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Post by funkykikuchiyo on Mar 24, 2023 10:45:57 GMT -5
A friend on the other side of the country has been frustrated with a Gretsch (Jet sort of thing, not sure which model) that goes flat after bends. He's taken it places and they've gone over it, but I'm not sure where he has taken it or how high their skill level is. He's been going crazy because he feels like everything has been checked multiple times. He's a retired engineer, and decided to duplicate it under a high power microscope on the nut to see if the string is moving when it goes flat. His conclusion is there is no movement there. The way it behaves sounds like a nut problem, and the fact that he has taken it places and it still acts up also sounds like the nut, since quick fixes often doing work there.
We're left in a weird position - is it possible for a string's tension on either side of the nut to change without a visual change in its location over the nut changing? It sounds unlikely to me, but not all changes in tension have visual changes, right? A glass bottle filled with lots of air doesn't bubble out, a table with a lot of weight on it technically compresses slightly, but probably not measurably. Sure, the glass bottle will eventually bust apart and if you put a block of wood in a hydraulic press it will visibly compress, but could a string move enough to change pitch 10-20 cents without a perceptible movement under a microscope?
If I could get my hands on it I could probably fix it quite easily, but this is all going on via text. For now it is an interesting thought experiment. Someone taped the bridge down and he tried blocking the bigsby with a clamp and a block of wood. He's done the same microscope thing at the bridge, but hasn't looked to see if the bridge is rocking. My guess is that isn't it since the whole guitar isn't changing tuning.
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Post by Auf Kiltre on Mar 24, 2023 13:44:50 GMT -5
Please post any discovery should you come across it, I'd be interested. My first thought was the Bigsby not returning to pitch after the added string tension from a string bend, but it sounds like that was addressed. A wonky neck relief issue?
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Post by ninworks on Mar 24, 2023 14:50:30 GMT -5
A close friend of mine has a Gretsch Tennesseean that was always going out of tune as well. There were 2 problems. The bridge was moving and the Bigsby was a piece of junk that would never return to the same location twice. First we glued some 400 grit wet/dry sandpaper to the contact points on the bridge and that helped but didn't fix it. Then we lubed the crap out of the pivot points on the Bigsby. That didn't help. We lubed the nut slots with Vaseline and graphite and that didn't help either. We took the spring out of the tailpiece and put a bolt with a nut on it to hold it in place and the problem went away. To this day I hate Bigsby tailpieces because of that. If he were using heavier strings the Bigsby might not have been a problem but with 009's it was a problem.
As far as the string not moving across the nut goes, it has to be moving or the pitch wouldn't change if uneven tension at the nut was the problem. As an engineer he should realize that. That's a pretty simple concept. I have a few Gibson guitars and every one of them will change the tuning ever so slightly after a big string bend. Primarily when doing it on the low E and G strings but it happens with all of them. All I have to do is tap the string on the back side of the nut and it goes back in tune. Either that or bang the crap out of the string(s) to equalize the tension on both sides of the nut. I have never tried to see if it was moving but I don't have what it takes to see a measurement that small. Why were locking nuts invented to fix tuning stability on guitars with a Floyd Rose tailpiece? To keep the strings from moving across the nut, why else. That actually works.
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Post by Pinetree on Mar 24, 2023 18:41:15 GMT -5
Ask your friend if it ever "pings" when tuning.
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DrKev
Wholenote
It's just a guitar, it's not rocket science.
Posts: 418
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Post by DrKev on Mar 25, 2023 6:29:02 GMT -5
Is it possible for a string's tension on either side of the nut to change without a visual change in its location over the nut changing? On one side *or* the other yes, and to do so requires the string to be bound in its slot. On *both* sides simultaneously, no. Rule of thumb for guitars with vibrato units - if all strings go out of tune the same direction, it's a bridge not returning to neutral position. Check all bearing/moving surfaces and lubricate. If a guitar has a locking nut, it could be loose and could also cause the same issue. If only one string goes out of tune and the rest are unchanged or slightly out the other direction, it's an individual string issue. Check all points on the guitar where the string makes contact and ensure no binding or sticking. If there are binding issues with multiple strings, you'll have two or more string going out of tune the same direction and others in the other direction, assume everything needs work. Resolve string issues first and then check the vibrato unit. |
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Post by Peegoo 🏁 on Mar 25, 2023 11:20:52 GMT -5
Odd indeed.
