mac will not power on

Got it powered on. Just left it unplugged for about ten minutes then plugged it back in.

Thanks for your suggestions.

I did follow the control-option-shift instruction just before the successful power on, but I had the mac unplugged at the time. Don't know if the keystrokes made a difference, but I'm back in business.

Thanks again!

Thanks, Jack. I've tried that 10 second hold a couple of times. Usually I can hear the hard drive spin up, but I the Mac is completely silent right now.