PC Will Not Boot

[Abluhwleh]

Hi all, bit of a weird one. Just before Christmas, pc shut off and would not boot back up. Power LED comes on and fans spin for less than a second, then dies again. Power switch then becomes unresponsive until I unplug it, leave it 30 seconds, then plug it back in, which gets me that less than a second of activity. Power supply tester from Amazon shows everything fine with that. Replaced processor and motherboard. Tried the usual moving around of RAM sticks. Removed graphics card and tried booting to integrated graphics.

Any suggestions greatly appreciated because I am out of ideas and can’t afford to just keep throwing new bits at it until it works.

 

[Bill_Bright]

PSU testers are great for verifying a PSU is bad - if, for example, it is missing a voltage. But they do not verify conclusively a supply is good. They don't provide a variety of realistic loads nor do they test for ripple or other anomalies that affect stability. You need to swap in a known good PSU and see what happens.

 

[Shrek]

Might want to try removing everything (hard-drive, graphics card, only one RAM stick) as a diagnostic to see if the power supply can limp along with low load.

But don't keep throwing new bits at it; can you borrow another power supply to try?

 

[Abluhwleh]

Sadly, neither I nor anyone I know has a spare power supply lying around. Have tried removing everything, even took the board out of the case in case it was weirdly shorting somewhere, with no change.

 

[Bill_Bright]

So you have tried two different CPUs and two different motherboards, inside and outside the case, graphics card and integrated graphics and it still does this? There is little left to try.

You said you moved your RAM around, have you tried running with just one stick of RAM?

Did you ensure your CPU and RAM are compatible with that specific motherboard? On the motherboard's webpage, there should be CPU and RAM QVLs (qualified vendors lists) of compatible CPUs and RAM. You should buy a listed CPU. There are too many RAM makers and models for board makers to test them all so you don't have to buy listed RAM but you should buy RAM with the same specs as listed RAM.

 

[Abluhwleh]

So you have tried two different CPUs and two different motherboards, inside and outside the case, graphics card and integrated graphics and it still does this? There is little left to try.

You said you moved your RAM around, have you tried running with just one stick of RAM?

Did you ensure your CPU and RAM are compatible with that specific motherboard? On the motherboard's webpage, there should be CPU and RAM QVLs (qualified vendors lists) of compatible CPUs and RAM. You should buy a listed CPU. There are too many RAM makers and models for board makers to test them all so you don't have to buy listed RAM but you should buy RAM with the same specs as listed RAM.

Had never heard of a QVL before now, checked and thankfully both CPU and RAM are on the list, so that was lucky. I have tried just one stick (both of them individually).

 

[Bill_Bright]

Had never heard of a QVL before now

Nearly every, if not all, motherboard makers maintains those lists for nearly every, if not all of their motherboards. So whenever building a new computer, or upgrading the RAM or CPU on a current computer, be sure to check them out.

As Shrek suggested above, disconnect your drives and try that - just in case one has some fault that is causing the system to shutdown. Without a drive, the system should still boot past POST (power on self test), then error out when it cannot find a bootable drive. But at that point it should keep running.

Beyond that, since you have tried everything except a different PSU, I don't know what else to suggest.