I have had my 790i Ultra SLi for a while. Love it. I don't feel the need to replace it with an i7 as with the OC I have it's lightning fast. 
 
Last week I went to power it on as normal. No dice. I had put a GTX580 in it, and then sold it and went back to my 280's, but it worked fine after the change. Just one day it decided not to power up any more.
 
The standby power light is on. When you hit power, the LED for MEM power lights up, but that's it. No beeps, no fans, nada. I even benched it with only the Mobo, PSU, and the CPU fan/liquid cooling pump. No dice.
 
I replaced the PSU. No dice. I reset the CMOS. No dice. 
It's not powering up the board at all. 
 
SO....any ideas?
What does EVGA charge to repair a motherboard these days? I mean I can't even find one of these used for a decent price. 

Try re-seating the battery, it might have a low charge. (or replacing)

What's the battery model for that? I'm at the office at the moment. I may go out at lunch and grab a new one. For $2.00 I'm willing to swap it out to see if that's the issue. 

No dice. 

You could try re-setting the power supply.
Unplug.
Then push power button for 10 seconds to discharge residual current. 
Wait 60 seconds then re attach power cord.

Check to see if any of the capacitors are leaking.  I had the same happen to my 780i board a few weeks ago and it had 2 blown capacitors.

Hello.
Seams i have similar problem.
i have used my PC for 2y now. And 2 weaks ago i went on a wecation. Now that i cam home i trayed to turn it ON, but nothing. I se there is a power to on board blue STBY LED. Nothing was changed and no 1 did anything to it. But for some reason, it just docent want to start up.
 
1. i trayed resetting my BIOS,
2.  switching the battery,
3. unplugging the power supply resetting BIOS again,
4. unplugging everything to peaces and getting them back together.
5. i have power regulator so im safe from electrical overcharge.
6. On board "power on batten" docent work.
7. ... help!!
 
 
EVGA 790i ultra SLI
2x  GeForce 260GTX
quad core intel 2.5Ghz CPU (OC to 3.0 GHz )
2x4GB viper 1800MHz RAM
650W extreme  chiftec power supply
 
And like i sed, every thing was working perfectly before i want of 2weak wecation, and now it just docent want to power up.

I have had my 790i Ultra SLi for a while. Love it. I don't feel the need to replace it with an i7 as with the OC I have it's lightning fast.  

Last week I went to power it on as normal. No dice. I had put a GTX580 in it, and then sold it and went back to my 280's, but it worked fine after the change. Just one day it decided not to power up any more. 

The standby power light is on. When you hit power, the LED for MEM power lights up, but that's it. No beeps, no fans, nada. I even benched it with only the Mobo, PSU, and the CPU fan/liquid cooling pump. No dice. 

I replaced the PSU. No dice. I reset the CMOS. No dice.  
It's not powering up the board at all.  

SO....any ideas? 
What does EVGA charge to repair a motherboard these days? I mean I can't even find one of these used for a decent price.  

 
I know this sounds crazy but I only say it from past experience. One time I Swapped video cards and I must of screwed it alittle tight because it was causing the motherboard to touch the bottom of the case in a weird way, I guess a little flexed if you will, and I was unable to power up. I though the mobo needed to be rma. I loosened up the card screw a little and loosened up a couple screws on the mobo and boom, got power and it turned on. I could actually hear a little bzzzz if Id push the  board hard on the case bottom and the led's would turn off, let go, and it would turn back on... LOL. Just a suggestion, loosen it up or take the board out of the case and try to power on