Hi jimwill48.
Power up the supply with a load on the 5v rail and test it with a meter, it either needed as a sense wire or not, your soon find out when you load that rail with the coral wire on or of in terms of current and voltage difference, try leaving it connected first, see what you get in voltage on the rails, i will post a link below on atx modded supply's
Please be careful with voltage inside, there is power stored in the high voltage capacitors when the power is removed.Although some have discharge resistors, some power can remain for 15 minutes or more. Dave.
http://web2.murraystate.edu/andy.bat...owersupply.htm