PC was fine last night, this morning I hear fans but nothing else (no display, beeps, etc)

[TylerJVezina]

Last night (and for several months) my PC was working just fine, but this morning I went to wake it up and nothing was responding, even holding the power button. It appears something went wrong overnight.

What happened:
I typically lock my computer before bed, letting the monitor go into sleep mode, and hit enter on my keyboard in the morning to wake it up. This morning, the power button light and the lights on my headphones were still on, but pressing enter did nothing, then holding the power button did nothing, so finally I flipped the PSU switch to shut it down.

Now, when I power on my PC, the PSU and CPU fans start running, and one of the activity lights on the front of the tower turn on, but the power button itself doesn't light up, keyboard doesn't light up, there are no beeps, and no display.

Tower history:
This was originally a pre-built store bought PC something like 8 years ago. I upgraded the RAM, GPU, and PSU not long after that, then the PSU died and was replaced again. A few months ago, we used a few parts in a 2nd PC and I got a new HDD, PSU, GPU, and CPU for it all at once. It's been running fine since then for all these months, and now something's apparently gone wrong overnight.

Specs:
I'm sorry, this is going to be rough - I normally run CPUID to remember what all my components are, so I'm running from memory and looking at the parts in the tower:
Mobo: AMD, no idea what model
CPU: An AM3 socket I got from a friend (mobo is AM2 socket, but the CPU is compatible)
RAM: 8GB DDR3
PSU: Corsair CX600W
GPU: GTX 650 Ti Boost
HDD: Western Digital 1TB

What I've tried:
1. Unplugging/turning off for a while (5-10 min), reconnecting and turning on.
2. Checking inside for any obvious issues (looks fine to me).
3. Running through this guide, checking connections, etc.
4. Unplugging the PSU-to-CPU 4-pin power connector (same problem whether or not it's connected)
5. Swapping out a different PSU, same problem.

Thoughts:
I'm not a PSU expert, so when setting up the most recent new parts (PSU, CPU, HDD) I was following all the guides I could and using another PC as reference - on the one hand, it's been running just fine for months, but on the other, maybe I missed something or something came loose? The guide I linked to earlier mentioned making sure the system speaker that beeps is plugged in, but I don't know where that is, so maybe I missed that when hooking everything up, which would explain the lack of beeps?

Secondly, I found this post with a seemingly similar issue, and his solution was that one of his PSU-to-Mobo connectors wasn't plugged in... I'm not sure that applies to me, as I only see 1 mobo plug, yet he had the same problem where the power/reset buttons on his PC weren't working either.

I'm at a loss (and fairly upset, I can't afford new parts right now if something died!) so I'd appreciate any help I can get! In addition to suggested actions, does anyone know what part(s) are likely the cause of these symptoms? Thanks!

Edit:
It occurs to me that my PC starts up (fans running) when the PSU is switched on and there's no way to shut it down since the power button doesn't work. Seems odd to me that the tower doesn't stay powered down ever, but turns back on immediately on getting power, as if recovering from a power outage...

Some photos for reference (with GPU removed): http://imgur.com/a/45ZzK

 

[Nerdy Nerd]

Sounds like the psu is not providing enough power. I would check the psu first, then check the power switch or another wards the button you press. If you went through that post, then I do not know what is wrong with your system though. Did you actually go through the entire post?

 

[TylerJVezina]

I did run through the whole post to the best of my ability, it's possible I misunderstood something.

I've taken some photos in case it helps (I removed the GPU to see better): http://imgur.com/a/45ZzK In the last photo (sorry, I don't know all the names for the parts) the big 24 pin plug that connects to the motherboard appears to have a piece of metal missing... not sure if that's normal or means anything.

I also tried unplugging the CPU power connector cable and turning on the PSU - same issues (no beeps or display) whether or not it's plugged in, so it seems that's related. Is it possible that specific cable from the PSU has stopped working?

Oh and, please be gentle if the photos reveal that I've done something utterly moronic. XD

 

[TylerJVezina]

Update: I just got ahold of another PSU, swapped it in, and still the same problem. 🙁

Does that mean it's the motherboard (specifically, the CPU power connector isn't taking power any more)?

 

[Nerdy Nerd]

If same problem with another psu, then that means you can rule out psu. Also, you mentioned trying without cpu cable plugged in, that you cant do as a computer needs 24 pin and cpu cable plugged in at minimum and that will not load an os. So that did not help you at all. The another psu test did help you, it ruled out your psu. You also mentioned a metal piece off or something? I looked at the photo and couldn't really tell. Did you mean the piece of the 24 pin on the motherboard or the psu? Anyways, if you went through everything on that site, I am not really for sure what it is. At this point, I would get a post card reader that goes on your pci slot on the motherboard. It will give you a code and based on that, you can look up the code in the booklet it comes with or just look it up on google. That will tell you what the problem is. You could also try another cpu and see if it is a cpu problem.

 

[TylerJVezina]

For the record, it *was* the motherboard that died. I got a replacement, PC is up and running again.