Tech: Guitar Intonation Problem

Subject: Tech: Guitar Intonation Problem
From: Dewey
Date: 22 Jun 07 - 01:43 AM

I have a 1970 Gibson J-50 Acoustic that recently has been buzzing on me. There is no visible damage to the neck, i.e. no cracks or reglued parts anywhere. So, I took it to a friend that works on guitars. He put a new bridge saddle piece on it which corrected the buzzing, but now there are intonations issues in certain regions on the neck. Sometimes when the guitar sits its sound fine everywhere, but after one starts playing and tuning the instrument its starts into playing sour on either high regions of the neck or in the first three frets.

Any suggestions as to what might be up with this problem and how I might correct it. The friend I took it to said there is nothing he could do about the intonation issue and he didin't want to fool with the neck.

I absolutely love the tone of this guitar. And would do almost anything to it to get it back as a playable instrument. I'd even consider puting on a new neck if that might help.

Please respond if you know what might be some of the causes of this intonation issue; and, if you might have some advice as to how I might get the instrument restored to its prior condition.

Thanks!

Subject: RE: Tech: Guitar Intonation Problem
From: ThreeSheds
Date: 22 Jun 07 - 02:42 AM

Duff or old strings can cause intonation problems, is the the saddle compensated there is a limited amount that a saddle can be compensated. Is the bridge in the right place? the twelth fret should be bang in the middle of the string length

Subject: RE: Tech: Guitar Intonation Problem
From: mandotim
Date: 22 Jun 07 - 03:05 AM

It might be worth checking the nut setup. Sometimes the string binds in the nut slot, and sticks when tuning. Try stretching the strings by hand, and tuning back and forth a few times before tuning to pitch. Run a pencil lead through the nut slots as well; graphite is a good lubricant. Are the nut slots cut level? If the string is bearing on the back of the slot, this can throw the intonation off. Did your friend mess with the truss rod at all too change the action? Duff strings (as above) are another common cause.
Good luck.
Tim

Subject: RE: Tech: Guitar Intonation Problem
From: Bernard
Date: 22 Jun 07 - 04:21 AM

The first thing to check after you put new strings on is that the 12th fret harmonic gives exactly the same note as fretting the string at the 12th fret.

If both are not exactly the same you will get intonation issues.

If they are exactly the same, and you're still getting intonation issues, you may have problems with the neck alignment as noted above.

Subject: RE: Tech: Guitar Intonation Problem
From: redsnapper
Date: 22 Jun 07 - 05:13 AM

Usual things to check are: saddle height, string break angle over the saddle, string bearing position on saddle, string height at 12th fret, string bearing position at nut, binding of strings at nut or saddle (e.g. due to wrongly cut nut or saddle slots - can sometimes be helped by lubricating with graphite as mentioned above), neck relief (e.g. due to incorrect truss rod adjustment), incorrect neck angle, slipping of strings on tuning posts, tuner gears slipping and most obviously and first... are the strings giving correct intonation (old strings will often give tuning problems and new strings sometimes take a while to become fully stable).

It sound to me like this is an easily solvable problem by a guitar setup specialist (not necessarily the same as a luthier... I have worked on badly setup instruments from otherwise excellent luthiers). Often correcting the problem will mean looking at several, and sometimes alll, of these parameters.

RS

Subject: RE: Tech: Guitar Intonation Problem
From: Grab
Date: 22 Jun 07 - 07:29 AM

One thought if the problem seems to be intermittent - check your left-hand technique. If you're pressing too hard, the notes will go sharp. I might be teaching my grandmother to suck eggs here, but it's worth mentioning, especially if the new saddle is a different height to the old one.

Graham.

Subject: RE: Tech: Guitar Intonation Problem
From: GUEST,highlandman
Date: 22 Jun 07 - 08:46 AM

I have an early 70's J-50. All the comments above are correct, especially those concerning strings.
Neck stability is also an issue with these instruments. I find I have to tune ever so slightly differently for standing (with a strap) vs sitting, and have to keep a fairly consistent body position when playing. It's easy by changing the position of your elbow to slightly twist the neck and get the intonation a bit sour.
Caution: when you check the harmonics as described above, you of course are not putting any stress on the neck, so you aren't checking in the same condition you're playing. Which means that even the best setup person can only work so much magic without having you in his/her shop to play the instrument and set it up for your personal style.
I fiddle with mine all the time because I play in quiet environments mostly, use a lot of open chords with fingering up the neck, and I have a persnickety ear. One thing I've learned is to temper the 2nd (B) and 6th (low E) string a tad flat open. The next thing I may try is a saddle compensated on the B string.
Good luck
-Glenn

Subject: RE: Tech: Guitar Intonation Problem
From: GUEST,Aoliandorian
Date: 22 Jun 07 - 02:31 PM

It is also worth cheching the thickness of the new bridge insert. Older guitars tend to have slightly thicker inserts and so will aLter the parameters for string length. I make my own from bone blanks (for a 1987 Martin D18 dreadnought, usualy played in DADGAD).
On a general note, always try to get advice from someone who plays in a similar style to youself as they are likely to have the same problems.

Subject: RE: Tech: Guitar Intonation Problem
From: Dewey
Date: 23 Jun 07 - 08:27 AM

Thanks everyone for the info. I love this guitar and hope to get it back in tip top shape. I am a bluegrass crosspicker and flatpicker, and pretty much use all of the neck and strings in rapid procession. The sound of this guitar has always been thick and bright and not boomy like a martin which suites my particular playing need.

Don't want to have to lose this guitar to intonation issues, as it would be difficult for me to replace it.

I will look into all of the above recommendations with painstaking care, as I have already experienced many of the same issues that everyone here has already been discussing: mainly problems with dullness in the b-string, having to tune the low e string flat, and having to wait for the neck and strings to "settle in" to correct the intonation instability.

Many thanks, once again, to everyone of you, for you expert help and advice in hopefully getting my favorite guitar back into good sounding, as well as, good playing condition.

Subject: RE: Tech: Guitar Intonation Problem
From: McGrath of Harlow
Date: 23 Jun 07 - 06:58 PM

To check if the problem is with the nut (which I suspect won't be the case), just try putting a capo on the first fret and see if it the trouble reoccurs.