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Post by itm on Aug 7, 2023 17:43:41 GMT
I have an SC-550 with a strange intonation issue which affects the top 3 (unwound) strings at frets 20 & 21 only. The pitch at fret 20 is a whole semitone sharp, and the pitch at fret 21 is exactly the same as at fret 20 (i.e. there is no change in pitch when moving from fret 20 to 21). This applies only to the top 3 strings (G,B,E), all of which are unwound. The bottom 3 strings are fine. The frets are all in very condition, with very little wear. I've tried adjusting the intonation of the top 3 strings, turning a screwdriver ant-clockwise to move the bridge saddles further away from the neck, but it has made no difference. Any idea what the problem might be, and how to fix it?
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608 posts
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Post by oghkhood on Aug 7, 2023 18:00:45 GMT
In a bulk !
- worn frets ? - strings in not so good condition ? ( and I see on the piture that they are not clean ) => wich was the pb, if the strings are not brand new, you must change them to get a confirmation of the pb - pick ups too high ? - intonation not as accurate as you think it is - neck set up ? staight in 3d ? truss rod fine ?
There can be a lot of reasons, but let me insist that you have to check it with new strings, preferably of a renown brand, and set up the intonation with new strings, mandatory
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advb
Harley Benton Expert
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Post by advb on Aug 7, 2023 22:28:45 GMT
oghkhood is right that old strings can cause all sorts of intonation problems. However, I'm not sure that intonation is the issue here. If you fret a string at any fret and look carefully from the side along the next fret, you should see some clearance. It sounds like fret 21 is too high (or fret 20 is too low) and the string is not clearing fret 21 at all when you fret at fret 20. So, in other words, when you are fretting fret 20 it is also touching fret 21, so the notes are the same. DefJef beat me too it! It is possible that fret 21 was not seated properly all the way across when it was fitted and it may only be high on the upper strings side of the fretboard. If you don't have a fret rocker, you can use anything with a flat edge - like a credit card - to check if the fret is actually high. Place it on frets 20, 21 and 22 next to the G, B and E strings in turn. If fret 21 is high, the flat edge should rock slightly against fret 20 and 22. If the fret is too high under the upper strings, a potential fix is to tap it down with with soft faced nylon or brass hammer. (Nylon or brass are softer than the fret so shouldn't dent or damage it.) Obviously, you have to remove the strings or at least slacken them and move them out of the way before tapping down the fret. If it is still high afterwards, the fret might have to be slightly filed down and re-crowned.
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Post by itm on Aug 8, 2023 11:10:06 GMT
Thanks for the feedback - that sounds logical, but to my untrained eye it looks as if fret 20 is maybe too low, rather than fret 21 being too high? - the photo shows frets 19/20/21/22 (from right to left).
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advb
Harley Benton Expert
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Post by advb on Aug 11, 2023 22:35:33 GMT
Hi itm . Sorry I haven't replied earlier but I've been away for a few days. Its not really easy to tell from the image whether fret 20 is too low rather than fret 21 being too high - we are talking about very small measurements - but it is quite possible. Most internet resources and tutorials concentrate on high frets, probably because its relatively straightforward to sort out a single rogue high fret. Low frets require more work, as potentially all its neighbours have to be levelled down to its height. At least your problem is at the very end of the neck, so you might be able to fix it by levelling down frets 21 and 22. After all, if the guitar plays nicely at your preferred action over the rest of the neck, a full fret level and crown wouldn't gain you much but would lose fret material on the good bits of the neck! This all assumes that the neck relief is correct: if you have too much relief, when you lower the bridge to get the correct action in the middle of the neck, the string clearance on the upper frets can be insufficient to stop buzz or choking out. Try checking the string height from 12th fret upwards. There should be a steady increase as you move further up the neck. I got caught out by this. I'd switched up from .9s to .10s on my HB35 at the last string change but hadn't got around to adjusting the relief. Because of the extra string tension, the relief was much too much and I was getting some choking on the high frets. I measured the string height at the 12th fret and then upwards. The height increased up to the 15th fret (as you would expect) but then levelled out as the influence of the truss rod finished. By the last (22nd) fret the height was the same as the 12th fret! Obviously, a high (or low) fret won't get fixed by changing the neck relief but the correct relief might reduce the problem to a more acceptable level.
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