Hi Gary Brooks, I would be happy to do all I can to help you with your C6280. I understand it will not turn on, and the adapter light is illuminate until you connect the cable to the printer. Please review the following document to ensure you have completed all of the necessary troubleshooting;
HP Printers The HP Printer Does Not Turn On or Respond When the Power...
Also, do you have the printer power cable connected directly to a wall outlet or is it in a surge protector or power bar? Even if you have been using a surge protector/power bar all this time and you feel it is not the cause, please connect it to a wall outlet just so we can eliminate the power source as the root cause. Issues when Connected to an Uninterruptible Power Supply/Power Strip/Surge Protector
In this document you will see, ISSUE: Problems or issues may arise when an HP LaserJet series printer is connected to an uninterruptible power supply (UPS), a power strip, or a surge protector
^ This is not limited to Laserjet printers.
I hope this helps. I work on behalf of HP.