation Department. Be sure to seal the drum unit tightly so toner powder does not spill out of the unit. When discarding used drum units, keep them separate from domestic garbage.