#1
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?
#2
I don't know what the problem is, it sounds a little weard to me. Maybe see a good guitar tech/luthier and have them tak a look.
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#4
Is this a new problem (how long yea had the guitar, are these new strings, old strings) if so it may be a dodgey string or as the previous post new strrings required.
#5
Check the intonation whilst fretting the 12th instead of the intonation. If the action is too high, The 12th harmonic will register differently to the actual 12th fret.
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#6
I'd start by double checking neck relief, doesn't sound like it's going to be that based on it only being 1 string, it's not likely my second check:

check the open string, fretted 12th, and harmonic 12th, they should all read (roughly) the same note, if they don't then you need to adjust the intonation at your bridge.
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