Desktop PC Will Randomly "Turn Off" But Never Does

[Desisuperman]

let me explain..

1. I started noticing that my desktop was randomly shutting down
2. I turned off a feature within Windows that would prevent it from shutting down
3. Since then I have noticed the following
A. My pc will all of a sudden go quiet as if it was shutting down and then it powers back up as if it's been rebooted
B. It never does shut down or reboot but the hardware seems to be going through the process. ie. lights and fans shut off
4. I have since swapped out my power supply to no avail so it's definitely not that

Any other suggestions? I'm beginning to think my motherboard is failing. I have already lost a HDD due to this issue

Thanks in advance for the help and suggestions

 

[fralexandr]

Roughly how old is the computer?
Is it built by a manufacturer or is it a custom build?
What brand/model power supplies have you tried?
How old is the electrical at the property? Is the computer on a surge protector or a UPS/Uninterruptible Power Supply?

Could be the motherboard.

Which lights are going out? Are the lights from the case fans? Or the motherboard? Or the cases power led?
Do you have a fan controller or hub connected? Or do the fans connect directly to the motherboard?
Have you checked that the connections for the fans are secure?

A few pictures and/or a list of the computers specs and Windows version might help.

 

[Brainonska511]

Presumably, it is rebooting - I assume when you're back in Windows, it's like it had been shut down and turned back on (ie, programs don't all reopen).

In addition to the other questions asked:

What are the specs? Any recent hardware changes beyond the PSU?

Did this suddenly start happening? Is it intermittent or does it happen when you do certain things?

Do you have the latest BIOS installed? Do you have XMP enabled? You could also try checking the ram with memtest86.

 

[VirtualLarry]

I've heard of PCs spontaniously hibernating or sleeping. It tended to be a "bad motherboard".

 

[mindless1]

let me explain..

1. I started noticing that my desktop was randomly shutting down

What exactly is shutting down? What do you observe, specifically?

A. My pc will all of a sudden go quiet as if it was shutting down and then it powers back up as if it's been rebooted

What does go quiet mean? What do you see on the monitor? For example does it go dark, or if you wait a moment does it show a "no signal" message, or go to sleep, or ??

B. It never does shut down or reboot but the hardware seems to be going through the process. ie. lights and fans shut off

Do you mean it does either A. or B. at random, or is there some pattern to it?

I'm beginning to think my motherboard is failing. I have already lost a HDD due to this issue

What does "lost" a HDD due to this, mean? Sudden shutdown could certainly cause data corruption, but if it killed the HDD then you had to have a PSU problem.

Might be motherboard, I might try clearing CMOS and if it seems stable enough to do so, flashing a new bios if one is available.

Sometimes funny events like this can be caused by a flaky case power switch. That's easy to test by disconnecting it. What if you let it sit in a bios screen or boot to memtest86+ and leave it running to see if it does the same thing?

Not sure when I'll get back to this topic but the answers to the above might help or help someone else understand what is going on.