Possible PSU Problem

[ekuest]

specs in sig. i made a thread in general computing a couple days ago, but i think i narrowed it down to a power problem so i thought id mosey on over here and see what you guys think. my computer recently wouldnt wake up after being asleep for a few days, so i hard powered it off and then tried to turn it back on. when i tried, the first time the computer would squeak and the fans would twitch, but it wouldnt turn on. any subsequent attempts would result in no noticeable attempt to power on. if i turned off the switch on the psu, turned it back on, and then tried to power on the computer, id get the squeak and the twitch like before, and then nothing after that.

i unplugged my video card (the 5870) and then the components would power on, but of course no display since there was no power to the gpu and theres no onboard gpu with an i7. so, since it powered on without the gpu load, i assumed that the problem was that the psu wasnt supplying enough power for the computer. this doesnt rerally make sense to me, as the same psu has been powering the same setup for almost 2 months now without a problem, but then finally decided it wasnt up to the task one day while in sleep mode?

so, what could have caused it to suddenly decrease power output, or the computer to increase power consumption, or something else that could be causing the problem? my 5870 uses 212W maximum, my cpu uses 95W maximum, and that leaves about 143W to spare at absolute maximum load on the cpu and gpu. for other power uses, i have a mouse and keyboard, 2 sticks ddr3, one 140mm fan, and of course the motherboard. im not sure how much they all use, but i cant think its over about 50W. so tallying everything up, i cant see why i would be maxing out my psu unless something got way overclocked, or the psu is putting out less power than it was a few days ago.

jonnyguru did a review of this psu, and had some safety feature worries, but said the psu overall performed up to its ratings, which include 432W on the 12V rail. so far my troubleshooting has led me to use an old 9400gt that doesnt need any pci power connectors, and the computer boots fine. now, i have decreased the voltage of the cpu by turning off 3 cores and HT, and undervolting it to .7V. hopefully that will be enough to let me plug in my 5870 and see if it maybe got overclocked on accident or something. my only other thought is to RMA it and see if a new one works, but i hate to RMA stuff unless i actually know that its broken. does anyone else have any ideas? thanks.

 

[plugwash]

IMO the most likely explanation is that something has failed in a way that dramatically increases base power draw (failed capacitors for example often act as resitors) and/or dramatically decreases the efficiancy of power conversion. That something may be inside the PSU or it may be in another component.

Do you have another graphics card of similar power consumption to the original card that you can test with?

 

[ekuest]

nah i only have these two cards. :/ think it's worth it to RMA my 5870?

 

[ekuest]

success! it was the 5870. i tried it in my friends computer, and let a lot of the smoke out. i pinpointed the bad cap on the card, which is good news. i can rma my gpu, but dont have a warranty on my psu. im quite pleased with the st45sf actually, as it wouldnt start my computer once the cap went bad. my friends psu, which is a lower-tier ultra X4, didnt engage any safety features telling it not to start, and tried to start with the bad cap which made a pop and some smoke. at least it helped me pinpoint the error. i just mailed my card off to be RMA'd right now.