Chosen Solution
I’ve just had my iMac’s GPU reballing done, and after reassembling the system, when I press the power button I can hear the fans and hard drive spinning, however, no startup chime or image displayed. Only the first diagnostic LED is on. I have already tried using different RAM sticks as well as an external display. Any ideas on what can it be?
#1 LED only, on indicates a failed power supply, probably a partial failure. If #2 was on, I’d say the GPU, but its not!
Sadly I think your GPU card had failed. I would try a known good card to see what happens then.
