Strange Issue with new computer

[rauchster]

Had just rebuilt a new computer with the following parts:
AMD Phenom II X4 940 CPU
ASUS M4A79-Deluxe Mobo
OCZ Reaper-HPC 2x2Gb DDR2 800 RAM
Xigmatek 750W Modular Power Supply
and combined them with parts from an old system build.
MSI NX8800GT 512Mb Gfx Card
2x Seagate Barracuda 500Gb HDD
1x WD Raptor 36Gb HDD (Sytrin Cooler)
Zalman 9700CNPS
LG DVD-RW Drive w/ Lightscribe
Cold Cathode Light system
Sunbeam Transformer Case

Build worked fine for about 72 hours, when this happened.

Had turned off the computer for the night.
Went to turn it on again the next morning.
All internal lights come on, and fans spin up normally, with no hesistation. But, there is no video output, nor is my USB Mouse/keyboard/headphones receiving any power at all.

The following has been done, with no results.
Took out each stick of RAM, and tried solo sticks in differing slots.
Disconnected all extraneous hardware except for motherboard/CPU/1 stick RAM/Gfx card/PSU.
Disconnected Gfx Card after that.
Reset BIOS using onboard switch. (multiple times)
Unplugged and replugged all power/data connections(including on the PSU), no loose ones found.
Disconnected Front Panel, and used onboard Power switch.
Tested PSU, seemingly works fine (Paper Clip test between green wire and ground wire, plus stuck in another computer)
Tested Gfx Card, works fine in another computer.

Thoughts:
While it certainly is possible that it is the RAM (haven't had access to a computer with DDR2 memory slots, will later today) or CPU (no access to AM2+ socket type either, same with later), I'm assuming that it is the motherboard.

Does this sound right to others?

The only thing that doesn't fit with the motherboard theory, is that it is responsive to the onboard switches (Cool 'N Quiet was re-enabled after a reset, I had disabled it / Power switch works fine) and all lights come on, even on mobo.

But I don't see why a bad CPU would prevent power from going out the USB ports to a mouse (green lights around outside of Razer mouose do not light up, ever. Works just fine on other computer. Same with lights on on Ideazon keyboard, and Logitech Headset)

Same with RAM. Should have no effect on USB hubs.

Recommendations????
I plan on taking this other AM2+ compatible computer, and swapping the CPU first. Then swap in each stick of RAM. Finally the entire assembly.

And then do it in reverse, by putting known working components in my bad build.

 

[Proximon]

Sure, it could be the motherboard.

I want to point out that the Xigmatek 850W failed completely, twice, over at Hardocp so it (your 750W) might not be the best choice. They do a good job over there testing PSUs. If the PSU was at fault and took out the motherboard, you might be heading for trouble by putting it in another system. I see no quality reviews for the 750W.

 

[rauchster]

Sure, it could be the motherboard.

I want to point out that the Xigmatek 850W failed completely, twice, over at Hardocp so it (your 750W) might not be the best choice. They do a good job over there testing PSUs. If the PSU was at fault and took out the motherboard, you might be heading for trouble by putting it in another system. I see no quality reviews for the 750W.

While I don't doubt that there have been bad reviews for certain power supplies, just because a single one got a bad review doesn't mean there isn't good qualities about a completely different model.
Just because one model from a car maker isn't that good, doesn't mean they are all bad.

I tested the PSU already anyways, since I had the abilities to do so.

Works fine in another system, and is pulling the appropriate amount of wattage. Volt meters read fine too. Nothing is ever lacking power when the source is directly through the PSU.

The only issue is any device plugged into the mobo isn't getting power.

 

[Proximon]

I should have explained myself a bit more clearly, sorry.

I'm not saying "all Xigmatek PSUs are bad." Indeed their 500W unit is probably good.

I'm saying that, in the world of PSUs, 750W and 850W models are often built on the same design, and come from the same OEM. I'm also pointing out that the two units they tested both failed in ways that could potentially damage a motherboard without necessarily giving any clue to how they were failing.

I'm agreeing that your motherboard probably failed, and suggesting that there COULD be a separate cause for that failure. It's a valid concern that you should be aware of when trying to troubleshoot and correct your issues.

 

[rauchster]

Understood.

Problem is resolved now.

Turns out that I overvolted the CPU while overclocking, and forget to swap out a jumper setting to allow for over 1.5VCore.
Put in a different chip (AMD Athlon), reset back to factory defaults, and put back in the 940, and it worked fine.