I'd just like to share how I was able to fix the issue outlined in the original post (about the SMC Bypass).
If you want a TL;DR: The problem was with the POWER CORD! Replacing it was the solution for my situation.
My father's Macbook (model A1226) was working fine for years, when all of a sudden it stopped booting. After some research I discovered the mysteriously undocumented SMC Bypass method. It was the only way the computer was able to start up. If it ran out of power we had to run through the whole process of holding down the power button for 10 sec, without letting go plug in the power cord, etc. Basically it was the exact issue addressed by Dadioh in the original post. My father is pretty stingy with his money (the price of a new logic board was too high for a computer that "worked"), so I ended up writing down the SMC Bypass instructions on a sticky note on his computer. He happily used it in the annoying bypassed SMC state (fans running full speed, battery indicator not working, etc.) for several months...
Anyways, after reading some of these posts I was certain that it was a logic board problem, specifically an issue with the SMC chip. As Dadioh suggested, I pulled out the logic board and inspected it for any spill damage (or visible damage of any kind). There was none, it looked pretty much like a brand new board.
At this point I should have probably checked the G3Hot voltage and all of the other multimeter fun outlined here, but I didn't. I was short on time and just told him that he definitely needed a new logic board, which would be around $80-90. As a last-ditch effort I decided to reflow the solder in this logic board with my heat gun, since there was nothing to lose (he ended up buying a new computer before this point :l). Long story short, the reflowing did no good (but didn't destroy it either
).
I was about to give up, but I decided to try the power cord (Magsafe 85W) from my mother's much newer Macbook. Astonishingly, using this cord everything was suddenly fine, the SMC Bypass was no longer needed (unless I switched it back to the old power cord)!
After some inspection I found that the cord he was using (which functioned perfectly for over a year) was rated at only 65 Watts, while this model of Macbook requires an 85 Watt power supply. Could this be the problem? I'm not sure, I don't have another 65W power cord to test with.
So that was my solution.. Maybe we should condense down all of the potential solutions to this problem, as it appears to be a symptom of multiple different hardware issues.
Here is the solution list for this problem as I understand it.
If the only way to start your Mac is the SMC Bypass, you should try these steps:
- If the battery in this computer is also dead and won't charge, verify that the power cord you are using provides the proper Wattage. If it does not, obtain one that does or try a different charged battery with the power cord unplugged.
- Check the logic board for signs of spilled liquid. If there is, clean it off with 99% IPA and a toothbrush.
- ... Your solution here.
Let's try to get the solutions to this issue properly documented!
Edit: I should mention that his battery was completely dead. If your battery still holds a charge, I don't think this solution would work for you, as you don't need a power cord to boot it in the first place. (Although I am really not sure about this, it just seems to make sense.)
