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After switch to HX850, system won't power on


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I swapped out my 3-year-old PSU (see below for why) for a brand-new Corsair HX850 from Newegg. Followed all directions and common sense in terms of unplug/plug order. When plugged in, the green MB power light comes on, and ethernet power lights are active. But when I press the power button, nothing happens; doesn't even pulse on for a second.


I double-checked that everything was plugged in and I hadn't dislodged any cards. I checked the power button connector and other pin connectors, and tried booting it over ethernet. I tried unplugging all modular cables from the PSU. I tried unplugging the 2x PCI-E connectors from the graphics card. Same result with everything.


The only difference I can think of is that the old PSU had a 3-pin MB connector for the PSU fan, and the HX850 doesn't. Just in case the MB somehow requires a PSU RPM readout, I plugged a case fan into that connector, but no luck.


At this point I'm out of ideas. Before I spend an hour switching back to the previous PSU, does anyone have any suggestions? Have I missed a plug somewhere?



Extra Background: I recently upgraded my graphics card from an old 7800 to a GTX260. Though everything started up, I ran into a lot of glitches & driver restarts. Eventually I underclocked the card to about 2/3rds of factory, and it began working fine. I didn't think heat was an issue, but my previous 600W PSU was somewhat old, so I figured it might be power. Hence my purchase of the HX850.

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Heh, stupid mistake after all. I'm embarrassed to post this, but maybe someone else will do the same thing at some point. While splitting the 8-pin 12V into 2x 4-pin (my MB doesn't have ESA), I got the directions confused, and plugged it in backwards. I just looked up the pin diagram for that plug, and it looks like this:





Really poor design on the part of ATX, in my opinion; 2 pins are square and 2 rounded, but they're on the diagonals instead of horizontal/vertical. If nothing else, they should have used this:





With the current design, it is possible to plug it in backwards, as I did. So no worries with the Corsair PSU (very well-designed from what I've seen so far). I just need to finish hooking things up again and hope my MB was smart enough not to let itself get fried by that mistake...

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