Hello to you rfsworth, and Welcome to the forums!
I saw your post about how you now have all new cartridges in your Officejet 6500A Plus and you are unable to print from Microsoft Word and when you make a copy, the black will not print. As you are describing, the black ink is not being printed out on anything except from test mode, which may be using the color cartridges all combined together to make a black. I suggest troubleshooting the guide below for this problem and hopefully the black will come back to life!
Printer Does Not Print Black Ink or Color Ink, or Prints Blank Pages
Tip: Plug the printer in directly to the wall outlet, avoiding power bars and surge protectors. This ensures the printer is receiving full power and may help this situation.
Please let me know the outcome!
Good luck!:)