New power supply burning smell?

I put upgraded my new computer with a new PSU to power a 5770, I've upgraded a few pc's in the past and have so far upgraded 3 psu's. Everytime I upgrade there always seems to be a burning smell coming from the new psu and it is also coming from my latest one. I've upgraded to a corsair 650w so it's no lousy quality psu. Anyone else ever get a burning smell from new psus? I'm kind of worried that the 3 that I've upgraded might be faulty. Also all 3 were corsairs.

Nope, never got a burning smell. Did get a piece of wrapping plastic twig stuck on the fan though, made a buzzing noise until I finally got it off a week after purchase. >.>

My old motherboard ate PSUs like my old '81 Riviera ate altenators. Probably poor grounding through a manufacturing or engineering error.