Rev. A iMac 17″ G5 1.6GHz doesn't sleep or power up consistently | The Nanchatte Technojunkie
2013 imac 21.5” power issue, replaced power supply twice, still no diagnostic LED on. The Mac will power on after being plugged in for several hours. And then powers on like nothing
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SOLVED: Where are the diagnostic LEDs on the iMac mid-2011 27" EMC 2429? - iMac mid-2011 27" EMC 2429 (2.7GHz i5) - iFixit