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Konrad
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3 LED diagnostic lights, no startup chime, blank screen
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My 2.4 GHz 24-inch Intel iMac stopped working after a bad storm. Starts up, but no internal or external monitor screen. There is a slight burn odor. Other site answers on this problem indicate that three LED diagnostic lights and no external monitor function mean a bad logic board. I bought a replacement logic board with no change in machine behavior except there is no startup chime. I can hear the HD (now reformatted and blank) and CD/DVD drive running, but screen stays blank. Hooking up an external monitor does not work either. What's the next step? The logic board was expensive enough. I don't want to keep replacing parts willy-nilly until I would be better off buying a new iMac. Sure could use some helpful advice.
More information. I swapped the power supply and screen from an identical working iMac. There was no change in the symptoms. So, does this point to the graphics card or could it be something else? Thanks in advance for your help!
Konrad,
No Answer (gosh) - but i have the same problems with a identical machine right now. Any hint would be gratefully appreciated.
remacberlin,
Installed a working graphics card onto the original logic board and reinstalled into the iMac. System booted just fine with all four LED lights shining and complete screen function. This indicates at least in this case that the advice given elsewhere that the lack of a fourth LED means a bad logic board is not correct. Be aware!
Konrad,