One of our 2012 iMACs began behaving oddly the other night. Son had me come look at the screen and it was stuck at the Apple logo screen with a few vertical lines on it. I had him power it off until I could get to it. I looked at it last night and it won't power on at all. So, I am guessing it is a bad power supply, or possibly switch? I was hoping it would be something simple like needing to reset the firmware or the like. However, it doesn't do anything. What can I do next to troubleshoot. Should I go ahead and order a power supply to swap out?