spacecowboy Posted February 8, 2020 Share Posted February 8, 2020 So got a bit of a problematic bass on my bench at the moment. I knew when my friend gave me it to setup it would be a challenge but i'm stumped with this one and need some advice. I think my friend would be fine with me saying that this bass came in very worse for wear, it's been played and gigged hard and had been left for some time in it's case, a few years i believe. The metal had all rusted and the neck looked completely banana'd, without a lie the gap between the underside of the E string to the fretboard was 12mm. So the things that have gone well so far; Its a Mex Jazz Bass, with a swapped out Bad donkey Bridge. Took the neck off the bass, gave the truss rod a few tweaks to leave over night, came back to it and the neck was completely straight, not a single gap on my straight edge. Excellent. Levelled all the frets as they were very uneven and beaten up, crowned them, got them looking super lovely, checked the fretboard wood again, completely straight. No rocking on any frets. Excellent!. Put the neck back on the bass, put the old strings back on to do some more trussrod tweaks before new strings were put on... 12mm gap is back... instantly... so the tension and pull of the strings is completely pulling the neck out of shape and causing some serious upbow. I completely loosen off the truss rod, lubricate the nut and over the course of a week start to turn it a quarter turn to tighten it up again all under tuned up string tension, the truss rod is now at the point where I don't want to turn it anymore, it's getting stiff but there has been ZERO movement in the neck, not even a mm over the course of week. In comparison a recent Marcus Miller bass setup saw all neck problems resolved overnight with no fuss. I have taken the neck off the bass again, tweaked it to be completely straight, put in on the bass again, instant up bow, no amount of tweaking will resolve it. I'm stumped. Does anyone have any ideas at all? Photos below to help out. Cheers, Quote Link to comment Share on other sites More sharing options...
Bigguy2017 Posted February 8, 2020 Share Posted February 8, 2020 Assuming (!) the truss rod was correctly installed from the off, and now it's doing nowt', something must have let go somewhere. Truss rod come loose at body end, truss rod snapped or nut run out of thread? What is the adjustable end like - allen or hex nut? Try some washers under the nut? 1 Quote Link to comment Share on other sites More sharing options...
spacecowboy Posted February 9, 2020 Author Share Posted February 9, 2020 Hi, It's an allen key, imperial 3/16th I believe. Feels like it moves fine, but it does nothing, but does get tight, that's why I'm a little confused with it. No idea if someone else has ever had a play with it any other time. Cheers, Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted February 10, 2020 Share Posted February 10, 2020 Hi It's difficult to see from the photo, but is it a bow, or is it just a very high action, or a bit of both? Which fret is it at 12mm and what is the gap at, say, the 21st fret with the strings tensioned up? In terms of the 'standard' measurement of neck relief, with strings held down to the frets at the 1st and the 18th frets, what is the gap at the 7th fret? When the neck is off the bass, is it possible to induce any back-bow at all? If not, then it sounds like the rod is out of adjustment or faulty, or that the neck has 'relaxed' over time into a bow that is too large for the trussrod to correct. With the strings off and the trussrod loosened, what was the gap in the middle of the fretboard? If you can get some back bow with the strings un-tensioned, it's worth trying starting off like that and then adding the string tension. If, with the strings off there is decent effect from the trussrod, but nevertheless a remaining substantial gap in the middle of the fretboard with the trussrod fully loosened, then you are probably into a defret, relevel and re-fret (I had to do one recently with exactly that issue) or, worst case, consider a replacement neck. Clearly, if the bow itself is controllable with the truss rod, but the overall action is still very high, then a shim at the rear of the neck pocket will get it back to normal adjustment range. Quote Link to comment Share on other sites More sharing options...