The only thing that remains is if the strings have been properly "stretched in." I'd have to assume they are because this is what you do when installing new strings.
What string brand? If this problem is occurring with a single brand, and if all the strings are from the same batch, I'd be trying something different. It would not be the first time the issue is defective strings.
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Post by Peegoo 🏁 on Mar 25, 2023 11:22:45 GMT -5
Is the guitar a screw-on neck Electromatic? Or a set-neck? It may be a loose neck issue.
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Post by funkykikuchiyo on Mar 25, 2023 11:58:09 GMT -5
Yeah, I get all of the usual tuning stuff. I just can't get my hands on the instrument and am trying to make sense of it with the data provided to me. My biggest query is if a lack of a detectible (not just theoretical, but observable) shift over the nut vetoes it from being a possibility, or if it is just a red herring. I've never bothered to look at a nut with a microscope, so I can't say for sure. I've certainly been surprised in ways like that before.
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Post by Auf Kiltre on Mar 25, 2023 12:29:03 GMT -5
N/M  |
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Post by funkykikuchiyo on Mar 25, 2023 12:48:24 GMT -5
Well, if you bend a string, you are pulling extra slack towards the playing area of the string and away from non-playing areas... more string mean less tension, less tension means lower pitch.
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Post by Auf Kiltre on Mar 25, 2023 13:18:18 GMT -5
Well, if you bend a string, you are pulling extra slack towards the playing area of the string and away from non-playing areas... more string mean less tension, less tension means lower pitch. Yes, this makes total sense and I don't know what I was thinking. Now excuse me while I go take a cognitive test lol. Auf/out. |
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Post by ninworks on Mar 25, 2023 21:13:50 GMT -5
Defective strings are a good possibility but if it is a nut or saddle binding issue, theory is one thing but basic mechanics is another. In order for the string to be binding in the nut or across a saddle, it can't bind if it's not moving, period. Whether it's observable or not is not even a thing. Even if it is just stretching the string it is still moving. However immeasurable or observable it is there has to be movement whether it is transverse or longitudinal. Otherwise locking nuts wouldn't work and they most certainly do. Just because the guy can't see it move doesn't mean it isn't. He just needs a better way to observe it. If there is more string on one side of the friction point or the other the string has to move in order for that to happen. It can't happen any other way.
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Post by Peegoo 🏁 on Mar 26, 2023 5:57:45 GMT -5
How about a practical experiment? Have your pal try the following. Use a toothpick to apply less than a drop of a PTFE-based light oil, e.g., Super Lube, to the top of each string in the nut slot. Slightly detune and retune each string five or six times; this moves the string through the nut slot and distributes the lube all the way around the string in the slot. There's no need to lift the string and physically apply the lube under the string. Wipe off any remaining oil with a paper towel. See if the problem persists.  |
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Wrnchbndr
Wholenote
Posts: 353
Formerly Known As: WRNCHBNDR
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Post by Wrnchbndr on Mar 28, 2023 11:47:42 GMT -5
I’ve encountered this exact problem many many times.
1. Tune the string up to exact pitch.
2. Wobble the trem.
3. Tune the string again if necessary but alway end by tuning “up” to pitch.
4. While watching the tuner, bend a fretted note up one full step and recheck the tune of the string — just record the result — how far off is it it?
5. Between the post of the tuning machine and the nut, press down on the string while watching the tuner enough to raise the pitch one full step.
If the pitch is now significantly sharper (typically 20 cents), the problem is the nut.
Don’t do this test if you haven’t noticed a problem.
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