Inconsistent intonation

[jowala]

I put together my build several months ago. I noticed an intonation issue at the time, but figured I'd give the guitar a few months to settle in before trying to tackle again. Well, it's still having the issue. This is a soloist body with a conversion neck and Floyd. My problem is that the intonation is wildly inconsistent. Far more than any guitar I have. When perfectly intonated on the open and 12, the first fret is about 8 cents sharp and the 22 fret is about 8 cents flat. It steadily goes from sharp to flat as you go up the frets.

Nut height seems fine. If I do the 3rd fret check, the string is practically lying on the first fret. I've just got a little bit of relief on the neck. I'm pressing as gently as I can on the strings while checking.

I don't expect perfect intonation across the fretboard, but none of my other guitars are even close to being this far off. Anyone got any idea of what's going on?

 

[supertruper1988]

what pickups? Or pickup config rather.

 

[jowala]

what pickups? Or pickup config rather.

HSH

 

[supertruper1988]

How are your pickup heights? if they are too close especially singles that can cause issues with intonation.

 

[TonyFlyingSquirrel]

I use a John Surh’s method of checking the 5th and 7th frets and making adjustments based on their info, finding the closest for all reference points. Unless you have a True Temperment fretboard, a standard guitar neck will never be “perfect”.

 

[stratamania]

I use a John Surh’s method of checking the 5th and 7th frets and making adjustments based on their info, finding the closest for all reference points. Unless you have a True Temperment fretboard, a standard guitar neck will never be “perfect”.

There is a typo, the 5th and 17th frets are what was meant, I think for checking the octave intonation.

 

[jowala]

How are your pickup heights? if they are too close especially singles that can cause issues with intonation.

Not very close. They're about 5mm from the strings.

 

[jowala]

There is a typo, the 5th and 17th frets are what was meant, I think for checking the octave intonation.

That's just kinda spreading the issue about, isn't it? From the 1st to 22nd fret there's about a 15cent difference. On my other guitars, it's about a 1-2 cent difference. We're not talking just a bit off. It's like the frets are literally in the wrong places. I might actually have to see if I can find a way to measure.

Edit: Broke out the calipers and compared it to another 24.75" neck with really good intonation. Everything was spot on. I'm going to try flatting the neck and lowering the action as far as I can and see where I end up.

 

[stratamania]

That's just kinda spreading the issue about, isn't it? From the 1st to 22nd fret there's about a 15cent difference. On my other guitars, it's about a 1-2 cent difference. We're not talking just a bit off. It's like the frets are literally in the wrong places. I might actually have to see if I can find a way to measure.

This method removes the nut from the equation and is a good place to get a reading for octave intonation.

Edit: Broke out the calipers and compared it to another 24.75" neck with really good intonation. Everything was spot on. I'm going to try flatting the neck and lowering the action as far as I can and see where I end up.

Also check that the pickups as previously suggested are not too high, as magnetic pull can put intonation out.

Other things that can affect intonation are high action, badly cut nuts, badly crowned frets etc. Badly crowned frets or those with too wide a land will throw off intonation, as it results in an effect like a fret being not positioned correctly.

 

[Rick]

After you've monkeyed around with it for a month, and you still don't have it, I recommend you bring it to a wizard ... I mean a good tech.