PC won't boot, fans spin, LED lights up, but CPU LED show red

[qiu_lijie]

Components:
CPU: Intel i7 4790k
Motherboard: ASUS Z97-A
PSU: Corsair CX750M

I built this PC a little over three and a half years ago, and it ran well till recently. Last week it won't wake from sleep/hibernation. After restarting it, there was no display output, but I notice by the sounds that I was able to log onto Windows. I thought I had resolved it though resetting the BIOS by removing the battery on the motherboard, and it ran fine for a few days.

However, all of a sudden it just won't boot now. When I press the power button, the fans and lights will come on. Like last time it had no display output, but unlike last time I don't think it boot into Windows, and the keyboard and mouse won't light up. The CPU_LED on the motherboard is red as well.

I notice that if I try to turn it on immediately after plugging PSU back into the wall outlet, the fans and lights will turn on for a brief moment, turn back off, then after a few seconds turn back on and stay on. But if it has been plugged in for a while, the fans and light would just stay on. I have disconnected all the non-essential components with only the motherboard, CPU, PSU, and one stick of RAM left, but the problem persisted.

At this point, I suspected either the PSU or the motherboard has failed, but can't seem to figure out which is the case. I'm at the end of my wit here, any help would be greatly appreciated!

Thanks,
Alex

 

[Kashimi]

Read this and follow the guide. If this doesn't work then we can go more advanced, but this solves the problem 99% of the time if the chip isn't fried :

http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

 

[qiu_lijie]

Read this and follow the guide. If this doesn't work then we can go more advanced, but this solves the problem 99% of the time if the chip isn't fried :

http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

Thanks for the quick reply. This PC did run fine for a few years, so I couldn't have screwed up that bad during the build. I did reconnect the motherboard and CPU pins. And I'm using the motherboard's HDMI output with my video card unplugged for the moment, which I'm not getting any.

 

[Kevin_138]

Random problems with an old PC?
Check for blown caps on the Mobo.
The capacitors can cause CPU failure and CPU failure like symptoms.

PSU testers are cheap, get one.

 

[qiu_lijie]

Random problems with an old PC?
Check for blown caps on the Mobo.
The capacitors can cause CPU failure and CPU failure like symptoms.

PSU testers are cheap, get one.

The capacitors are the cylindrical shape things on the Mobo, right? So I assume I will be checking for irregular bulging or deformations. Last time I check that there was no such deformation, but I will have a look over again after work today.

I'm 90% sure the PSU isn't the problem here now. I actually went out and got another PSU, and my PC still won't boot with it.

 

[Kevin_138]

Random problems with an old PC?
Check for blown caps on the Mobo.
The capacitors can cause CPU failure and CPU failure like symptoms.

PSU testers are cheap, get one.

The capacitors are the cylindrical shape things on the Mobo, right? So I assume I will be checking for irregular bulging or deformations. Last time I check that there was no such deformation, but I will have a look over again after work today.

I'm 90% sure the PSU isn't the problem here now. I actually went out and got another PSU, and my PC still won't boot with it.

 

[Kevin_138]

Random problems with an old PC?
Check for blown caps on the Mobo.
The capacitors can cause CPU failure and CPU failure like symptoms.

PSU testers are cheap, get one.

The capacitors are the cylindrical shape things on the Mobo, right? So I assume I will be checking for irregular bulging or deformations. Last time I check that there was no such deformation, but I will have a look over again after work today.

I'm 90% sure the PSU isn't the problem here now. I actually went out and got another PSU, and my PC still won't boot with it.

https://www.youtube.com/watch?v=oDGjWOabJ2E

They are the cylinder looking things.
They tend to bulge at the top and leak the electrolight out 🙁
This can get so bad, that I have seen a ram stick destroyed by the leaking electrolyte landing on it!!
Unfortunately they can also bulge at the bottom where it can't be seen .....

This is why I only buy boards with solid core caps.
edit
Just looked up ASUS Z97-A and to quote "ASUS High-Quality 5K-Hour Solid Capacitors - 2.5x long lifespan with excellent durability".

So probably not caps then................

I would take it all apart and reassemble it, surprising what that fixes.
Build it up bit by bit out of the case (poss shorts on stand offs etc)
Board , CPU and power, see if you get mem error beeps. if that gives mem errors then add the Mem.
If not (and a psu makes no diff) , guess board or CPU, but physically check both for signs of damage.
You get the idea...

 

[qiu_lijie]

Random problems with an old PC?
Check for blown caps on the Mobo.
The capacitors can cause CPU failure and CPU failure like symptoms.

PSU testers are cheap, get one.

The capacitors are the cylindrical shape things on the Mobo, right? So I assume I will be checking for irregular bulging or deformations. Last time I check that there was no such deformation, but I will have a look over again after work today.

I'm 90% sure the PSU isn't the problem here now. I actually went out and got another PSU, and my PC still won't boot with it.

Thanks for the advice, Kevin. I will give it a shot then.