Has my power supply gone bad?

A few weeks ago my PC was having some trouble turning on, when I would power it on the lights in the case would come on, but it wouldn't actually power on. I would usually open the case up and dust it and fidget with a few wires and that would do the trick for the time being, but the problem still persisted. So I disassembled my PC and put it back together and it's turning on but now the graphics card isn't sending any information to the monitor and the keyboard and mouse aren't lighting up. I'm thinking it might be the PSU or perhaps the MB?