@Pink_Hat: it’s probably going to take some trial and error.

Try starting it with a CD in it and then without (try a different disc)
Try starting it while it’s lifted at an angle
Try cleaning the optical lens with the right solution
Try pressing those buttons again?
Other than that you could try looking into this
https://www.ifixit.com/Wiki/PlayStation_Troubleshooting

@vex714: Update 2: didn't help, back to square one

@vex714: Already done pretty much all of that, I've pretty much narrowed it down to being something on one of the PCBs. I spend hours just messing with all those things and more the day I got it, but nothing ever seemed to do the trick. But I have a few things left to try, so hopefully those'll do it. I just wanna see this thing work so bad

@vex714: Update, I took it a bit more apart and discovered what seems to be an old soda-spill in the serial port or something, the underside of the main PCB is all yucky, so now I'm giving it a thorough clean in the hopes that it'll help