Our Officejet Pro 7780 is printing dark stripes over pages. I can see the document that I am trying to print on the page, but it is covered with large patches of dark ink and is barely visable. It was working fine when I manually printed the first page of the document (to confirm that it was working) then started printing the dark stripes when I attempted to print any page after that. I have changed no settings in the document or printer since I printed the first page.

Disconnect the electrical plug. Leave unplugged for a couple of minutes. Replug the machine and see if the printer has reset itself.

Does this happen when you print, or only when you copy? If you print out a configuration or user settings page, or print a page from the computer, is it also missing two vertical lines of print or is it only when you are copying?

If it happens when you print, you may need a cleaning, or you may need to replace the toner or drum cartridge. If it's an inkjet machine, there's a possibility there is some ink or grease on the encoder strip (a small belt-like plastic strip that goes through the print-head carriage).

If it only happens when you copy, test both the flatbed and the document feeder. If it happens on both then you may have a bad scanner. If it only happens when using the document feeder, you likely have some whiteout (or something) on the glass. When you make a copy in the flatbed, the scanner moves across your document. When you make a copy using the document feeder, the document moves across the scanner. In this case, if there is anything on the scanner glass (like whiteout) your copies will be missing a vertical line of print data (it could be white if there is whiteout on the glass, or it could be dark if something dark is on the scanner glass).

Usually you can lift the flatbed cover and look at the glass to see if anything is on it (usually at the left side of the scanner). Clean the glass, first with alcohol to remove the obstruction, and then with a little windex to remove anything the alcohol may have left behind.

You need to clean the drum When I was working for the City There was the same problem with the Laser printers. Check the Manuel and see if there is a page on cleaning the print drum on your machine. Also you may try Talking the cartage out cleaning there as well It seems you are picking this up form somewhere after the print My Guess would be the print drum? You may also have to replace the drum as well. I am guessing that this is a laser printer? if not then there are other solutions.

you have to replace the print cartridges with a nw genuine ones

to get to the root cause of the problem . you can try printing from the notepad and check it prints fine from the notepad . if it prints fyn then there can be some issues with the software compatibility.. which version you have for microsoft office.

Always try replacing the ink cartridges first.

It sounds like the print heads in the 7780 are bad. Don't confuse the ink cartridges with print heads. The cartridges fit inside the print heads. You will need to change the heads. Here is a link to HP's how-to.
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00841890&tmp_track_link=ot_faqs/top_issues/en_us/c00841890/loc:1&lc=en&dlc=en&cc=us&lang=en&product=2512010

Could have the same problem with the Dell.

clean your black cardriges and calibrate.

YOU WILL NEED DRIVERS FOR THAT DEVICE.

WWW.HP.COM/MAC
HP OFFICEJET PRO DRIVERS MAC 7780
OR
HP OFFICEJET PRO 7780 MAC DRIVERS
OR
HP OFFICEJET PRO 7780 DRIVERS

AND

CONTROL PANAL GO INTO NETWORKING AND SHARING FOLDER

PRINTING SHARING, OR PROPERTIES SETTING NEED TO BE CHANGED

DOES THE SYSTEM SUPPORT WIFI

MAKE SURE THAT THE ANTIVURAS PROGRAM AND FIREWALL IS HAS STOPPED YOU SCANNER TO COMMUNICATE WITH THE MACHINE, JUST SOME FINE TUNNING IN THE FIRE WALL MAYBE ALL IT IS.

ROD

Time for a new print head.

either roller is not cleaned or cartrige gone bad.