Question PC froze and now unresponsive when powered on.

[openclosed1]

So I was using my PC (2 years old that I built) and it suddenly became unresponsive. I did a hard shutdown and then when I tried turning it back on it wouldn't boot. The PC turned on, the USBs and LEDs became active and the fans revved up but there was no visual on the monitors. The keyboard and mouse do not turn on but I tested those USB ports do work with an external HDD.

Here's what I've tried so far:
Moving the monitors wires from the GPU to the motherboard.
Removing the GPU, a capture card, and USB PCI expansion devices.
Removing the CMOS battery for 10 minutes and reseating it.
Removing the RAM and trying one stick at a time in each different RAM slot.
Double checking all the mobo wires to make sure they are fully seated.

There is no BIOS screen, the monitors act like there is nothing connected to them at all even with the PC running whether they're plugged into the GPU or the mobo. The keyboard and mouse also act as though the PC is not on even though the ports work. I'm fine with buying a replacement part but I don't have test parts lying around so I need to figure out how I can narrow this down. I would think it is the mobo, but I don't know how to really confirm that. Would the CPU going bad have this effect?

 

[lvt]

Does the monitor works on other PC / TV?

 

[openclosed1]

Yes and there's two of them that were working at the moment the PC froze.

I also thought about it more and the PC had been acting kind of strange leading up to this. It had froze the day prior (which is very unusual) but it came back after hard reset. Also the past week or so selecting sleep mode or power down in windows didn't work properly. Like it would shut the monitors down but the PC would still be running and I'd have to hard power it down with the button in order to shut off the PC.

 

[lvt]

So now it's time to check the PSU and motherboard.

 

[openclosed1]

So now it's time to check the PSU and motherboard.

Yeah that's the problem is I don't have extra parts to swap so I'm not sure how to narrow it down. I can afford to replace one of these parts but not all of them. I'm leaning on it not being the PSU since everything is powering on (though it is still possible). I've looked into it further and the CPU could be the culprit as well so I need to figure out if it is the mobo itself or the CPU.

 

[lvt]

Ideally you should have an ATX power tester, it costs $10 online and can saves you a lot of time.

 

[openclosed1]

The PSU doesn't seem likely so I guess I'll just roll the dice and get a new CPU