OK so i have a 79 les paul and my b string won't stay in tune above like the 9th fret. i understand how intonation works but if i check the open string against the 12th fret harmonic, they register the same (both in tune). could this still have something to do with my intonation or maybe a whole other problem? im kind of a n00b when it comes to guitar repair but i know the basics (and i really don't have $$$ to pay someone to do it)
You have to fret the note at the 12th fret. The 12th fret harmonic will always be an exact octave of the open string, no matter where the saddles are set.