Strange Bootup/Power issues

[TheUnluckyOne]

So I finally got around to throwing together some parts that I had or was given for a computer, but I am having a lot of bootup or power issues that I don't know what to make of. The system specs are as follows:

 

CPU: Intel I7 870

Motherboard: Zotac H55-ITX-C-E

RAM: 8GB 1600 Corsair 

PSU: Seasonic S12G-550W

Graphics: EVGA GeForce GTX 680

SSD: Crucial M500 120GB

Case: SG08

OS: Windows 8.1

 

Yes I know the parts are...well....old, but it works (sometimes, we'll get to that) and it's a huge improvement over my laptop. I'm not sure what the BIOS version is off the top of my head (on campus right now), but I'm pretty sure it's not the most recent version. I didn't update it because right now I'm not confident that the computer won't turn off by itself, which if it does in the middle of a BIOS update can cause problems needless to say.

 

The problem that I'm having is that...let me just describe it. When I first put everything together, the thing wouldn't boot at all, but some of the motherboard's LED lights would turn on, signifying that power was being delivered. At first I thought it was the power button on my case that was bad, but that turned out to be not true. So I checked the connectors and everything seemed to be properly seated, but I found that slightly pushing up on the video card would cause the comp to start. Odd right? But the power button still wouldn't work. So I thought maybe something made its way under the motherboard and was causing problems or perhaps something wasn't seated properly, so I took everything apart, and there was definitely nothing there. So I put everything back together and everything seemed to work properly, but when I just tried to gently nudge the computer to a better location on my desk, it turned off by itself, and once again nothing seemed to work, except the motherboard LEDs. Then I found that pushing the 4 pin power seemed to cause all the fans to spin, and after jiggling with the power plug in the back of the comp a bit, it would turn on by itself and after that everything seemed to work properly. I was able to install windows, get everything set up, etc. But wait! There's more! I plugged an external hard drive into the USB3, and the entire computer turns off and refuses to do anything, in fact anything plugged into the USB3 stops the computer from doing anything. I found that sometimes if I touch the USB3 plug to the connector on the back of the mobo (not plugging them in), all the fans will spin. Apparently sometimes putting a bit of pressure on or jiggling some random bits here and there can cause the computer to spin the fans or turn on the comp...which is weird. Also I find that just the simple act of plugging in the power could get the computer to start. 

 

Also the BIOS seems to reset every time it goes through one of these episodes. Here is a link to the image of the screen if it helps: http://imgur.com/pr9FIGr

 

All of that being said, the computer DOES work. I was able to install windows. I was able to game on it last night with no issues. As far as I can tell, things are stable after I "fix" it after one of those episodes. The problem is if I try to move it or use the USB3, then it seems like it could stop working, and then I'd have to do that song and dance again to get it to work again. 

 

Does anybody have any idea what could be wrong? At first I thought maybe 550W wasn't enough and was causing the random instability despite my research seeming to indicate that it was no problem, but I'm not seeing instability when the computer actually works and is under load, and it doesn't make sense with the other symptoms. Maybe there is something wrong with the PSU itself? Seems unlikely to me also because aside from the weird problem listed, the computer seems to work properly even when under load. Maybe the connectors aren't seated properly? Possibly, but I've already re-seated everything more than twice, to say the least, and I would like to think that I am at least competent enough to do that. The power button itself is bad in some way? It works just fine after I "fix" the comp. Maybe the power cable thing that comes with the SG08 that connects the PSU to the back of the comp is bad in some way? Possibly. It may explain why simply plugging the comp in can get it to start, but it doesn't explain how messing with other random connectors/things on the comp can get things started. The motherboard is bad in some way? This seems to be the most likely scenario in my mind, as it could explain why the bios re-sets after one of these incidents, why I have issues with the USB3, and how messing with random stuff connected to it could get things started, but at the same time, it doesn't feel like a great explanation either because the computer works fine it seems after "fixing" it after it goes through one of the mentioned episodes, power buttons and everything.

 

I spent all last night and part of this morning trying to figure this out and I've gotten nowhere. So basically my solution has been to don't move the damn thing, don't use more USB devices, and don't touch the power connector, but this can't be a solution in the long term. I'd appreciate it if anybody has any thoughts that can help me fix this issue because I'm seriously at a loss.

 

Thanks.

[Hodge1997]

see if there are any extra standoffs in the motherboard tray, and see if putting the power supply in a different computer to completely rule that out.