Intonation problem with my new Ebay purchase

[mandotrev]

Peculiar problem with this '51 Levin that I got on Ebay. The neck looks perfectly straight to me, but it's sharp on the 3rd fret, less so from the 5th to the seventh fret, and is in tune at the 10th fret. An open G chord sounds less than in tune. As you can see, the action is high, which I am concerned about because the seller represented it to be 3mm at the 12th fret. I think she was measuring before the strings were tightened. As you can see, it is considerably higher than 3mm. No bowing, though. all the seams are perfectly aligned.

I used an electronic tuner to position the bridge. I moved it back about 1/4 of an inch from its original position to get a perfectly tuned octave at the 12th fret and then moved it around slightly to see if I could find a spot where the intonation was best. It has improved a little with playing for a couple hours (or is that my imagination?). The first three pictures were taken just now and the last group of pictures are from the seller's listing on Ebay.

The instrument does not appear to have been played much. The gears on the tuners look fairly new, even though the instrument is sixty years old. It is quite loud and has a nice tone, so I hope I can fix the intonation issue. I paid $250.

Any ideas?

[Tavy]

If it's in tune when open and at #12, but not when fretted on the first few frets then either:

1) The action is so high that the strings bend sharp when you fret them, or,
2) The point of contact of the strings on the nut is not at the leading edge of the nut, but further back. Use a magnifier and look closely at how the strings pass over the nut, often if you have this issue it's the G strings that don't sit down in the slots right.

A trip to a local luthier to have it properly set up would make the world of difference (3mm at #12 is much too high IMO), otherwise the resources here and at frets.com should get you started in adjusting the nut and bridge towards a more playable condition. Judging from your photos, the nut doesn't look too high (can't tell if the strings are touching in the right places though), so I suggest you start by lowing the bridge - remember you have to remove 2mm from the base of the bridge to lower the action at #12 by 1mm - if you start by lowing the bridge to give an action of around 2mm you should be fairly safe as long as the neck's straight and the frets are flat!

HTH, John.

[8ch(pl)]

You may be better served by getting a series of new bridges made up. They are not that hard to make. If you take a look at the Red Henry site it will give you some ideas. The Levin, being a Flat top will be easy to fit.

[mandotrev]

Thanks for the advice, 8ch and Tavy. The nut looks okay to me. I am thinking of filing down the bridge myself. I own a big metal file. Is there any reason I shouldn't try it?

[gregjones]

I think you would be better off with a piece of sandpaper, maybe around 200 grit on a flat surface, I use the glass top on Cheryl's coffee table. Frets.com has pictures of sanding a guitar saddle----same idea.

You don't want to prune the rose bush with a chain saw.

[Jim Garber]

I think you would be better off with a piece of sandpaper, maybe around 200 grit on a flat surface, I use the glass top on Cheryl's coffee table.

I would hesitate to use a completely flat surface to sand the bridge bottom. Even tho it is a "flat top" mandolin I am sure that there is some induced arch to the top.

[Tavy]

I would hesitate to use a completely flat surface to sand the bridge bottom. Even tho it is a "flat top" mandolin I am sure that there is some induced arch to the top.

Agreed: that said for bridges that are ridiculously high, you can sometimes speed things up by using the chain saw (big file in this case!) to speed things up... but if it's the first time you've done this, then I would suggest sandpaper on a flat surface first off, then when the bridge is somewhere near it, place the sandpaper on the instrument top and sand it to fit the instrument. BE VERY CAREFUL when you do this! I place a couple of sheets of transparent pastic bag between the top and sandpaper to help protect the top, but even so it's easy to get carried away and mark the top. Use fresh sandpaper, sand gently, and let the paper do the work. Also don't reply on this post (or any other) for instructions... go to frets.com and check out the guide with photos etc: it's for fitting a bridge to an arch top, but the procedure is the same. I've owned a couple of "flat top" instruments that had the top cracked and out of shape because a previous owner had a badly fitted bridge, so it really is important to fit to the instrument.

HTH, John.

PS re sandpaper grits: 200 may be fine for rosewood bridges, but for ebony you may need a lot coarser than that or it'll take a very long time...

