I see that this is becoming an old post but I wanted to add some testing that I’ve been doing on a 2011 Mac mini that was given to me. It exhibited exactly the same symptoms as other here are experiencing where the computer power indicator (sleep indicator?) comes on only for a brief moment when the the power switch is pressed. I’ve been working on this on and off for about 4 months… not wanting to give in.
I also noticed that as the unit was plugged in, the power indicator would flash momentarily even without pressing the power button. Other Mac Minis that I have do not do this. I did a number of tests looking for shorts and other irregularities on the logic board but found nothing. In the back of my mind, the GPU issue of the 2011 MacBook Pro was always present. And, there was a similarity with this and the HP G62 which suffered a similar fate. The computer would not start, but the caps-lock would flash.
I decided to add some solder past and do a reflow of the AMD GPU. At this point I really had nothing to lose because it didn’t work anyway. I applied almost 500 degrees Fahrenheit for 2.5 minutes using a rotating motion of a SMD station. After letting it cool down, I plugged in the Mac mini and the power indicator did not flash this time. Next,I pressed the power button and the computer immediately started up. It ran long enough for me to do a full installation of High Sierra. I let it run for a while and after some undetermined amount of time, the computer shut down on its own.
I was able to start it up again but I found it to be unreliable as it would crash and restart while trying to start up.
To sum this up, it appears clear to me that the reason so many of these 2011 models were no longer starting up was due to the failed AMD GPU. Of course, what I’ve done in no way is a fix. We all know that these GPUs cannot be repaired, but it appears to me that the GPU is the reason for the failure.
I challenge others that have the opportunity to do this same test, do so, and come back with your results.
OK, it looks like I have solved the problem at least on my Mac Mini. My Mini is a 2011 i7 with an AMD 6630M GPU. I can’t speak for other models that don’t have an AMD GPU, but I think if you have this same problem, it will apply. This problem is a fault on the logic board. I don’t recommend this repair for anyone that is not comfortable doing SMD work. It is best left to qualified technicians.
To do the repair, you will need to remove the logic board from the case and flip it over so the fan area and CPU side are facing down. Align the board so the USB, Thunderbolt, etc. connections are facing away from you. Locate the metal shaft on the board that is used for the long screw of the fan. Just to the left of it you will see a small capacitor with the white label “N8 de” and a “+” sign. This is the bad capacitor. It’s a 330uf 2v capacitor. I replaced it with a 330uf 6.3v capacitor, which is much larger. I used wire stand-offs to elevate the capacitor so it cleared other components. You are welcome to find what ever replacement works for you. The operating voltage of the VR is 0.99v. Be careful not to use high heat close to the memory chips that are along side this capacitor. I was able to replace the part by using only a soldering iron.
The Mac Mini is now working perfectly. It comes on properly without doing the quick on/off that is was doing before and I am very happy to see this working after looking at it on and off for the last 18 months. I wish you luck on yours, and as I say, be very careful when working on this. a mistake could be costly.