Power button not working

The power had been getting flaky, then it quit working altogether. When I removed the front panel, I found a black wire near the power button that wasn't connected. It doesn't have any solder on it so I don't know if it was ever correctly connected. Where does this wire go?

When I checked the power button with an ohmmeter, the contacts close when pushed in. Without opening the whole unit, I don't know where to check voltage from. What voltage is on this button? If I touch the contacts with the red and white wires, the unit comes on. Any assistance would be appreciated.