I am having a strange situation with a Dell Optiplex 755 machine. This was sitting idle on a shelf for some time (it is part of our reserve loaner PC pool). Today, I had a need for it. When I took it off the shelf and plugged it in, it immediately began to churn up even though I did not hit the power button. Stranger still, when I went to cold boot the PC (by holding the power button in for a few seconds) it would power down only to rev up again once I took my finger off of the button. Howver, all I get with all this is an amber power light with no POST or loading of Windows that I can see.
The PC is out of warranty, so I cannot contact Dell as I would usually do.
I am thinking that this is either a bad motherboard, power supply, or both? I would appreciate any additional troubleshooting steps in order to determine.