Several loud popping noises

We have been in the mist of switching rooms and our xbox has been sitting outside with some other stuff for about 2-3 weeks now. We've now finished and brought it inside just for the xbox to make several loud popping noises after being plugged in and continue until being unplugged. There's definitely a smell, and a little white smoke that seems to emit from the cpu side of the device. However, I've teared it down, no blown fuses or resistors on the motherboard or even char marks on the chassis. Wondering if it may just be the psu is bad, or if it's something else since it's several pops and I can replicate it by plugging it in again?