My old computer died, so I decidied to replace some core components to make a new one - CPU, GPU, motherboard, and PSU. I used chaud's recommendations from a month ago and got a XFX XTR 750 as a PSU and a Z97-A motherboard. The issue I'm having is that I can't get the motherboard to power on properly. If I attach just the 24-pin power supply the computer turns on okay (although it won't provide any monitor output), but when I attach the 8-pin ATX power supply as well the computer starts to spin up, but then it makes a grinding noise and halts and the red CPU light on the motherboard displays.. and then it just restarts itself over and over. I'm at a loss for why this is happening - I have all the RAM and the GPU removed (it does the same thing if I put them in), but I'm not sure if I'm just doing something wrong regarding the build or if there's a problem of one of the pieces.
I'm not seeing much online about what this red light / restart issue means that can be relevant here... it just strikes me as odd that the computer turns on fine without the 8-pin supply but then it dies when it's attached. Any advice on how to approach this before I have to take the computer to a shop?