[DerTiefster]

I think you should be very careful about starting any process involving removal of material until you are pretty confident that you know the malady you are trying to remedy. If you try modifying the bridge to fix something caused by a bad nut, you are destined for disappointment. Make sure you know what is happening to make the instrument sharp on the lower frets.

[mandotrev]

I agree, but I don't know what else to do. The nut appears to be okay, and the action is high anyway, so it won't do any harm to shave off a millimeter or two, IMO. What diagnostics can I do to check if it's a bad nut?

[mrmando]

Could be an improperly slotted fretboard, he said with an evil chuckle.

[David Collins]

Could be an improperly slotted fretboard, he said with an evil chuckle.

Happens a lot more than most would like to think.

A more thorough evaluation is difficult to do without having it in hand, and there's not enough info here to give much of a good guess. You mention it's sharp at the 3rd fret, but what about the 1st, 2nd, 4th, 5th, etc? The sharpness lessens as you move from the 7th to the 12th, but where does it go beyond the 12th? Do the problems repeat the same on all strings, or just on one or two courses?

Lot's of things can cause odd intonation problems. The action is high on the upper frets, which certainly doesn't help. Are you sure it's good at the nut - this is not always the simplest thing to learn how to gauge well. Have you tried new strings? Are problems isolated to certain frets, certain strings, or certain frequencies? A good diagnosis generally means considering a lot of different variables which interact with each other, and is not always the easiest thing to do if you're not fluent and familiar with what to look for.

Do you have a good shop near you? Where are you located?

[DerTiefster]

How about pitching it down a step, a half-step, something like that. (yes, I'm being overly cautious.) Then put a capo on fret 1 or otherwise hold fret 1 while doing the next step(s). If you tune to some pitch and re-position the bridge so the 13th fret is the octave (12 frets above the capo) and it then frets truly up and down the fret board, THEN you know the spacings of the frets are OK and that only the nut position is wrong. The nut might -look- ok and still be in the wrong position. Just my fiftieth of a dollar's worth.

[mandroid]

FWIW Re: metal files ... Vixen files from Nicholsen are made for shaping aluminum, they have rows of curved plane like cutting edges .
with a good gap between them, they make nice smooth cuts , ,

but I'd still use face up sandpaper ,, I did a modification of the Martin BP bridge using the sandpaper technique , and its nicer..

just gotta know when to stop.. :popcorn:

[Rob Gerety]

Seems like if string height it the culprit the problem would exist all over the fretboard - not just in the lower frets.

I wouldn't make any changes to it until you know what it causing the problem and until you are sure you are not going to return it.

I've got to say - it sounds pretty odd to me.

[DerTiefster]

If the nut is pretty high, then you get a large angle bend from nut to frets 1/2/3, lessening as you go up the fret board. The combination of short baseline and big (relatively) step height require (from Pythagoras) a larger increase in the string length to make it all the way from nut to fret to bridge. This increases the tension more than fretting at the 12th fret and that increased tension makes the pitch increase relatively more on fret one than on fret 12. Just geometry, but it requires a pretty excessive nut height.

[mandotrev]

You mention it's sharp at the 3rd fret, but what about the 1st, 2nd, 4th, 5th, etc?

It is most noticeable on an open G chord. My electronic tuner tells me it is also sharp on the first and second fret, as well, up to the 8th where it gets better and the 12th is flat.


Have you tried new strings?

Yes, it came with heavier gague flatwounds. I replaced them with much lighter gague Martins. No difference.


Do you have a good shop near you? Where are you located?

I'm in South Korea and finding a good luthier is very difficult



I wouldn't make any changes to it until you know what it causing the problem and until you are sure you are not going to return it.

I have corresponded with the seller in Germany. We have agreed that I should try sanding the bridge. She suggested a good lutihier. As I mentioned, that's difficult because of where I live.


If the nut is pretty high, then you get a large angle bend from nut to frets 1/2/3, lessening as you go up the fret board.

The nut height looks about average, I think.



