I recently completed a PlayStation 3 Super Slim for a commission.
I had one on hand I got as part of a lot, tested it and saw no issues, so got to work cleaning her up and buffing out all the scratches from the case and getting the internals in good shape.
Put it back together, did a final test, and got the famed "green blink of death" which is very common on this model.
Unfortunately "common" doesn't mean easy to diagnose. Compared to something like the Red ring of death on a Xbox 360, which has detailed error codes, this might as well just say "broken ¯\_(ツ)_/¯". To make it even worse, randomly the system would turn on with no issues! I also didn't have a donor board to compare measurements with, which added another layer of complexity to the troubleshooting process.
After a LOT of probing around on the board, I found that the CPU was not consistently getting a full power load. On startup I would see anything from 0.2-1 volt. Combined with some online research I was fairly sure the cause was the PWM chip connected to the CPU, which controls the duration of the "on" cycles for the chip. Unfortunately, I didn't have another board to borrow one from, nor did I have a oscilloscope to actually confirm my theory, so in my quest to get this fixed I purchased another broken system.
After testing the chip, I swapped it over and was able to get consistent system boots.
Not really an economical repair, but it was a good exercise in troubleshooting as well as giving me an excuse to try out my new microscope and hot air station.
You can find more of this repair on my Instagram, and check out the send in form if you'd like your own worked on!