Last month I left my PC on and I walked away for a moment. I come back and although my PC is still on, there is nothing on the monitor and it is not picking up an HDMI signal. At first I thought it was the monitor (which is only 3 months old ASUS VE228), but it detected my laptop's signal just fine. My two-year-old son was around it and my girlfriend was near him, but wasn't paying much attention to him and he likes touching my PC when the lights are on. Before I jump to conclusions and blame the little guy, I search online for some information and someone suggested that my PSU most likely crapped out.
My PC would still turn on, light up and run all fans, but I purchased a cheap power supply tester and tested my PSU. The tester was made in China and the English instructions were confusing, so when I heard the piece of crap give a continuous ring--which the instructions called a "DuDu ring"--I thought my PSU did in fact crap out. I end up purchasing a new PSU (EVGA 500B).
My PSU comes in the mail, I hook it up and my PC does not even turn on. My CPU fan turns just slightly and that's it; no lights come on and no beeping. I tested my new PSU and it works just fine. I think my motherboard was slowly dying and now it is completely fried, but I need a second opinion.