Question PC Won't Boot (Suspected PSU/Mobo) - Kind of Weird Issue ?

[mypcwontstart]

I'll try to condense this as much as possible.

One day PC wouldn't boot up wake up from sleep. All LEDs on system (Mobo and power switch) were on until I turned PSU off and on, at which point only the Mobo LEDs would come on, no luck with power switch. Shorted the power switch pins on the mobo, which got it working again, reconnected the power switch to the pins and no problems for a while.

A bit further down the track, same thing, except this time shorting the power switch pins did nothing. I was going to organise a PC tech to come pick it up but it randomly started working again so I cancelled that and it was smooth sailing again (this was probably a couple months ago)

Now, same problem, except shorting the pins won't do anything and it doesn't seem to want to fix itself this time.

Troubleshooting I have done:

• Shorting the power switch pins on the motherboard - no luck
• Removed everything but 24pin socket from PSU (modular PSU) and jumpstarted with a paperclip - PSU passed this test, so unless the PSU doesn't want to work under load it seems the PSU is fine.
• Reconnected the 24-pin socket to the motherboard and attempted to boot - still no luck. This is with only the 24pin socket connected to the motherboard but all components still connected to the motherboard, just not directly receiving power. Should I try again but with RAM, GPU, etc. disconnected? Doesn't seem to me like this would make a difference but I am no expert hence why I am here.

The weirdest thing to me is every time when my PC wouldn't boot my power switch LED would be on but pressing it wouldn't do anything, then when turning the PSU off and on the power switch LED wouldn't come back on. Also weird that shorting the power switch pins on the Mobo the first time this happened fixed it but the next two times nothing happened.

Specs in case it matters:
Asus TUF B450-PLUS Gaming AM4 ATX Motherboard
AMD Ryzen 5 2600 6-Core Socket AM4 3.4GHz CPU (with Wraith Cooler)
2x8GB G.Skill FlareX 3200MHz DDR4 RAM
Galax GeForce GTX 1660 Super
Western Digital Green 240GB NAND 2.5in SSD (Operating System Drive)
Western Digital 2TB Blue 3.5in SATA HDD (Storage Drive)

Don't have a multimeter or and spare parts to test with. Main suspect to me is the motherboard, but I guess maybe the PSU has decided it doesn't want to work under load all of a sudden too. My next step is probably to take it for repairs but I am guessing all they will do is test with a known working PSU/Mobo and diagnose one of them as the issue, but again I'm not sure. If any of you have any ideas, fire away! Appreciate any and all help/suggestions, cheers.

 

[Fix_that_Glitch]

Makes cheapest sense to test the psu under load to exclude it. If it works, then your motherboard needs Rma/replacing.

 

[mypcwontstart]

Makes cheapest sense to test the psu under load to exclude it. If it works, then your motherboard needs Rma/replacing.

How would I do that? Reconnect all the components to the PSU and power it using the paperclip method?

 

[John Chesterfield]

Reset CMOS?

 

[mypcwontstart]

Reset CMOS?

Just put the battery back in after leaving it out for about an hour, but too tired to continue troubleshooting. Will see if that fixes anything in the morning.

 

[mypcwontstart]

Tried resetting CMOS as a last resort, no dice. Really suspect it's a faulty motherboard but as I don't have any spare parts laying around will send it into a shop for them to look at.