Bad SMC, CPU socket, sensors or logic board?
I recently replaced my late 2013 27" iMac logic board with a used logic board I got for cheap on eBay. The logic board was sold as fully working and pulled from a working unit, however the price seemed to good to be true (40 USD!).
When I got the replacement board, I noticed that several pins in the CPU socket were bent out of place. I spent an hour fixing them using a microscope to actually see what I was doing. When I was done, every pin seemed to be back where it belonged. After installing the board, it booted up fine, however the system was heavily throttled and the fan was constantly running full speed.
I took care of the fan speed with macfancontrol (which reports temperatures from all sensors normally) and of the throttling with OCLP. I already tried replacing the LCD temperature sensor, making sure that the system firmware is the latest and installing the original HDD, but without software patching, the system still acts up.
It's funny how whenever I plug the iMac into power, the breaker in my apartment goes out, but after restoring power, the iMac will boot up and work just fine (with the patches), going as far as pulling through several stress tests without any issues.
I'm pretty sure that the issue is logic board related and not PSU related, as the machine always worked fine with the original logic board until the point the GPU failed. Running apple diagnostics I got error PFM006 "there may be an issue with the SMC".
I'm curious to know if anyone had a similar experience or has any suggestions on how to fix this issue. I have some experience micro soldering dealing with small SMD components, however I don't have access to schematics and I don't think I'm comfortable working on a big BGA chip like the SMC, considering that the board is still kinda usable for the time being.
Update (02/03/24)
These sensors may not be working properly: unknown name
Update (02/05/24)
After replacing Q5575 (DIMM B proximity sensor) the problem was completely fixed!
Is this a good question?