I had my power supply experience a catastrophic failure (distinctive crack and electrical discharge noise, electrical burning smell) not long ago. It had been in use for over two years before failing (all components are roughly that age except the mobo; that was replaced with an RMA about 6 months ago after a failure).
Assuming it was just a PSU failure, after getting and installing a replacement, I went about stress testing to ensure the new PSU worked. It did - for about an hour. The same failure experience - I managed to see visible sparking from within the PSU this time. I was monitoring my internal temperatures and they seemed appropriate.
I made the mistake of using the same power cable rather than the new cable for the PSU, but in other testing that cable seems to be alright. I did take a 400W+ PSU and hook up the motherboard, CPU, and a hard drive and let it run for a few minutes - no failure there, but it's a significantly fewer number of components, and no load.
What other actions can I take to debug the potential issue with my build?
The RAM has since changed to 8GB of Ripjaws DDR3, but I am unsure of the model.