Studio 540 Power supply replacement

Hey people. I recently had a few power interruptions at my house and afterwards found my studio 540 would not turn on. Thinking it was the power supply, I replaced it. The computer powers up and everything works fine but after a few minutes it just shuts off like it lost power. Fans on CPU and case also seem to be louder than I remember and spin faster. Did I short something on the motherboard? Thanks for any help.