How about pitching it down a step, a half-step, something like that. (yes, I'm being overly cautious.) Then put a capo on fret 1 or otherwise hold fret 1 while doing the next step(s). If you tune to some pitch and re-position the bridge so the 13th fret is the octave (12 frets above the capo) and it then frets truly up and down the fret board, THEN you know the spacings of the frets are OK and that only the nut position is wrong. The nut might -look- ok and still be in the wrong position. Just my fiftieth of a dollar's worth.

I'll try it.


Could be an improperly slotted fretboard, he said with an evil chuckle.

I guess it isn't impossible, but it's a Swedish company that was bought out by Martin. They have a pretty good reputation and Swedes aren't known for making blunders like that. They're pretty fastidious.

[Tavy]

It is most noticeable on an open G chord. My electronic tuner tells me it is also sharp on the first and second fret, as well, up to the 8th where it gets better and the 12th is flat.

That sounds typical of what happens when either the nut is in the wrong place (too far from the first fret), or when the strings aren't sitting in the slots right and are making contact behind the front edge. But as others have said, it's very hard to diagnose by forum!

John.

[mandotrev]

I wonder if mandolin nuts are difficult to replace? How do I get the old one off? Should I try filing the grooves so that I am certain that the strings are making contact right at the front edge? The nut is old and quite discolored.

[Mandophyte]

Mandotrev,

Have a look at this (http://www.frets.com/FRETSPages/Luthier/Technique/Setup/NewNut/newnut1.html).

FRETS.COM is your resource for most setup issues. If something isn't covered in the mandolin section look at the other instruments, there're all built in the same basic way.

[Rob Gerety]

You could measure the distance from the front edge of the nut to the middle of fret one - and one up the fret board at each fret to check the frets slot locations.

By the way - you said you got good intonation at 12 - was that with the harmonic or with the note fretted at 12? Check it fretted - set the bridge correctly - then move down fretting each note down the fretboard - that should tell you a lot. Maybe you have already done that?

[Dick Hutchings]

If you have a feeler gauge, you can take some measurements under the strings at the first fret. Also measure the distance from the nut to the first fret and to the 12th fret and post this info, I think these guys could help you more.

[DerTiefster]

Some instruments have a "zero fret" which sets the open vibrating string length. On those instruments the nut serves principally (solely?) to space the strings. The combination nut more commonly found does both functions. If the grooves of the nut are not angled up toward the frets properly, then the string may be anchored somewhere behind the face of the nut. If the nut face toward the fretboard is angled backward, then the distance from the nut face to the first fret can be larger than needed for proper intonation and the fret is effectively sharp. I suspect (but have not tried this) that one can take a vernier caliper and measure from front face of the nut to vaguely the center of the frets, successively, and check the relative spacings of the frets. This would test essentially what I suggested above with capo-ing the first fret and repositioning the bridge to get octaves on the 13th fret. If you get good intonation, then the frets are spaced relative to each other in a proper fashion and then -only- the nut is left as the Bad Boy.

You could also wedge a metal in front of the nut to anchor the strings a bit forward of it and then re-test for intonation (even one string at a time). If you get proper intonation on any single string and the frets are parallel to each other, then the rest have to work well enough. And as a bonus you know how far offset the nut is. An electronic tuner and a calculator can probably allow you to calculate how far offset the nut might be if you find the frequency error of the 1st fretted note, but doing it empirically also appears workable. If you find that it is not the bridge height that is causing your grief, you'll be happy not to have messed with it. But you might have to lower the strings to get the action you wish. One local luthier here slotted my bridge to lower the strings a mm or two as the most effective way to get the action height I wanted. You just have to pay attention.

[Chris Oliver]

I would hesitate to use a completely flat surface to sand the bridge bottom. Even tho it is a "flat top" mandolin I am sure that there is some induced arch to the top.

Not trying to hijack the thread, but... Jim what would induce an arch in a top with a floating bridge? Is it string tension across the top?
thanks,
chris

[NAS]

Here are some nice simple checks to start off.

