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?
GIGABYTE Ultra Durable VGA Series GV-R685OC-1GD Radeon HD 6850 1GB 256-bit GDDR5 PCI Express 2.1 x16
Crucial RealSSD C300 CTFDDAC064MAG-1G1CCA 2.5" 64GB SATA III MLC Internal Solid State Drive (SSD)
ASUS M4A87TD/USB3 AM3 AMD 870 SATA 6Gb/s USB 3.0 ATX AMD Motherboard
G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-4GBRL
Western Digital WD Black WD5002AALX 500GB 7200 RPM 32MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive
AMD Phenom II X4 965 Black Edition Deneb 3.4GHz Socket AM3 125W Quad-Core Processor HDZ965FBGMBOX
Rosewill CHALLENGER Black Gaming ATX Mid Tower Computer Case, comes with Three Fans-1x Front Blue LED 120mm Fan, 1x Top 140mm ...
ASUS PCE-N13 PCI Express 150/300Mbps Transfer/Receive Rate Wireless Adapter
ASUS DRW-24B1ST/BLK/B/AS Black SATA 24X DVD Burner - Bulk - OEM
The RAM has since changed to 8GB of Ripjaws DDR3, but I am unsure of the model.