Jan 22, 2018 - Does your computer keep turning off unexpectedly? So try to clean the computer especially the fans and the filter. Check if fans.
with nothing attached. IE: no addon cards no HD no CD/DVD. Have you tried another PSU (Power Supply Unit) as something maybe triggering the over voltage detection.
back of power supply a little red switch make sure its set to 115
First thing to try is loosening the Screws that hold the Motherboard to the Case. They will only need a full turn. Reconnect the Power and turn it on. If it powers up shut it down and retighten the screws. They only need to be firm.
Make sure that there are no loose screws or other components inside the case. These can cause shorts and other serious problems with the PC.
Also check the power outlet that you are connected to by plugging in something else and turning it on.
A faulty (PSU) Power Supply Unit can also cause it. Fluctuating power or an underpowered PSU is not good for the Motherboard. You should be running 500-600 Watts. Try another one if available or replace it.
If it's none of the above try this Bench Test.
Carefully remove everything from the Motherboard. Remove the Motherboard and put it on an anti-static mat on a bench. Check the mounting stands and make sure that they line up with the holes on the Motherboard and they are all of the same height, so they are not shorting out the Motheboard. Remove the Power Supply if it is a known working one to test with. Remove the Heatsink and give it a good clean. Remove the CPU and reseat it. Reinstall the Heatsink remembering to use CPU grease. Reseat the RAM and test with one stick at a time. Connect a hard drive and the Video Card. Connect the Power supply to the Motherboard. You can use a flat blade Screwdriver to short the Power pins on the Motherboard if you haven't got a spare switch. Connect the Monitor and turn it on and see what happens. If it stars up add one Device at a time to test it.
Troubleshooting Flowchart
http://www.fixingmycomputer.com/flowcharts/boot-up-flowchart.html
you have a 450W PSU and your running a quad core and a HD 4850 gfx card...
I have a 4830 gfx card and the min power requirements are a 450W PSU
I also have a high power dual core CPU (but uses a lot less power than your quad core)
I have a 650W PSU
if you built this system yourself get a new more powerful PSU... If somebody else built it for you go smack them in the face for insulting your power needs.
you should have at least a 500-550W psu
I was researching the min requirements for HD 4850 graphic cards, and the min is 450 watts. Which you are meeting. But if you are constantly drawing the MAX that the PS is designed to handle, then you will burn it out pretty quick.
Snuffy is right min. PSU you should go with is 500-550... but if you can find a PSU that is 650 W for the same price as the 550Watt jump for the 650, it will be better for future upgrades...
I will get another more powerful psu. thanks all. i will repost if the new psu doesnt fix the problem
As suggested, checking the voltages should give you the clue that the power supply has failed. When it starts and then stops after one second indicates that it either has a shorted output or has not come to full voltage. A miltimeter should confirm whether it's the 12 volt or five volt supply that has failed. Since you've replaced the MOBO and it didn't cure the fault, the power supply is the only other solution.
What would be a good power supply to get?
in terms of wattage. how much would be enough for my pc.
600w? more? less?
thanks in advance
Start from scratch, fill in ALL the details that you can:
http://www.antec.outervision.com/
Recheck everything you've entered as detail (just in case) then move up to the next available PSU.
550-650W should be OK for your setup.
eXample:
http://www.antec.com/Believe_it/product.php?id=MTc1OQ