Question New PC build won't post

[Andrew_in_JP]

PC specs:
CPU: Ryzen 5 3500
GPU: Sapphire Pulse Radeon RX 5600 xt
MOB: Gigabyte B550 Aorus Elite ATX
RAM: 8GB 3200 Patriot Viper Gaming x2
PSU: Corsair CX Series 80 Plus Bronze
SSD: Addlink 512GB S70 M.2 2280 PCIe3.0×4 NVMe

When I power up the PC all the fans and LEDs turn on, but get no display. I installed beep speaker, but don't get any beeps. I've triple checked all power connections to CPU and MOB. I assume the problem is either CPU, MOB, or PSU. I don't have any spare systems and don't know anyone who could help me troubleshoot parts.
I was wondering if anyone had an idea to narrow it down more.
Also when I had everything installed all the fans and lights were running, but with the RAM pulled out the GPU fans don't turn on and some LEDs. Not sure if that really means much.

Thanks in advance.

 

[rgd1101]

using dp/hdmi/dvi on the gpu?

 

[Andrew_in_JP]

using dp/hdmi/dvi on the gpu?

HDMI. It doesn't have dvi and I don't have a monitor that uses dp.

 

[agentprime]

you should check your psu
you can look in YouTube to check how to check an psu is working or not

 

[Andrew_in_JP]

So bought a meter and the PSU is working just fine.
Is there anyway to check the motherboard separate from the CPU to see if it's working?

 

[GarrettL]

A psu has to be checked under load.