Question PC suddenly won't POST - Suspecting dead MOBO

[SiamLights]

A week ago I got a replacement RAM and PSU for my PC. Before I'd been using a generic 600W PSU that came with the case as well as some generic RAM sticks for about a year and a half. This was the first upgrade I was able to afford because of Corona.
Before bed I usually turn the power switch off on the PSU and unplug it in case there's a power surge, but it wouldn't boot this morning. However, USB devices work properly, I'm able to charge my phone and my pen tablet recognizes if I get the pen close to it. I've jumped the PSU and the fans would spin; I tried booting with 1 stick of ram and jumping the MOBO power pins, neither would boot either. How can I rule out both MOBO and CPU, considering both are the ones I've yet to troubleshoot?

This is my build:

• XPG Pylon 450W
• Kingston Fury 8x2 3200Mhz RAM
• Ryzen 2200G
• B450M DS3H (rev 1,x)

I have tried:

• Reading the manual for my PSU and MOBO
• Verifying that standoffs are installed
• Plug & unplug USB devices.
• Reseating RAM
• Clearing CMOS
• Plugging & unplugging PSU power connectors
• Jumping PSU (Fans would spin)
• Jumping MOBO (No response)
• Booting with 1 stick of RAM

My MOBO came with no speaker or led lights, so I can't debug that way. Thanks in advance.

 

[DRagor]

I've jumped the PSU and the fans would spin

That test only matters when it fails. When it works you still know nothing. Still have that 600W one? Try it to make sure it's not a PSU problem.

How can I rule out both MOBO and CPU, considering both are the ones I've yet to troubleshoot?

Generally you can't. You can more or less rule out every other component through tests but when it goes down to mobo-CPU there is no way to tell which one is faulty (at least as far as we talking no boot problem).

 

[geofelt]

Why did you change a 600w psu for a 450w unit?

 

[SiamLights]

Why did you change a 600w psu for a 450w unit?

The 600W was a generic one, a quick google search told me it had no protection for power surge, undervoltage, blackouts, no 80 Plus rating etc. It was a ticking time bomb.

 

[SiamLights]

That test only matters when it fails. When it works you still know nothing. Still have that 600W one? Try it to make sure it's not a PSU problem.

I'm kinda hesitant on putting that one back, the fan made some hellish noises and I'm kinda worried it might've been the catalyst for these problems, but I'll give it a try to see if it posts.

Generally you can't. You can more or less rule out every other component through tests but when it goes down to mobo-CPU there is no way to tell which one is faulty (at least as far as we talking no boot problem).

I have no one I can swap parts with either so it's gonna be a bummer if I swap the MOBO and it ends up being the CPU. Fingers crossed.

 

[Lafong]

If you KNOW it's either CPU or motherboard failure, it's VERY likely it's a motherboard problem. CPU failure is exceedingly rare.

 

[SiamLights]

I did a test with a multimeter on my MOBO and PSU. Everything seemed to do fine other than the CPU Fan pins. Pin number 4 yielded no continuity. The PW+- and RES+- didn't either.
Both the 450W and 600W PSUs passed the test with flying colours

I'm guessing this makes the MOBO more suspicious as responsible. Still hoping it didn't take the CPU out with it. I still hope I can get more insight from you guys; thanks again and merry christmas.