You must start the drum unit replacement procedure by opening the front cover of your Dell Black & White 1720 monochrome laser printer. Important: Any excessive exposure of the new drum unit or the toner cartridge to direct sunlight or strong artificial light will lead to future print quality problems. It is always better if you keep a spare/new drum unit for your Dell Black & White 1720 monochrome laser printer in stock, but please store this consumable component on a pallet or shelf in a storage room with temperatures lower than 40degreesC/104degreesF (the recommended optimal temperature is 21degreesC/70degreesF) and 40% relative humidity. The only available action is the installation of a new drum unit. Please note that all print operations are disabled in this situation.  The and the LEDs are blinking – This signal indicates a non-operational printer's mode, caused by a completely exhausted drum unit. Therefore, you should install a new drum unit soon after the initial appearance of this warning signal. its print resource has been 99% consumed/exhausted.  The LED is blinking – This is an advance notification, which indicates that the installed drum unit is near the end of its useful life, resp. Please install a new drum unit, if any of the listed and described below signals appears. The precise built-in system of your Dell Black & White 1720 monochrome laser printer is constantly monitoring the status of the installed drum unit, and it will notify you when this important consumable component needs to be replaced.

Toner for dell 1720 laser printer