Check the nut height. hold or capo the strings on the tail piece side of fret 2. use a 0.006" feeler gauge or if not available a piece of office paper, it should just fit between fret 1 and the string. If there is more much more than 0.006" gap the intonation will go bad on the first 5 or so frets. This method I was taught and it works for all Guitars, banjo, Mando, Bass I have setup. Ideally you need fret files but you can wing it with needle files and finally broaching the slot with a string offcut.

Measure the action at the 12th fret. shoot for 3/32" bass side 1/6" trebble (although my own instruments are set a hair above 1/16" bass, hair below 1/16" trebble but that suits my style). You can then shorten the bridge by twice the differnce between the measured height and the desired height,
i.e. if the measured bass string action was 1/8" (4/32) and we are aiming for 3/32" you would remove 2 x 1/32" = 1/16"

It works as it's simple geometry. we use this to set guitar saddles all the time and using vernier calipers to check each string height I get it right first time 90% of the time. so much quicker than taking off a shaving and re-checking repeatedly.

Hope this is some help.

Neil

[Tavy]

Not trying to hijack the thread, but... Jim what would induce an arch in a top with a floating bridge? Is it string tension across the top?
thanks,
chris

The bracing induces the arch - as well as resisting the push of the strings a slight arch helps to prevent the top becoming concave under changing atmospheric conditions.

John.

[Chris Oliver]

The bracing induces the arch - as well as resisting the push of the strings a slight arch helps to prevent the top becoming concave under changing atmospheric conditions.

John.

John, thanks, I wrongly assumed that 'induced' meant more arch than already created by bracing the top at x radius, i.e. some characteristic of the string tension induced the arch. I wondered if it was possible to have string tension so much greater than the downward pressure of the bridge that it caused the top to raise from its relaxed position to meet its equilibrium(instead of the opposite). This was not computing with me because it defied what I think I know about the top and the tension and pressure on it. See... my mind wanders.
I should have just read the comment in the context it was written.
chris

[mandotrev]

Tried the capo trick: I tuned down a half step and put a capo on the 1st fret, then checked the intonation up the freboard on all strings with an electronic tuner. The result was that it was sharp up to the eight or ninth fret and then went flat, then leveled out on the thirteenth fret, at the octave. The amount that it was sharp or flat was fairly uniform across all four courses. I emailed the seller and told her I didn't think it was the bridge or the nut.

Is it possible that if the instrument was stored in less than an ideal place for a long period that that the neck could have gotten out of whack? It appears straight. I can see no visual inconsistencies.

[Rob Gerety]

Bummer.

[DerTiefster]

I don't understand at all. I thought this would test whether the fret board spacings were OK with only the nut off-position.

If the nut alone were in the wrong place, then to get fret 1 to be sharp, the nut would be "too far" from the first fret (and all of the others, too). To get the octave at fret 12 you would have to space the bridge "too far" from fret 12 by the amount the nut is mis-positioned. Then all of the notes from fret 1 to fret 11 would be sharp, progressively coming into tune at 12, and frets 13 and up would get progressively flat from being too far from the bridge.

If this were the case, then to get fret 1 to be in tune with fret 13, you should have had to bring the bridge back toward the frets. You reported no bridge motion (maybe this was a simple omission). The reason I suggested pitching down a half step or full step was so that if the nut were really quite high, then capoing at fret 1 might increase the tension on the string and stretch it unnecessarily, work-hardening it. I said I might be over-cautious about that, and that was my reasoning which I didn't explain at the time.

With the assumption of good fret spacing and the nut not being so high as to cause string tension changes from fretting at 1, if you did not move the bridge or re-tune the string after capoing fret 1, then fret 13 should still be closely an octave up from the original pitch because you tuned the open string down a half step. That is consistent with one interpretation of what you said. In that same interpretation, the frets near 1 should still be sharp with respect to fret 13 because fret 1 is still sharp with respect to fret 13. And frets above 13 should still go progressively flat.

I -suspect- that you did not reposition the bridge for the test you made above, and did not re-tune the string to put fret 1 back on the original pitch (one of GDAE) because that's the way the report makes the most sense. If this is true, then you didn't really test the fret board for proper relative spacings. I am sorry if I have complicated things too much. I -think- that what I suggested makes physical sense.

