#1
I have an '82 Peavey T-25 that has a serious intonation problem. I have the truss rod and neck angle, adjusted to good action up and down the fretboard. The problem is that if I set the intonation between the open string and the 12th fret, every string is very sharp at the first fret (enough to make open chords sound way out of tune). Checking up the neck shows that the first fret is very sharp, the second a bit less sharp, the third even less, etc. The 13th fret is a little flat, the 14th a little more flat, etc. I'm pressing the string just enough to fret the note, so it's not too much fretting pressure.

The tops of all the frets look very flat, with little or no crown. This isn't fret wear per se, they don't have little wedges worn into them, more like they were filed flat for some reason.

If the frets are low and flat, would they cause this progressive intonation problem? I can get the 12th fret right, or I can get the 5th fret right, or I can get the 1st fret right, but there's no way to get the whole neck right.
#2
Quote by jds2

If the frets are low and flat, would they cause this progressive intonation problem?


very slightly but it would not be as progressive nor as consistent and as "off" as you describe and is more noticeable on jumbo frets. sort out the basics first before the obscure.

what was wrong with the angle of the neck and how did you set it? and why? and how did you measure this? i'm getting the picture of an overall change in compensated scale length here.
Last edited by ad_works at Dec 14, 2015,
#3
Quote by ad_works
what was wrong with the angle of the neck and how did you set it? and why? and how did you measure this? i'm getting the picture of an overall change in compensated scale length here.


With the truss rod adjusted correctly, the action was very high, especially much beyond the 4th fret and progressively worse down the fretboard. Peavey's have a micro-adjust Allen screw that can be turned in to push the leading edge of the neck away from the pocket to bring down the action. I turned this in until I got the low action I wanted with the bridge height near its lower limit. This was the recommended procedure in the Peavey instructions.
#4
If your action is very high and if your frets are low and flat, you will have issues with intonation.
You've stated you have "good action" -- what, exactly, are you calling "good action?"