Intonation

I apologize if this has been answered before but I'm not much on searching.

I have a Bushman concert Uke. I've had it for about five years and it's always been an excellent instrument. A couple of weeks ago I changed strings and installed new Martin strings. Now, even though I tune the open strings perfectly, the notes when fretted are too sharp. The chords sound horrible.

The strings are tight, stretched and stay in tune when open.
The C string is especially bad when I play a D note it's almost a D#.

The G and D chords sound especially bad.

Since this sounded fine before I changed strings I am wondering if it's something about the way the strings are not sitting properly.

Any help would be greatly appreciated.

Thanks in advance.

i had this happen to me once when i replaced the aquilas with another set of aquilas. i stretched the strings like i would do with guitar strings ( i was a newb and didnt know any better). as a result i messed up the A string which caused it to sound horrible and the intonation was way off. also, you could have just got a bad set of strings. try replacing the strings with another set of martins or any other sting of choice. every once in a while you come across a bad batch. now i dont stretch out my strings on my ukes like i do with guitar strings, and have not had any issues with intonation since.

Hello Flyingcursor

I agree with your assessment - fret a string at the third fret and look at the space between the top of the first fretwire and the bottom of the string. You should see a small space (thinkness of a regular xerox paper). If it is more like a thickness of a business card or a dime, something is weird. Now, to confirm, look closely at the nut slot. See if the nut groove is wide enough and the string is set to the bottom. It is possible that the nut slot is too narrow *or* the string is too thick.

Is this the first time you changed the strings? Do you remember what brand of strings you had on before?

Do you happen to have the package/label? I do wonder if you have a set for tenor ukulele. Since a tenor ukulele has a longer scale, a tenor string is a bit thicker and may not fit your nut.

I guess the easier thing is to get a new set of strings and try again......

Happy Picki
Chief

The new strings are probably a bit thicker than the old, and thus not seating all the way to the bottom of the slots in the nut. Another set of the same brand of strings is probably going to have the same problem.

Generally, when the slots are already the correct depth and just need to be widened a bit you can do it with a bit of 400-grit wet-and-dry paper folded over. Just be careful not to actually deepen the slots if the intonation was good with thinner strings.

From your description there are two possibilities:

1. Defective strings, with stretched spots in them. Your C string is the worst - swap it end for end. If the intonation problem moves around or goes away, it's a bad string.

More likely, because all strings give you problems,

2. The last point of contact for each string is towards the back of the nut, rather than at the front edge where it should be. This is either:

(a) strings not sitting down properly but being pinched at the back of the nut, where the slot is narrower, or

(b) these strings are narrower than the ones they replaced and sit fully down in the nut which was not cut properly - the base of the slot should slope from the fingerboard to the peghead so that the string breaks over the front edge.

Diagnosis method: Slacken C string, lift it out and clip it over the edge of the nut to keep it out of the way. Ditto for E string but place in C slot and retune it to E. Check intonation on that string. If pretty much right,you have problem (a) - widen nut slots with folded over sandpaper taking care not to deepen them. If still very sharp at lowerfrets you have problem (b) - you need to recut the bases of the nut slots so that they slope, but without making them any deeper at the front. Buy a set of welding tip cleaners and go very carefully.