Not sure if this topic belongs here but here is where a power supply would be used. There are many computer power supplies being "junked" that are still very useful. It's easy to convert them to a high quality regulated (Lab) power supply to power MIDI boards etc. Check out http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply
Be VERY careful should you do something like that!!!!!! There's a couple of soda cans in there that could give you a shocking experience should you put your fingers on the wrong places. Always connect a light bulb to the different connectors in order to remove any power left in the capacitors.
You do not need to disassemble the PSU, you can connect the power terminals directly to the wires outside the PSU chassis. Won't be as neat looking though.
Hello Ed, I have been using one of these Power Supplies to feed all the Opto-Switches under all of my Keys and Pedals for years now, These optos work 100 % of the time perfectly, Thank you for the info, Works perfectly.