i have a desktop computer that had been working great with a 430w atx power supply for nearly 8 months. i upgraded the power supply to a Thermaltake with active PFC about 2 months ago and my headaches have started since then. For some inexplicable reason, I have blown about 4 power supplies. They seem to work ok in the beginning, but after 15 days or so, they blow up. I have not noticed any significant trend, but they seem to blow up if I turn off the power at the back of the PSU. I have a Belkin 1100uva with AVR UPS to protect my entire equipment. I don't think I am overloading my PSUs either. AMD X2 4400+ (Thermaltake Venus 12 cpu cooler @lowest setting) MSI K8T Neo-2 FIR 4*512 MB OCZ Premier DDR 400 ATI AIW 9600XT PCI Cards: Intel chipset modem CMD IDE raid card Promise IDE raid card Creative 24-bit live! SC 3-port IEEE card Hard Drives: 1*250GB WD 8MB (EIDE) 1*300GB Maxtor 8MB (EIDE) 1*200GB Maxtor 8MB (EIDE) 2*160GB WD 8 MB (EIDE-RAID) Fans: 2*80mm rear case fans 1*80mm 1700-4500rpm Venus 12 cpu cooler 2*120mm front case fans The power supplies I used were 1*(don't know brand) 430w PSU (worked fine for 8 months) 2*Thermaltake Active PFC 550w PSU (blown) 1*Logisys 550w PSU (blown) 1*Dynapower 480w PSU (blown) I think anything > 400w should be adequate for my rig, yet I can't explain the frequent blowups. I checked inside the PSU and there is no burning, not does the fuse seem to have burnt/destroyed. I have removed all the hardware and put it back again to ensure that there are no metallic objects shorting the motherboard. Can any suggest what might be causing this problem?

Check the voltage at the wall while under load.

The amperage on +12v rail is the most important consideration when selecting a power supply...just saying, "400w should be adequate" doesn't take amperage into account. Here's a few average consumption numbers: Your X2 CPU uses 89W or 110W, so it requires either 7.5A or 9.2A The board itself draws about 0.5A. HDD = 2A You have 5 drives, so 2 x 5 = 10A Optical = 1A You don't have any listed but I'm sure you have at least one, I'll assume 2A. Cooling fan = 0.25A You have 5 listed but you also have to include the PSU fan(s), so 7 x 0.25A = 1.75A Add em up: 9.2 + 0.5 + 10 + 2 + 1.75 = 23.45A...that accounts for 281.4W You shouldn't look for a PSU with just 24A on the +12v though, you should have a bit of a safety factor...say 25%, so now you're up to 29.31A. So 30A on the +12v is the minimum you should consider...that accounts for 360W. Even though the chances of running ALL +12v devices at the same time are slim, you should assume that you will. Better to have too much in reserve than not enough. The rest of the hardware (RAM, PCI cards, video, etc) pull the bulk of their power from the +3.3v & +5v rails. And most times, manufacturer's give the +3.3v, +5v, & +12v a combined wattage rating, so that has to be factored in as well. Also, the PSU should conform to the latest ATX12V 2.x spec which states that a single +12v line should not exceed 18A...so your PSU should have dual +12v rails of no more than 18A each. Some manufacturers exceed this, better manufacturer's have added a 3rd +12v rail when the amperage goes beyond 36A. Also, the spec states a hold-up time of 17ms minimum. The problem is, the spec is a "guide"...it doesn't have to be adhered to. In other words, there are a LOT of things to consider, especially when running a highend system with a ton of drives & cards. You can download a copy of the latest spec & see for yourself what a PSU *should* conform to: http://www.formfactors.org/FFDetail.asp?FFID=1&CatID=2

The two thermaltake psu (550w) I blew were certified for SLI rigs and as I mentioned I had a 430w PSU running for 8 months with no problems. All other PSU are rated for 550w+ (continuous load) with dual 12v rails. So my suspicion is that it is something beyond wattage that is causing this problem. Could something be suddenly surging among the devices? If I remember correctly all the PSU fail to boot when I shut down the PSU using the switch in the back of the PSU rather than through OS shutdowns (when the OS crashes, etc.).

When you say they're 'blown' does that mean they're completely dead? You might as well open one up and see if the fuse has blown. If so, most likely it's the input to the PS that's the problem. You have it going through a power strip and UPS. Try plugging it directly to the wall socket and see if they last longer.

Logisys is cheap crap & so is Dynapower...you got what you paid for. I can't comment of the 430W unit because you didn't provide a brand name. The Thermaltake 550W has dual +12v rails of 14A & 15A...but that does NOT necessarily equal 29A. It claims to be ATX12V 2.0 compliant but only has a hold-up time of 8ms. http://www.newegg.com/Product/Product.asp?Item=N82E16817104014

Two of these were blown: http://www.newegg.com/Product/Product.asp?Item=N82E16817153029 I could open only the logisys power supply and the fuse appeared to be intact (no burnt parts either, everything looked clean). One of the PSU's (Dynapower) was from Bestbuy and the geek squad technician mentioned that one of the lines (?) was not working.