Question PC not POSTing - no beeps - is it the CPU?

[Quitchy]

My PC has stopped POSTing and no beeps are being issued.

I have tried a known-good PSU from another machine, which didn't fix it. I also tried replacing the motherboard with a new one, identical make and model, also without success. Am I correct in thinking that the only other other piece of hardware that could cause these symptoms is a faulty CPU? Due to the cost of replacing it I want to make sure I'm on the right lines before proceeding.

 

[rgd1101]

full system spec? include brand and model of the psu

 

[Quitchy]

AMD Ryzen 7 3800X
16GB DDR4 (2x8)
Nvidia RTX 2060
Asus PRIME X570-P
Corsair VS650 PSU

The replacement test PSU was a Corsair AX850. Motherboard replacement was new and like-for-like.

I should add that the PC used to boot up fine, it recently started to crash and then one day would not POST at all. PC switches on, fans go to 100% and stay there, no beeps, display doesn't initialise. The build is ~2.5 years old.

Motherboard has a light to indicate power which looks to be under the motherboard fan/heatsink. Can't see any indication that it has other status lights present.

 

[MeO123]

Try to test without GPU, and with only one stick of RAM on motherboard.
Are you 100% sure all your connectors are tight and good?

 

[Quitchy]

Try to test without GPU, and with only one stick of RAM on motherboard.
Are you 100% sure all your connectors are tight and good?

Without GPU and without RAM doesn't appear to change anything. Without RAM I'd definitely expect beeps. Also tried with each stick individually for no change. Finally, tried a different GPU (GeForce GTX 980 Ti) and on a different (known good) HDMI cable and monitor. The only noticeable change here is that the CPU and chassis fans ran a little slower, but the replacement GPU required double the power connections and had three fans instead of two, so I put it down to this, otherwise no changes were noted.

Connectors have been redone due to motherboard change, and everything looks good. All expected power indicators are on.

At this point if it's not the CPU I have no idea what it could be, unless the case has started emitting some magic anti-boot field.

 

[CrimsonJukebox]

Without GPU and without RAM doesn't appear to change anything. Without RAM I'd definitely expect beeps. Also tried with each stick individually for no change. Finally, tried a different GPU (GeForce GTX 980 Ti) and on a different (known good) HDMI cable and monitor. The only noticeable change here is that the CPU and chassis fans ran a little slower, but the replacement GPU required double the power connections and had three fans instead of two, so I put it down to this, otherwise no changes were noted.

Connectors have been redone due to motherboard change, and everything looks good. All expected power indicators are on.

At this point if it's not the CPU I have no idea what it could be, unless the case has started emitting some magic anti-boot field.

Hey, I'm running into similar issues with my desktop. Tried all the troubleshooting steps you mentioned as well. Even tried with different motherboard and RAM sticks to end up with the same results = no POST.

I tried booting it without the CPU and had the same result. I thought the BIOS would show up when booting without the CPU, but I guess it's not the case since both MOBOs have the same behaviour. I'm trying to discard other things but it seems like it may be the CPU. I'll update whenever, if, I manage to solve it.

 

[Quitchy]

Ultimately this turned out to be a GPU issue. No beeps were occurring because nothing was attached to the speaker point on the motherboard.

Initially GPU had been ruled out due to a replacement being used. But this GPU proved to be a poor test as it was a 240W draw versus the 170W draw of the one it was replacing, which provided a misdiagnosis.

 

[CrimsonJukebox]

Thanks for the update.
What solved my issue in case it helps anyone else in the future: It was the CPU. Got a replacement CPU and it booted fine.

I had a couple of colleagues who were pretty sure that I should be able to see the BIOS of the MOBO regardless of a faulty CPU or if I had any installed at all, alas it was not the case. I suppose some MOBOs, like those that allow you to update the BIOS without a CPU, can indeed display the BIOS on their own. In my case, the MOBOs were completely dependant on a functioning CPU.