Won't print because we had a huge hailstorm that cut off the computer and the printer and everything else for a day of two. The computer came back on fine, but the printer, if I turn it on, will not stop flashing all four lights at once, for ready, paper, drum and toner. If you punch ready, only toner will show, continuously, but take your finger off of ready, and all four flash again. What does this indicate? toner, or something else?

1. Background
   • HP provides details of the problem on its website. The problem usually occur on PC laptops or when printing across a network. HP offers several fixes for the problem.
     
   Software
   • First, check your Windows print queue and ensure the printer is not set as "Paused" or "Working Offline." This can often clear the problem and resume your printing.
     
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   Resolution
   • The problem can also be caused by printer driver issues. Try uninstalling and reinstalling the printer driver. Connecting your printer directly to your computer using a parallel cable may solve the problem, but this may not be practical in all cases as many modern laptop computers do not have a parallel port.
     

Instructions

1. • 1 "Power Cycle" Your printer. Shut down the printer, unplug the power cord from the socket, give it 5 minutes, plug it in again and turn it back on. Try to print.
     
   • 2 If the printer still won't process a job, shut down and restart your computer.
     
   • 3 Check your printer cable connections to the computer.
     
   • 4 Check the printer for any paper jams, check the trays, and also pull out the toner cartridge and/or remove any paper jam, if you find one. Put the cartridge back in. Then try to print.
     
   • 5 If after completing the steps above, the printer is still not working, click "Start," then "Settings," click "Printers," and the printer folder will open. Make sure your HP LaserJet 5 is selected as the default printer.
     
   • 6 Double-click your printer, and delete everything from the print queue, canceling all the print jobs. Close out the queue.
     
   • 7 Right-click on your printer icon and make sure it's not offline. If it is, then click "use this printer online."
     
   • 8 Right-click your printer, and click properties. Make sure the right port is selected for your LaserJet 5 Printer. If you are using a parallel cable, you are most likely using an LPT port; if USB, then look for a USB connection in the list. If the port connection is correct, try to print again.
     
   • 9 It's still not printing? Click "Start," then "Control Panel." Double-click "Programs and Features" or "add or remove programs," uninstall your Laserjet printer software, and restart your computer.
     
   • 10 Insert your Laserjet software and driver disk. Proceed to reinstall your printer software and drivers. Then test the printer again. If it is still not working, you probably will have to seek professional assistance.
     

You need to uninstall the printer from your computer and then reinstall the driver.

If everything at the printer looks fine (test prints, and no errors on the display) I would de-install and reinstall the software. The DE-install is important, DO NOT just reinstall over the top of the current installation. Also I would reboot after I removed the software and BEFORE I reinstall it. It might be overkill but it won't hurt to be through.

I have the same problem. Everything on the printer is working just fine. It'll do a test page just fine, so everything's working right. The %$^ thing just won't print. It makes noise like it's printing when you give it a print job, but it spits out blank pages.

Turn the printer off.
Disconnect the AC power.

On your computer, click Start
Click Control Panel
Click Printers
Select the Dell Printer
Uninstall it
Restart your computer
Turn the printer on
Allow the computer to reinstall the device-device for the printer.
Print a test page.

This is a huge problem, not only with the MFC-7420 printer, but literally every printer known to exist! The best way to solve this problem is to look at where the printer is connected. If it's connected to your computer, it may be trying to print something from there still, causing the information that the printer is receiving to become jumbled up and confused. I'm going to go step by step to try to help you out of your printer misery:

First: Unplug the printer from your computer entirely. Then unplug your printer's power source.
Second: Re-plug back in your printer's power source, and wait for it to turn on fully.
Third: Double check to make sure everything is working fine aside from the non-existent "paper jam."
Fourth: Re-plug back in the printer to the computer, and cancel all scheduled prints that are queued on your computer.
Lastly: Retry printing!

Hope this helps.
-Anonymity

It's the waste ink getting on the exit rollers instead of going where it should. Canon has a mod for that where you remove the print engine clean the rollers and exit and install a mylar shield so it can't happen again. Probably too big a job for you to do at home..messy too.

Reinstall the printer software.

I'm suspecting a faulty driver. Try searching " (model number) Motherboard driver".