Bassassin Posted February 15, 2020 Share Posted February 15, 2020 Sounds to me like the rod's having no actual effect. When you're tightening it, are you manually flexing the neck back to de-tension the rod? You should be able to tell if it's reaching the limit of its adjustability before it can affect neck curvature. If that's what it is, a couple of washers under the allen nut should give you a few more turns and hopefully restore function. Quote Link to comment Share on other sites More sharing options...
spacecowboy Posted February 17, 2020 Author Share Posted February 17, 2020 On 10/02/2020 at 16:21, Andyjr1515 said: Hi It's difficult to see from the photo, but is it a bow, or is it just a very high action, or a bit of both? Which fret is it at 12mm and what is the gap at, say, the 21st fret with the strings tensioned up? In terms of the 'standard' measurement of neck relief, with strings held down to the frets at the 1st and the 18th frets, what is the gap at the 7th fret? When the neck is off the bass, is it possible to induce any back-bow at all? If not, then it sounds like the rod is out of adjustment or faulty, or that the neck has 'relaxed' over time into a bow that is too large for the trussrod to correct. With the strings off and the trussrod loosened, what was the gap in the middle of the fretboard? If you can get some back bow with the strings un-tensioned, it's worth trying starting off like that and then adding the string tension. If, with the strings off there is decent effect from the trussrod, but nevertheless a remaining substantial gap in the middle of the fretboard with the trussrod fully loosened, then you are probably into a defret, relevel and re-fret (I had to do one recently with exactly that issue) or, worst case, consider a replacement neck. Clearly, if the bow itself is controllable with the truss rod, but the overall action is still very high, then a shim at the rear of the neck pocket will get it back to normal adjustment range. Hi Andyjr1515, Thanks for the reply, It's definitely a bit of both, the action is high, not so much at the nut end but the bridge end it's very high, the saddles on the bridge are bottomed out but I don't want to file the saddle until the neck is straight. The 12 - 10mm is at the 12th fret, so the fretboard at that point is almost parallel to the string, before it then rises up at both ends. When you do the string straight edge technique you mention the string doesn't seem to be too high off the fret, I haven't had my calipers on it, but it looks to be 3mm ish. At the 21st fret it's very high again, possibly around the 8-10mm mark, but I can get the calipers on the bass tonight and give you proper measurements. I'll do the things you've suggested and see if I can induce the backbow and then see what I get when the neck is back on the bass. Really appreciate the comments and suggestions. Thanks, Quote Link to comment Share on other sites More sharing options...
spacecowboy Posted February 17, 2020 Author Share Posted February 17, 2020 On 15/02/2020 at 16:13, Bassassin said: Sounds to me like the rod's having no actual effect. When you're tightening it, are you manually flexing the neck back to de-tension the rod? You should be able to tell if it's reaching the limit of its adjustability before it can affect neck curvature. If that's what it is, a couple of washers under the allen nut should give you a few more turns and hopefully restore function. Hi Bassassin, I haven't applied any hand force when tightening no, I'm a little worried to do that with a friends bass . What I do have however is some good vices on my work bench that I have been tempted to put the neck in and "squash down" however as this isn't my bass I don't want to do anything drastic if I can help it! I'll give all the above a go and see what we can do. I'm feeling that a new neck could be an instant fix, but a mixture of the above might remedy it all. Cheers, Quote Link to comment Share on other sites More sharing options...
Stub Mandrel Posted February 18, 2020 Share Posted February 18, 2020 OK. I have a squier Jazz Bass that has, three times, been adjusted only to have a bow return to the neck. I had to add a spacer to the adjuster nut. It appears the anchor at the fat end of the neck was shifting. As it's otherwise gorgeous, I wanted to save it, so a hideous bodge formed in my mind, but it meant finding the anchor point. I thought I might be able to do this with magnets? Anyway loosened truss rod and removed strings. Took of neck and - LO! the anchor is covered by a round plug and there's a gap between the end of the skunk stripe and the plug so I can see the truss rod! No need for magnets, divining or probing with a small drill, straight to the bodge! I fed the anchor point with about 1cc of quality Loctite superglue through the hole, as much as I could get in and allowed it to soak in and hopefully strengthen the wood around the anchor point. This was two weeks ago, the bass has held its adjustment through at least four rehearsals and I even gigged it last Saturday! 1 Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted February 18, 2020 Share Posted February 18, 2020 Great info, @Stub Mandrel Quote Link to comment Share on other sites More sharing options...
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