Brother HL-3170CDW - Manual (Page 153)

Routine Maintenance
147
4
Cleaning the drum unit
4
If your printout has white or black dots at 3.7 in. (94 mm) intervals, the drum may have foreign material, such
as glue from a label stuck on the drum surface. Follow the steps below to solve the problem.
a
Make sure the machine is in Ready mode.
b Press a or b to choose Machine Info.. Press OK.
c Press a or b to choose Drum Dot Print. Press OK to print the drum dot check sheet.
d
Press and hold down to turn the machine off.
e Open the top cover until it locks in the open position.
f
The color of printed dots is the color of the drum you should clean. Take out the toner cartridge and drum
unit assembly of the color causing the problem.