http://www.instructables.com/id/Conv...gular-DC-Powe/

i did it with a old one i had.

Mine had 2 12v rails and i made sure that 1 rail powered on set of output plugs and the other rail another.

Mine read a little low with only one resistor applying a load, so i added another resistor and bumped it up, now I have 12.3v i think.