iMac Powers on then off, then on again no display?
I bought this iMac sometime back second hand. It worked great for while, then it got to be, that every time you wanted to use it, you had to reset the SMC (unplug it for a while & then plug it back in) Recently it has gotten worse.
Now when you turn it on, the first 3 lights on the logic board come on, then immediately lights 2 and 3 go off, then they all 3 come back after a few seconds. All 3 lights again are on and all of the fans are running at normal speed. There is no chime sound & nothing comes up on the LCD. I have hooked a keyboard to the iMac, attempting to reset the PRAM, however it still does no make a chime sound, I do know the usb is working because the mouse lights up when plugged into that socket. I am inclined to believe this is a bad logic board. Luckily I have several of these units and I changed out the power supply & lcd for testing purposes, same result. Curious to know what symptoms are usually present with a bad logic board. And more specifically, is there a component within the board that could be the culprit? Thanks