New case, Power problems

[freedonutss]

Hi, I just but a new aspire case in replace of my HP Media Center m700 case. I hooked all the connections up correctly, tried a few different power supplies. Still no good. When I turn the computer on the fans spin and the computer boots up but 2 seconds later it turns off. Anyone have an explanation for this?
Intel 2.8ghz HT Northwood Processor
1.5 Gb of Ram
Aspire 520w ATX Power Supply
ASUS Atx Motherboard
ATI Radeon 9200 128mb 8x AGP Video Card
Aspire X-Nightmare Case

Need some help.

 

[freedonutss]

Also, I left everything the same. Just basically transferred everything from the hp to the new case.

 

[CrazeD]

Did you make sure the metal spacers in the chassis (to hold the motherboard down) are placed correctly? If they arent, they can short the motherboard out and that will happen. It should be fine if you move it though.

 

[freedonutss]

Placed correctly? I mean theres only one place you can put them. Do you mean if I screwed them down too tight?

 

[junglemike]

Placed correctly? I mean theres only one place you can put them. Do you mean if I screwed them down too tight?

It might be, after following CrazeD advice check everything - maybe you dropped something metalic that shortens the board, or cables plugged incorrectly, etc.
PSU shuts off when it's either overloaded or there is short circuit on either of it's power lines (3.3v, 5v, 12v)

 

[freedonutss]

I might of found a problem. The power supply that came with my computer only has 19 pins inside of the 20 pin connector. My new power supply has 20 pins inside the 20 pin connector. Would that 1 pin be overloading the motherboard? Its also in a weird position. The stock power supply 20 pin connector is missing its top row, 3rd pin from the right connector. On my new power supply which one should I remove?

 

[freedonutss]

Also, How would I remove the 1 pin wire from the 20 pin connector?

 

[junglemike]

Don't remove anything! You will kill your board.
Listen, the pins missing might be notheing wrong.
In this cable there are many parallel wired carrying same line current that are doubled or trippled for redundancy for redundancy.
If it's standard 20 pin power ATX connector, it's scheme should look like this:
http://pinouts.ru/Power/atxpower_pinout.shtml

For example, there are 4 wires with +5v line (RED). These wires are pretty thick, even a single one of them can carry some 100amps, so lf one of red wires is missing - it's not big deal.
Now If you really want to check your PSU - just take a voltmeter, and test all psu lines (3.3v, 5v, 12v...) and make sure they are deviated not more than 5% from the values in the link above.

 

[freedonutss]

Hmm... I know the power supply isnt bad. Ive tried many differnt ones but still the same problem.

 

[freedonutss]

What it seems like its doing is, when I hit the switch the power comes on then cuts right off. After that the power supply goes dead for about 10 seconds. I tried this with 2 different psu just now.