I also did the same thing, take a printer power supply. Mine was an Epson though. Look at the metal shields protecting the power supply, type the number you find on it and type in Google, +p/n +HP +repair , this will bring up links to PDFs that HP provides to the public, but designed for Printer repairmen. The PDF file includes a schematic of the Power supply and the rest of the printer. Hope this helps you in your venture. You usually can't find these PDFs on the companys site directly, thats why you have to use those search parameters. I guess they think the file will just confuse most people.