Brother MFC 7550MC - Manual (Page 186)

REPLACING TONER CARTRIDGE AND DRUM UNIT
13-4
MFC 4550/6550MC/7550MC
OP-US-5.0
6)
6) Gently rock the toner cartridge
from side to side five or six times.
7)
7) Slide the new toner cartridge into
the opening on the right hand side
of the drum unit. To ensure that
the toner cartridge and the drum
unit fit together correctly, make
sure that the toner cartridge guide
bar is exactly aligned with the
guide slot in the drum unit.
8)
8) Gently turn the lever on the toner
cartridge backward until it stops.
9)
9) Reinstall the drum unit into the
machine and close the top cover.
Then, turn on the power switch or
plug in the power cord.
Toner cartridge
Drum unit