Check the purple wire first (a.k.a. "so that's how my computer died")
September 25, 2009
So the power on my CNC machine was going to come from a computer power supply, and I had a recently decommisioned computer lying around. Instructables and other sites have some good instructions on "ATX power supply to DC" and "ATX power supply to lab power supply" (search strings). After wiring the thin orange to the thick orange, and the thick green to black, and a red wire to a "sandbar" load resistor, I thought it should be working. After all the changes, I still did not even have 5V coming out of my purple "standby power" wire.
Eventually I remembered something about that computer and how it had come to be in pieces and used for parts: one day about a year ago it just didn't turn on, and I thought it was because the power supply died. I think I confirmed my speculation.
Lesson learned: On an ATX supply, test the purple wire first.