So if I just buy a small seperate PSU, how do I go about connect different things to it? Will it run by itself, not connected to the MOBO? Sorry, I admit that I am ignorant when it comes to electronics. I've never built or modified a PC.
Oh, the things I'm planning on connected are a few fans, maybe an LED bar and a coin mech.
You need to short pins 14 with 15 or 16 as far as I remember. That was the green with either of the blacks beside it! This will make it turn on when you plug it in. Otherwise it will sit dead.
Then take any of the yellows for 12v and black for ground. If you want 5v, just use red, and black for ground again. Simple as! Just make sure not to short the cables.
A tip for installing fans! A fan will only spin when connected the correct way, therefore before installing it, plug it in to your 12v and ground and reverse cables if necessary to get it moving, only then install it. Reason is, I installed mine, then wired them, but figured out they were blowing the wrong direction and had to remove and reinstall the opposite way!
(Disclaimer: I have blown up a few items over the years but this worked for me)