New system build won't POST

[Chang10is]

I built a new computer today. Unfortunately, it won't POST. When I push the power switch, all the fans turn on (PSU fan, case fan, CPU cooling fan), but my monitor doesn't get a signal. My motherboard doesn't beep either. I hooked up a pair of headphones to the back audio out jack and still didn't hear any beeps.

Here's what I've tried:
- reconnecting the monitor
- reseating the RAM
- one stick of RAM at a time
- disconnecting hard drive, DVD, keyboard, mouse
- reseating the CPU
- different PSU
- resetting the CMOS via jumpers
- resetting CMOS via jumpers after taking out battery

None of the above changes anything. Computer also won't turn off unless I flip the PSU switch. Pushing/holding in the power switch on the case doesn't turn it off. Any ideas what's wrong?

Here's my setup:
- Gigabyte GA-MA785GM-US2H
- Phenom II X2 545 Callisto
- OCZ Reaper HPC 4GB (2 x 2GB) 240-Pin DDR2
- Thermaltake TR2 W0070RUC 430W

Other thoughts:
At first, I thought maybe my RAM was having compatibility problems with my mobo, but then I read in the comments for my RAM that it worked fine for somebody with a similar mobo (Gigabyte GA-MA790X-UD4P). Then I thought the fact that my mobo doesn't even beep when I hit the power means that the mobo was DOA. Or maybe that could also mean the CPU was DOA? The box that the CPU came in was slightly crunched in on the corners. The CPU looked fine when I inspected it, I'm guessing it got knocked around during shipping. Then there's the fact that the RAM was packed together in the same box as the power supply, and there was practically no cushioning between the two. That can't be good.

Any help figuring this out would be really appreciated!

 

[jackschmittusa]

Take the mb out of the case and try it. You may have a 5v short somewhere.

 

[Chang10is]

Originally posted by: jackschmittusa
Take the mb out of the case and try it. You may have a 5v short somewhere.

Sounds a little risky... is there something else I can try? Or maybe somebody already has a good idea what's broken and I can go ahead and RMA something.

 

[imported_Mills]

I had a similar problem and it was that I didn't have the 8pin motherboard connector properly connected. Something to check.

Mills

 

[Chang10is]

Good call, Mills. I just came back to write that I figured out what it was, and it turns out you had the same problem I did. The last computer I worked on didn't have a separate 8- or 4-pin connector, so I didn't know to look for it originally.

 

[Backdraft11]

I am having similar problems as you and have a Gigabyte board as well (GA-P35-DS3L Rev 2.0), except that this time I was trying to bring it out of standby and it suddenly would not startup. Tried a manual shutdown using the front power button but then it wouldn't even POST now. I've tried the things the OP has listed as well and it still won't.

I'm going to the local shop to pick up a mobo and perhaps PSU, as I see no solution to my current situation my current setup.