Dell 1720/dn Mono Laser Printer - Manual (Page 30)

7. Install the toner cartridge assembly into the printer by aligning the blue arrows on the guides of the toner cartridge
with the blue arrows in the printer and pushing the toner cartridge assembly as far as it will go.
8. After you replace the imaging drum, you should reset the imaging drum's counter. To reset the counter, press and
hold the Cancel button until all lights flash in sequence.
9. Close the front cover.
Cleaning the Printhead Lens
1. Turn off the printer.
2. Open the front cover by pressing the button on the left side of the printer and lowering the cover.
3. Remove the toner cartridge assembly from the printer by pulling on the toner cartridge handle.
NOTE: Do not press the button on the toner cartridge assembly.
NOTICE: Resetting the imaging drum's counter without replacing the imaging drum may damage your printer
and void your warranty.