Isn't the YLOD a power supply failure, or just a generic failure display? I forgot as I only knew 1 person to ever get it.
No, it's a problem that happens when either the CPU or GPU overheats. They used cheap solder (well, blame the European Union for banning lead-based solder in 2006) that can fail when the chip they're connecting gets too hot. The fix is to use a heat gun or something to reflow the solder. Even if it was only temporary, the fact that I got it working again at all by doing this says there's something to this.
It's actually fundamentally the exact same issue that causes the Xbox's RROD, ironically enough.
And actually, I wish it was the power supply. The power supply is easy to replace. I could do that in like 15 minutes.
What you need to do is run a backup as quickly as possible if you get that running again. Then, at least, you won't lose your save data if it permanently dies.
Not too worried about that, actually. I upgraded my hard drive only recently and still have the full system backup I did then. And after that I joined PS Plus, so I've got cloud saves.
No, I intend to fix this thing. Like I said, the fact that I got any results is promising. There are various things I can do better, like adding flux when I do the solder reflow. Unfortunately I'm off to vist family for the holidays pretty soon so it might have to wait until I get back.