Chosen Solution
Hello, I followed your guide and replaced the HDD with a SSD in my iMac (late 2013 A1418 21.5” 2.7 GHz). Everything was pretty easy, however my screen is now completely black. Makes chime when I turn it on. LED diagnostic lights 1-3 are on, but 4 is off. External monitor works fine, and I used this to set up the new SSD (evo 860) and install MacOS. One thing I noticed was the iMac seemed slower, not what I expected after adding a SSD. Also after the hard drive replacement the fan was constantly on full blast. I downloaded Intel Power Gadget and confirmed my suspicion that my CPU was capped at 0.8 ghz, as opposed to the 2.7 it’s supposed to be. I assume the display must have a thermal sensor and because there is no communication the fan speed and CPU throttling are occurring as a result of this? I downloaded the Macs Fan Control app and all the reported temps are good and I can use the app to adjust the fan. I was hoping worst case scenario I could still use the Mac with an external display, but 0.8 ghz would drive me nuts. I examined the logic board, cables, and connectors closely, and noticed the corner of the LVDS cable was slightly damaged. I purchased a replacement, but still no luck. The replacement cable could also be bad I suppose, but seems like wishful thinking. Could the damaged cable have caused something else to short? Is there anyway to get around the throttling so I can use an external display? Here is a picture of the damaged cable and my logic board.
Thanks - Cory
Sadly, you did some damage to the logic board. At this point you’ll need to bring your system to someone with micro-soldering skills and tools as well as has the needed parts to fix your logic board. The other option is just replacing it. iMac Intel 21.5" EMC 2638 2.7GHz i5-4570R Logic Board and here’s the guide iMac Intel 21.5" EMC 2638 Logic Board Replacement
