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My late 2015 iMac A1419 (EMC 2834) went black a few days ago. I removed the display and see the first two led lights on but not 3 and 4. I do NOT hear any chime but the fans spin up at high speed. I’ve tried an external display and get nothing. I’ve tried PRam reset and I’ve tried removing ram sticks. Same thing every time, no chime, lights 1 and 2 on, nothing else. Any ideas?
LED 3 - Indicates that the computer and the video card are communicating. This LED will be ON when the computer is communicating properly with the video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the video card might be installed incorrectly or need replacement.
You can get more information from this post Diagnostic LED - what order?
