Brother HL 1240 - B/W Laser Printer Service Manual page 150

CHAPTER 6 TROUBLESHOOTING
I-24 Toner specks
User Check
(1) Check the paper used meets the recommended paper specifications. A rough
surfaced paper may cause the problem.
(2) The toner cartridge may be damaged. Install a new toner cartridge.
(3) The drum unit may be damaged, or may be nearly at the end of life. Install a new
drum unit.
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