PC not booting

[Totallyruledup]

Hi all,

 

I've recently been trying to bring an older PC back to life with some new parts, upon replacing all parts I have come across the issue of it not booting. I have read over the topic regarding this and can't seem to pick out anything that could be the problem, I'm very amateur when it comes to stuff like this. I plugged everything into it's correct spots and attempted to turn it on. The motherboard is a TUF-B450M-Plus II , when powered from the PSU the motherboard is showing it's LED's on the back which I would assume means there is power to the motherboard. When I go to turn it on the power button lights up for a second and goes straight off and none of the parts in the PC boot at all. One quick thing I noticed when inputting all the cables was that my PSU only had a 4 pin power connector but the mobo has an 8 pin slot, I gave this a quick google and came across the answer of as long as the mobo doesn't require that much power it should still run. 

 

Quick idea of specs

Mobo - TUF-B450M-Plus II

GPU - GTX 750ti

CPU - AMD Ryzen 3 2200G 3.5ghz Quadcore

RAM - Crucial 16gb DDR4 3200

 

Any help at all would be greatly appreciated, I will answer all questions I can  

[bulgarian man]

Check if your ram is plugged correctly. It could be the BIOS. 

Is the Cpu cooler working?

There could be cable which is responsible for this. There are a lot of things that could be. 

[Totallyruledup]

Ram is slotted in fine, unsure about the cpu cooler as the pc doesn't even start up

[Alan G]

What is the PSU you are using.  I once had a PSU fail when the Power Good signal suddenly went out of spec and the results were the same as what you are seeing.  When I put in a new PSU, the issue was solved.  I have one of those inexpensive PSU testers which work pretty well and give accurate voltage read outs in addition to the PG signal.