Addendum: at the very least, if fret 1 were sharp from open and fret 12 on the money, then the spacing between 1 and 12 is too small with respect to the nut to bridge spaing. Then when re-tuning and re-intoning between frets 1 and 13 you should have to move the bridge closer to fret 1 to get them in tune. You didn't -say- that you did this, but maybe you did. It is an important step in doing the test I was intending to describe.

[Rob Gerety]

I think I understand this now - and I think you may be correct that the OP may not have followed the procedure you describe. Maybe he will report back?

[DerTiefster]

Yes. I tried to briefly outline the procedure one would use to treat fret 1 as a substitute zero fret, using fret 13 as the octave. With the nut in the correct position, there should be no bridge movement needed. But if only the nut is wrongly spaced, then using fret 1 as a zero fret should make everything else intone properly.

[mandotrev]

I am still working on getting this mandolin set up. One thing that might be important is that I have broken two high E strings on it. I don't recall ever breaking a mandolin string before. They seem to break much less than guitar strings in normal use. If I am breaking a lot of strings it would seem that I am getting too much tension. Is that a bridge issue? One string broke at around the 6th fret and the other broke right at the end, where it hooks behind the bridge. The first was from a set of J74 flatwounds (too heavy for me) and the second was from a set of light gague Martin Darcos. I'm not stringing them too high. I'm using ane electronic tuner.

[Tavy]

If you're breaking strings that usually indicates that they're binding in the nut (or bridge) slots - try getting some pencil lead (graphite) in the slots and the strings should move through the slots more easily - also check for any sharp edges that may have developed over time.

What happens BTW is that the part of the string between the tuner and the nut gets up to a much higher tension than the string between nut and bridge, so even though you haven't got the string up to pitch yet, none the less the part of the string between nut and tuner is at too high a tension and breaks. This also tends to cause the strings to go out of tune and or "ping" or slip. It also makes the intonation checks you've been doing much harder to do right since the string's pitch/tension is almost constantly changing.

Also confused as to what your problem might be, John.

[DerTiefster]

I noted the breakage report, but since one broke at the tailpiece hook (possibly an installation issue -- I've had breakage when I hooked the loop to one side and the loop wire scraped against the hook as tension rose and pulled it straight) and one at fret 6 (can't see anything but a nicked string doing that) I thought it was unlikely to be an issue with the instrument. Binding of the strings in the nut grooves (in my general experience) brings on breakage between nut and the tuner shaft. These are just my opinions, of course.

I'm still interested in the details of the full intonation test if mandotrev chooses to do it.

[Tavy]

I noted the breakage report, but since one broke at the tailpiece hook (possibly an installation issue -- I've had breakage when I hooked the loop to one side and the loop wire scraped against the hook as tension rose and pulled it straight) and one at fret 6 (can't see anything but a nicked string doing that) I thought it was unlikely to be an issue with the instrument.

Ah, I missed that bit.


Binding of the strings in the nut grooves (in my general experience) brings on breakage between nut and the tuner shaft. These are just my opinions, of course.

Mine too, and like you, if the nut binding is the issue then it should break between and nut and tuner IMO.


I'm still interested in the details of the full intonation test if mandotrev chooses to do it.

Me too.

Still perplexed yours, John.

[Phil Vinyard]

Get thee to a luthier. Was having intonation problems with my new Trinity College Octave Mando and I messed around quite a bit with bridge placement but never got it right. Yesterday I took it to Mass Street Music in Lawrence KS and Matt nailed the problem right away--action too high. Got some frets put in too high that he's got to deal with first, but then lowering the action should fix it all.

I had him go over my new Gibson after I'd had it a few months and he made a few small adjustments that I wouldn't have known to make,and the thing plays way easier. Well worth the few bucks I spent on it and the three-hour drive each way.

[David Newton]

Phil and the others suggesting taking it to a qualified person is right on. Mandolins have such a short scale, and very small adjustments go such a long way, and "rough" adjustments can take things off the scale in either direction very quickly. I don't think you can do a great deal of harm in trying it yourself, but the learning curve is pretty steep. Go read frets.com