Computer Not Powering Off Completely

[jslowik]

Hey guys, I think I know where the problem is, but I think in my desire to have it not be the motherboard that's toast I'm going to toss the question out to you guys for a second opinion.

 

I've got an old computer (LGA 775) that I built many years ago, and gifted to a family member some time ago. It was kind of flaky at the time, but seemed moderately stable save for one issue. When you shut the system down, it appears to turn the system off, however all the fans in the computer continue to spin (and actually spin up to full speed in the case of the GPU at least). I believe the hard drive and other components are actually powered off, but I'll be honest I haven't really verified that.

 

To answer the thermal response I'm sure I will invariably get, checking temps reveal nothing is higher than would be expected for that processor at idle, and I've also swapped graphics cards to an older and slightly defective (but still essentially functional) card. No change.

 

At this point I'm nearly certain that it's the motherboard which would be exceedingly frustrating due to it running initially an OEM Windows 7 license, and more recently upgrading to 10. Basically I'm hoping someone might have a shot in the dark idea that ends up being the silver bullet on this one so I don't have to replace every single thing. I will mention I have not looked at the power supply as a possible problem as it's never exhibited any of the more common symptoms of being on the way out. If I'm wrong and this actually is one please slap me with a trout or something.

 

Thanks for any ideas you might come up with or at the very least thanks for confirming my theory.