Computer starts then randomsly shuts down

[glenn469]

Hello,
my homebuild computer starts, then sometimes will boot (stay on) and other times turn off 1 second later, othertimes 30sec, completly random, it seems that it will shutdown like instantly, regardless of having a os, hdd's, dvd drives etc, just the basic mobo, cpu, psu and ram it seems to still fail. i have tryed resetting the bios, no change, removing the battery and still has the error. i dont have any spare parts to test as i gave them to friends. im using a giagabyte ga-x58-ud3r mobo, i7 950, 820w psu, gts 250 gpu. (yes its old) but can someone suggest to me what the problem could be?
thanks

 

[amuffin]

Your powersupply is not connected properly or is failing.

 

[glenn469]

psu is connected properly, but it could be faulty.

 

[glenn469]

tested powersupply in another computer, no problems. im guessing that the problem is in the motherboard, or cpu.

 

[ngrego]

Could even be your OS.
How long have you been running on your current install?

 

[glenn469]

its got no os anymore, problem occurs, regardless of having any drive, ive taken all the ram out, i seems to stay powered on, no image on screen though, but ive found some oud ram cards which im about to test

 

[Proximon]

Is the processor overheating?

 

[glenn469]

processor is fine in terms of temp, ive spoken to some other people and they have told me that i could be that there is too much power, or a faulty cpu. i removed all the ram, and inserted and tryed to boot each time after adding 1 card, it worked each time, im not sure why though cause ive tryed doing that many times b4 but problem still occured, it seems to be unstable and temermental

 

[jsc]

Your system will not POST without RAM. What kind of BIOS beeps did you get when you tested without RAM? Do you have a case speaker installed?

What brand and model is your PSU? I searched through newegg and did not find any 820 watt PSU's.

I'd try another PSU first.