Is this a mobo that has been working and then all of a sudden stopped working? Or is this a recent build and you're troubleshooting why it won't boot?
If it's a recent build, I'd check the mobo manual and confirm you have the power connectors slotted in the right places. I.E. Power LED, HDD LED, Reset LED ... etc. Perhaps some of them are incorrectly placed.
And you've confirmed the capacitors are not blown?