New build+recycled bits; PSU problems?

[Mhorn2000]

Hey there, I've given it my best shot and now I'm turning to here for my first time for help.
Its a new build with some recycled materials being the RAM, harddrive (with a clean install), 800Watt PSU, and video card.

Current status of computer: turns on half a second, then turns off a few times. It has not powered on since.

Important note: It worked last night perfectly, it ran a high end game just fine. It booted up this morning, but when I tried to fix an audio jack on the front of the case it stopped working (aka, I turned it off, opened the front panel and it never powered on the same after). The parts DO work together when everything is working.

So my main concerns are that the PSU has stopped working or the power button on the front of the case has stopped working, OR the motherboard is toast(?)

What I've Done:
1. checked ALL power supply attachments. **The main power supply to the motherboard is missing what looks like a grounding pin** Looking at the plug I stick into the motherboard they all have copper bits except for that one slot.
2. I've changed power cords on the back.
3. I followed the stickied troubleshooting guide to the point where they have a multimeter. Everything is in order.

Quick edit: So if I flipped the switch on the power supply off for a few seconds, and then turn it back on and then power the front. It'll again turn on for a few brief seconds. Don't know if that means anything.

 

[inzone]

I would make sure that the front panel connectors are all pluged in all the wayand that none of them have been pulled out , the power and reset connectors and the usb ones as well since you were working at the bottom of the board and it would be easy for one of those little connectors to be pulled out.
The missing wire on the MB power connector is normal and you can test the power supply by doing the paper clip test which is taking the end of the MB power connector ( the end that plugs into the MB) and inserting a paper clip into the green wire hole and the adjoining black wire hole , you do have to spread open the paper clip so that you have the two ends available to put into the hols. If you Google "paper clip test" you can get the instructions online.

 

[Mhorn2000]

Inzone thank you for your input, but I've actually solved the problem. I tried a third power cable on the back and it now works (I try not to question the madness this has become).

I'm at another problem now. The computer doesn't seem to boot up the hard drive where the OS is installed. I can still get to the bios and what not with the Mobo though, but its asking for the boot disc and such if I don't prompt it.

actually it isn't detecting the harddrive at all. I'll update as this goes, checking wires.

 

[vertical777]

1. checked ALL power supply attachments. **The main power supply to the motherboard is missing what looks like a grounding pin** Looking at the plug I stick into the motherboard they all have copper bits except for that one slot.

that's normal

here are some things to try:
1 check for any shorts on or near the audio jack wire, probably inside your case.
2 check the front panel headers, as the guy above me stated
3 re-seat your ram and make sure they are put in snugly
*4 check for bent pins on the motherboard (if youre on intel), on the processor (on AMD)
*5 do not put your cooler on too tight if possible

*I had the same problem once (the machine would turn on for 2 seconds then turn off) those 2 were the 2 problems I found, apparently when you put the cooler on too tight the motherboard contacts get screwed over.

edit: whoops problem already solved, good for you

 

[Mhorn2000]

double update; Ugh, I may be working with some super loose wires, but things are up and running again.

I honestly, don't know what the problem was now. I'll admit I'm a COMPLETE newbie at this.

 

[inzone]

When ever you are working inside the case on any part of the computer you have o be aware of the wires and you can easily knock a connector out of place or loosen a connection so be aware of where your working and check the srrounding wireing before exiting the case to make sure that they are all tight.