PC won't boot with higher wattage PSU... but will with a lower one. Help?

I am at a loss.

This past month, I built a new PC. The build was as follows:

The build itself went smoothly, and I installed Win7 Home Premium 64bit on the system and ran it with no problems for about a month. And then, one afternoon, when I went to turn the PC on... nothing. The Power Switch LED flashed for a second and the fans briefly powered up... but then it all cut out. Another press of the Power Switch didn't even yield that much. (Although, if I shut the PSU off at the back of the PC and then turned it back on and tried again, I would get the fraction of a second power up.)

So, I set to work investigating. (After resisting the very strong urge to punch a wall or ten. >.>) Thinking it might be the Power Switch, I tried jumping the pins from the MoBo directly, to no effect. (Although I might not have been doing it right.) Next step was to test the PSU itself. I tried the paperclip test with the PSU plugged in only to a fan, and even that wouldn't work. So, the PSU was starting to seem the culprit. The final nail in its coffin was when I pulled an old 500W PSU from an old PC and plugged it in, and the PC booted up just fine. The Corsair PSU got sent back for a refund, and I went ahead and ordered a new PSU (as some further research revealed this seemingly happened frequently with this particular Corsair unit).

Cut to today. My new SeaSonic X Series X-850 PSU shows up, and I, happy camper, go to install it into my PC, thinking all of my problems are going to be solved. Wrong. Get everything plugged in, and the system, once again, won't power up. I get that brief LED flash and the tiniest bit of fan spinning still, and then nothing. (My walls are starting to look like very tempting targets again.) So, I swap out the PSU for the old 500W one again, and the PC boots up just like normal.

I am at such a loss here. I almost feel like this is similar to when a breaker gets tripped when too many appliances or what-not are all plugged into an outlet and being used at the same time. And yet, the PC worked just fine with the 600W PSU for a month. I'm not sure what could have happened to change that. I tried a couple of different outlets even, one plugged into a heavy duty surge protector power strip, the other not, but still the same thing -- the 600W and the 850W PSUs won't start the PC, but the 500W one will. (The 500W one is an Ultra XFinity, btw.)

Sorry for the novel, but I don't know what other steps to take here, what else to try to troubleshoot... and I figure the more info I supply to others, the better.

Thanks for reading and, hopefully, for any help you might be able to provide!
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More about boot higher wattage psu lower
  1. Looks like you got a DOA Seasonic. It happens.
  2. I forgot to mention, but the green light on the mobo does light up each time any of the PSUs is turned on... isn't that a signal that the PSU is working to some extent?

    I suppose it could be just horrible luck that got me a DoA SeaSonic after my Corsair died off, but I'm hesitant to go through this whole return process yet again only to wind up in the exact same spot with yet another PSU.
  3. Your 500watt lower quality one works the others don't, the board is modern so it is not a compatibility issue.
  4. Would a DOA PSU still cause that fraction of a start-up (with the brief fan spinning and LED light flash)?

    Sorry for all of the questions. I'm just trying to make sure it really is dead before I go through returning yet another PSU. Thanks for the answers!
  5. Looks like it and I am presuming you are connecting them the same way. Just one thing I thought of, the 500 watt has 4 pin CPU connector and works? If so the others have 8 pin and you are plugging them all in, have you tried just using 4 pins like the 500watt?
  6. You might have lost me there. (Some of this stuff I know well enough; a lot of it I'm still learning.) Between the 500W PSU and the others, the only difference when it comes to plugging the PC's components in is that the 500W one doesn't have all of the necessary connections for my newer video card. But, even on the older video card I swapped in to test with, the newer PSUs still won't work. Everything else hooks up with all the same connectors, though.
  7. Well I was referring to the CPU power connector on the board, older std is 4 pin the newer is 8 pin, your board has 8 pin connector and you are hooking up all of them the same way?
  8. Yeah, everything is being hooked up the exact same way between the 500W PSU and the higher ones. No differences there, I'm afraid.
  9. Best answer
    Then I am pretty sure your top tier PSU came DOA.
  10. Starting to seem that way. =/

    At any rate, thanks for all of the answers and help! Much appreciated.
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