Intel iMac Power up issues

[ryantp]

I am having an issue with my intel based iMac 20" For the past 2 nights my computer was unable to wake itself up from sleep, I was forced to press and hold the power button to shut down the computer. After having done that the computer would boot up fine. Last night about 2 minutes after the computer had been rebooted in that fasion the computer abruptly turned off completely and the fan started running. I let the fan run for about 40 minutes before I had to unplug the power cord to turn off the fan. Also while fan was running the computer would not boot. After waiting a 30 seconds I pluged the power cord in and pressed the power button. All that happened was the power light came on for about 3 seconds and the turned off. The computer did not attempt to boot, i.e. the drive did not spin up, nor was there any other internal noise. I then tried to reset the PMC by unplugging everything for 15 seconds and pressing and holding power while plugging in the power cord. Still get the same issue where the computer will not attempt to boot. Any suggestions as to what the problem might be, whether it is the PAV board or a power supply. I will try to re-install the RAM later in the day to see if that will help.