PC powers on but does nothing else, no response from screen, no power to USB devices and cannot be force shut down

[pussaydestroyah]

First off, I'm very sorry for the wall of the text and I hope I've provided the problem and any relevant information to the best of my ability. I will be damn grateful for some insight into this.

Okay, so a few days ago I returned back to my house at University after going home for the holidays and had bought my PC home with me and it was working fine. Upon bringing it back I found that it wasn't powering on properly in which I eventually discovered to have been caused by one of the standoff screws coming loose and the motherboard touching the case. After fixing this the computer did start working and started up properly but only for so long before it completely froze and I had to force shut down.

After this things only seemed to get worse, after trying to restart I was able to log on and the computer would run fine for around a minute for automatically restarting, the power didn't switch off or anything it just returned to the startup BIOS screen and booted up as normal. I logged back on only for the same error to occur. This happened a few times so I tried booting up in safe mode, same thing happened. After this I tried to Launch last known good configuration and I had tried up startup repair, but nothing. Each time the screen would go black, the computer would stay on and I was unable to force shutdown using the power button as it seemed even that had become unresponsive and so I had to flick the switch at the back. Now the computer when I turn merely powers on, the fans begin working, I can hear the normal sounds, there are no beeps but the USB devices attached do not have any power going to them, the screen has no signal going to it and in order to turn the PC off I have to flick the switch at the back.

I recently whilst at home for the holidays reapplied thermal paste after overheating problems and it was running smoothly and better than ever until I had to move it up back up the country. Obviously the motherboard had been jogged but I had fixed that. I checked the RAM to see if it was seated correctly, it was. I had checked all the wires were plugged in firmly to the motherboard and to the PSU. Two things I should mention, both being stupid mistakes was that one, I had used the wrong power cable on the PSU when I first put everything together (is there a chance that this being the wrong voltage may have blown or damaged the PSU? I corrected this mistake immediately and like I said, I was able to power up for a while and log in) my second mistake was that when trying to take a cable out of what I hadn't realised was a loose motherboard I accidentally pulled too hard and heard something on the motherboard make a small snap but I'm sure that was just the screw as it caused it to fall out.

I currently have no way of accessing my PC and am not sure what to do. My specs and hardware are:

AMD A10-5800K 3.8GHz Quad-Core
ASRock FM2A75M-DGS Micro ATX FM2
Corsair XMS3 8GB (2 x 4GB) DDR3-1600
Western Digital Caviar Blue 500GB 3.5" 7200RPM
Silverstone RL01B-USB 3.0 (Black) ATX Mid Tower
Corsair 500W ATX12V
LG GH24NS90 DVD/CD Writer

I'm not the most experience PC builder, this is my first build, it's been healthy for 2 years so im assuming that I've damaged it somehow but I have been very careful. If you're going to tell me to do tests I would appreciate it if you could maybe tell me a little bit more about how I can do these tests as I've seen them mentioned on other posts and had no idea what you guys are on about.

Thanks in advance

 

[Entomber]

I'm not sure what to think about the small snap that you heard when you were forcing something out of your motherboard, it sounds like you may have damaged it quite seriously.

 

[herrwizo]

From the symptoms, I would say that either the mobo (more likely) or the PSU (less likely) are starting to fail or already partly failed, but it's maybe too early to jump with the conclusions so do the following.

First, unplug the PSU from the wall. Then remove the BIOS battery from the mobo, wait a few minutes and put it back. Remove both RAM sticks, put back only one of them. Try again. If it fails, try only with another RAM stick. And if that fails... well...

You will have to test every single component in a different rig. RAM, graphics card, hard drives and add-on cards should all be tested.

If they all work, get a different PSU just for test (or borrow one) and try again with your own rig.

If the symptoms are still here, I'd say this mobo is done for.

 

[herrwizo]

Oh, and as a last measure... (this is a desperate one, but I have seen it work a few times): assemble the rig outside of the case. Sometimes there are grounding isssues with certain cases. This has to be determined.