I just got a new PSU to replace my old one that smoked itself out. My system specs are as follows:
AMD Phenom II X4 810 2GB memory Pretty standard Gigabyte MB CD drive WD Caviar Blue HDD Sapphire Radeon HD 4890 Corsair TX650M PSU
I previously had a 700W OCZ StealthXStream.
Here's the current situation:
A little while ago, the OCZ PSU burnt itself out. I quickly turned the machine off and unplugged everything, then checked the system sans graphics card with my old Antec Earthwatts (using onboard graphics, since the Earthwatts is 430W and can't power my graphics card). The system booted fine. I received my Corsair PSU a couple nights ago, and put everything back together and powered it up. The graphics card fan spun up to max speed and just stayed there, and there was no video output from it. There is video output from the onboard graphics, and the system boots fine but Windows doesn't detect the Sapphire card.
I then re-seated the card and re-plugged the power cables into the card and PSU, and voila! everything worked! Video came out of the Sapphire card and Windows detected the Radeon HD 4800 series card.
Fast forward to the next night when I get home, and when I turn the computer on now, it's gone back to its former state of graphics card fan spinning all the way up, with video out coming only from my onboard graphics. I've tried re-plugging things in to no avail. What I don't understand is why it would have worked once the previous night and stopped working now. I can provide more exact specs to my system if needed.
And while I'm here, is there any way to test the power supply and make sure that the 6-pin PCIe connectors are supplying the right amount of power using a voltmeter?
TL;DR: Graphics card fan spins at max speed when system powers on, video only comes out of onboard graphics.
UPDATE: So, I've tested my GPU in friend's computer; works perfectly. I then tested his GPU in my computer (they're not the same card, but I just wanted to make sure that my motherboard PCIe slot wasn't fried) and lo and behold, it worked! I then plugged my GPU back into my system, and it worked! This was with the HDD and front USB/IEEE/audio connectors disconnected. I then went and plugged in the HDD and booted again with success. Then I plugged in the front USB and IEEE (these are the case USB/IEEE connectors into the motherboard) and it failed again.
I now can't get it to boot at all again, with the same symptoms as before. I have NO IDEA why it will boot sometimes, but then refuse to boot other times. I know my parts aren't faulty; I've probed my new PSU and tested my GPU/PCIe slots, but still it complains and won't boot up. Any help would be appreciated!