Chosen Solution
So I decided to upgrade my iMac with a blade ssd. I followed ifixit guide carefully. Everything went fine, there were no trouble at all, so I decided to put a new thermal paste in the cpu while i’m at it. The reassembly of the cpu didn’t go as smooth, but I did managed to assembled it. But as I reassembled the machine, the iMac wont boot up. There is no sound coming from the iMac. The LED #1 on the logic board is lit, but nothing on the others when I push the power button. My initial thought is that I have toasted the cpu, as it was the only step I had trouble with. Worst case scenario is that I have toasted the logic board. Is there anyway to check which unit is the cause of the power up failure? Can I assume that the power supply is fine when there is light on the LED #1? Symptoms before the ssd upgrade: The iMac had trouble waking up from sleep. It went on “hibernating” mode and it took a while to start up again. I tried pram and smc reset andd it didn’t help. Which is one of my reason to upgrade to ssd.
Did the CPU have pins? If so you may have accidently bent one. Generally, if it was heat related the computer would have run a short while and then automatically shut down. (An aside - You may also have put on too much paste)
No, do not assume the power supply is good. All you know now is that the power supply is receiving juice. If #2 lights up then you know the PSU is good. So that’s the first thing to check out and make sure all your connections are secure. On this model the PSU is the most common failure in my experience. iMac Intel 27" EMC 2546 Power Supply Replacement
Did you ever get a resolution? Almost identical scenario just happened to me, I find it hard to believe its the PSU, simply because before the repair (literally 3 hours ago, the computer booted perfectly fine. Only 1 led turns on, I get nothing, I’m borderline devastated. I loved this thing! Help! Thank you in advance!
