All the lights on my Dell 1720 printer are flashing

SOURCE: Dell Printer 1720

This error is caused by the the flap on the right hand side of the output tray (the tray the paper feeds into once it has printed). It becomes stuck in the up position and sends a false positive error to the printer. One "work around" for this is to tape a quarter to the plastic flap. This keeps the flap in a down position, thus negating the false positive. The other option is to call dell laser printer tech support to get it fixed. <If it is still under warranty>

SOURCE: 1720 Dell Laser printer Photoconductor Problem

I finally figured it out (with Dell Tech Support's help)! When you replace the drum, you MUST reset the counter as well. All you have to do is:

1) Turn off the power using the switch on the back of the printer. Open the front door of the printer.

2) Hold Continue button down, power on the printer, and continue to holding Continue down until the LEDs begin to flash. When the LEDs start to flash, release Continue button. The LEDs will continue flashing until only Error LED will be lit.

3) Close the front door. Continue, Ready/Data, Toner Low and Load Paper LEDs should be lit.

4) Wait till the printer completes the POST process. POST is complete when fan noise and rollers stops. After POST wait for 5 seconds

5) Press Cancel button 4 times slowly until the Toner Low LED is lit. This is the procedure resetting the counter.

6) Press and hold Continue until all LEDs begin to cycle in sequence, then release Continue. Now only the Toner Low LED will be lit.

7) Cycle the power of the printer (turn it off and then back on).

GOOD LUCK, EVERYONE!!!

SOURCE: Dell 1720 DN- all lights

try to turn off the printer, remove the power cord, then press the power button for about 5 secs. plug it back, turn it on. If same thing, press the cancel button for about 10 secs. if still the same, try to check the cartridges, remove them and make sure they are not yet empty, shake them a few times, then connect them back. Make sure no paper jam as well.