Computer turns on and immediately off

[luneki]

So my computer started failing yesterday.
It tries to turn on, the fans spin, the lights go on and one second later it turns off. After that it doesn't try to turn on unless I reconnect it.
Sometimes it will turn on, everything seemingly fine, log on windows, everything fine and suddenly it turns off and the process begins again.

What could the problem be?
Already tried plugging it into another surge protector, and directly to the wall outlet (and to another outlet to rule out it was the outlet failing) and it's still the same.
Could it be the PSU? Is it completely dead or just some sort of short that can be fixed?

 

[smorizio]

if it the power supply some time by removing the gpu it post as there less load on it. what brand is the power supply and it wattage??

 

[tsnor]

One (or more) of your parts are failing or is no longer making good electrical contact (e.g. corrosion in slot). Could be power supply, but it could just as easily be memory, or disk or video or MB or ... anything electrical.

There are a few other things that could do this. CPU fan not spinning. CPU Overheat. YOu can rule out the cpu fan by watching it spin up on boot. Either it will spin briskly as normal, or it will be stopped or spinning slowly and irregularly. Likewise you can rule out CPU overhead by opening case and blowing a fan into the case towards the CPU cooler. (Not a bad time to blow out the dust)

Standard debugging is to remove parts until the system does not fail, then add parts back in until it starts failing again, then swap that last part out for a known good one. You do the extra step of adding the parts back in because sometimes re-seating a failing part is all that is needed to get it good again.

Your situation is more complex since your fail is intermittent -- sometimes it works. So when you pull a part and the problem does not happen you are not sure if the part you pulled was really the part.

Try the guidance in the "no boot, no post" sticky. It's geared for a new PC but you can adapt it to what you are trying to debug.

It is very expensive to start guessing which part is failing, you can end up almost buying a complete new PC one part at a time. The only three parts you every need to guess on are the MB, CPU and PSU, and it's never the CPU. The remaining parts you can rule out by seeing changes in behavior when you remove the part vs. when it is in the PC. This is discussed in the "no boot" sticky and the posts linked from the sticky.

Good luck.

 

[luneki]

if it the power supply some time by removing the gpu it post as there less load on it. what brand is the power supply and it wattage??

There's no gpu, using i5 6500 igpu. PSU is Corsair CX450M, 450w.

 

[smorizio]

if the power supply under warrnaty ask for a cross ship if they do it. if you have a friend that have a digital volt meter. open the case and put the black ground lead on any black wire. print out from googlt atx spec and power supply pin outs. use the pin out to mesure the voltage on the 24 pin atx power cable. see that the 3.3 5v and 12v line are holding. if not send the unit back and retest with a known good power supply.