You can actually test the power supply before connecting it to the motherboard. Take a look at the power supply pinout by CLICKING HERE
. Jump pin 14 with 13, 15, 16, or 17 to turn it on. You will have to get a manual for your motherboard to see how the front panel connector is configured with your case power switch. If you have that manual you can jump the 2 connector pins for the power switch to test the p/s from the motherboard.