Ok, if this sounds stupid, just tell me! I have just purchased a new mobo and want to check if it's in working order. I have no cpu, memory, drives or anything else except the case & psu. Can I safely test via on-board LED by connecting and switching power on?
The PSU will not work without a load on it i.e. CPU etc as it's what's called a switching Transformer. So without some means of putting that load on you cannot test it. What you mean is a bench test and it’s not worth buying the equipment just to test a MOBO