Zero Fret and Intonation

I have this cheap plastic-fretboard Harmony soprano that needs a little TLC. The frets, fretboard, and nut are all one piece of plastic, screwed into the neck at the 1st, 5th, and just past the 12th fret. It has a nice sound to it, but the intonation is awful at the first few frets. The action is pretty high, which could be the problem, but I'm also a little concerned about the zero fret. The strings seem to bend at the zero fret whenever I play chords on the lower frets, thus raising the pitch just enough to throw the chord noticeably out of tune. I've attached a picture of the problem area, if it makes a difference.



Could the zero fret be the problem? If so, how should I go about lowering the action on this uke? Any help will be greatly appreciated.

haole said:

Could the zero fret be the problem? If so, how should I go about lowering the action on this uke? Any help will be greatly appreciated.

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Not sure about the zero fret being the problem - its usually there for a reason. Measure your scale from the zero fret to the 12th, and 12th to the bridge. They should be the same, and add up to your total scale length. Of course, some builders add in a little compensation on the bridge end by extending the scale a tad.

Action, as stated, won't fix your intonation, but I'm guessing this is something you want to do anyway. The answer is, depends. Is it high at the nut, or at the bridge. Frank Ford's site can help.

Before you do anything, one question - what kind of strings?

-Aaron

The scale length is an even 13", and the distance from the zero to 12th fret and the 12th fret to bridge are within a millimeter. I doubt Harmony was looking for good intonation when they designed the wooden one-piece bridge/saddle that's on here now.

The strings rest across the zero fret and are pushed up slightly, raising the action significantly. It's on the high side at the bridge too.

D'Addario J65s are on here right now. They're admittedly on the heavy side for this uke. Should I try some thinner strings to see if the problem improves?

haole said:

The strings rest across the zero fret and are pushed up slightly, raising the action significantly. It's on the high side at the bridge too.

D'Addario J65s are on here right now. They're admittedly on the heavy side for this uke. Should I try some thinner strings to see if the problem improves?

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Properly slotting the nut shouldn't be too hard if the action is too high at the nut. Again, instructions on Frank's site. I wouldn't feel to comfortable adjusting the action on a one piece bridge/saddle, but if you have to, you have to. Just be sure to adjust the action at the nut, before you touch the bridge. If your action is that high, yes, it can affect intonation. In your case, seems that it may be a contributing factor.

Personally, I don't really care for D'Addario `ukulele strings. Their Pro Artes, different story altogether.

Try some thinner strings if your intonation currently goes sharp. Worth may be a good idea if that's the direction you need to go.

Hope this helps - Aaron

Sorry, let me try this again regarding action at the nut. You have a Zero fret, hello Aaron, anyone home? First, the Zero fret is supposed to be higher than the rest of the frets. Adjusting the action at the nut would require taking the Zero fret down to where you want it. To summarize Frank, fret the third, and check the spacing under the 1st fret. Guideline is a business card, but I do mine a little closer with higher tension strings. THEN you set the action at the bridge. And let me rephrase since it seems the action is THAT high - yes, high action CAN cause intonation problems (I've not seen this happen too often though, its usually the strings). Sorry for the confusion. I hope this helps.

Thanks for your help! Wasn't sure if filing down the zero fret was okay or not. I took the zero fret down a hair, and checked out some of Frank's setup FAQs to get the action about where I wanted it. Still not crazy about this bridge, but the action at the nut/zero fret is better, and the intonation between the first and third fret has improved enough.

The increased string tension from stringing it up with Worth Browns might have had something to do with it as well. Not only that, but the sound has improved.