JB-4L (Jazz Bass Left Handed)

[Keith Walters]

Used a tuner.
Fine for tuning the strings but problematic for getting the intonation right.
Used an amp with a built in tuner and kept going until the intonation was right.

OK. I know there's a lot of to-ing and fro-ing involved, but I didn't think you needed particularly accurate hearing. Actually my old-fashioned Korg tuner with the mechanical meter is quite a bit easier to use than the more recent digital types.
Of course, the best was the old Conn stroboscope with the spinning disc and the neon light modulated by the guitar signal. You could see everything at once on those.

[Keith Walters]

OK I've got the strings on.
Simon Barden is right; the bridge saddle wanted to go back a bit further than the spring would allow, but I just cut the spring in half; problem solved. (I know I'll probably be sent to H-E-Hockeystix by some purists here for doing that, but, as they say, any landing you can walk away from is a good one :-)
I did follow one set of instructions on here, and it just said to do what I did, make the saddle mid-position equidistant from the 12th fret.

But now I'm wondering precisely why the need to keep re-tuning the strings to set the intonation.
I can tune a guitar within about half a semitone by ear, and I can easily hear when fingering the 12th fret is the same pitch as the open string. I just did a few quick twang-twang adjust; twang-twang adjust etc cycles until they sounded the same, and when I re-tuned the strings using my guitar tuner and re-checked the intonation, it was still spot on.
I'm wondering why you can't just tune it once (either by ear or using a tuner) and do the intonation adjustments. Yes, it will go slightly out of tune every time you adjust the saddle, but does that really matter?

I haven't plugged it in to an amp yet, but it sounds pretty good "unplugged". It's all coming back, but my right hand is killing me....

[wazkelly]

The string thickness has a bearing on the required length to produced correct harmonic at 12th fret as this is supposed to be the mid point between nut and apex of that particular bridge saddle. Very basic high school wave theory physics and probably too hard to hear the difference unplugged but it should become more obvious once amped up. If not, running your signal through an electronic tuner will show up any tuning pitch anomalies.

If you get the chance to hear and play a poorly intonated axe played back to back with a properly set up one there should be a noticeable difference. Being a Bass it may be harder to tell due to lower frequencies.

[Simon Barden]

The amount it can go out of tune can be quite large. You are not just changing the distance between the nut and the saddle, but as you move the saddle, you are changing the angle of the string over the saddle, and this has the affect of also changing the string's tension. As you move the saddle towards the nut, the string length decreases but the tension also drops. As you move the saddle towards the nut, the string length increases but the tension also increases. You should have found that it was easier to move the saddles towards the nut than away from it, especially the closer the saddles got to the rear of the bridge. Some of this is the spring compression (though the spring isn't that stiff and is more of an anti-vibration device) but most is the increase in string tension. SO it is actually hard to do it just by ear, as the string length changes and the string tension changes partly cancel one another out, so you do really need to get the string back in tune again before checking 12th fret intonation.

However, if you have a good tuner that shows exactly how many cents off true you are, then you can tune proportionally e.g if the note is -6 cents down after a saddle adjustment, then if the 12th fret note is now also -6 cents down, then it should be intonated and bringing the string up to pitch, is then all that's required. But if the 12th fret note is -9 cents down, then it's still a bit flat, so the saddle needs to be moved forward. If I do it like this, then I normally bring the string fully up to pitch around every third attempt. And I always check again when it is at pitch.

[Simon Barden]

I did follow one set of instructions on here, and it just said to do what I did, make the saddle mid-position equidistant from the 12th fret.

Unfortunately, not every bit of advice given on this forum is 100% correct, or works in all situations. With the amount of postings that happen, it's hard to keep track of what everybody is writing and make a correction - though those are also easy to miss if it's a few posts after the original.

In some situations, especially if you have a bridge with a large amount of saddle travel available, setting them halfway can work and also allows for situation like Wazkelly found where by fitting a thicker string gauge to his bass, he had to adjust the G saddle very far forward, so that it was less than the nominal scale length. He had to replace the stock bridge with a longer Gotoh one to get the range of saddle adjustment needed. This was probably down to a quirk of the string construction, rather than a breakdown in the laws of physics, but shows that strange things can happen. Slight variations in string wrap tension or core wire diameter can make surprising differences even between the same gauge strings from the same manufacturer.

PBGs are starting a process of updating their build guides and making them fully inclusive, but it is going to take some time. So if you are unsure, keep asking the question until you are happy it's been answered correctly (hopefully with some reasoning behind it) and only then take action based on that answer - especially if it involves drilling holes and other actions that take a lot of fixing.

[Keith Walters]

I used the electronic tuner to check the intonation; all I'm saying is that I found no significant difference between when I did it by ear and when I used the tuner.
Anyway, another question:
The truss rod seems awfully hard to adjust and the neck is still slightly curved towards the strings in the middle of the scale. Is it meant to be that hard to turn or am I missing something? I don't want to break anything.

[Simon Barden]

If your ear and tuner give the same results, then just to it by ear. People's pitch differentiation skills vary. I was a volunteer in someone's university project where they were testing if classically trained musicians had better pitch differentiation than other people (a silly premise but there is often an ulterior motive to these tests that you aren't told about). My pitch differentiation (I was played 2 tones and asked whether the 2nd tone was lower, higher or the same as the first) turned out to be better than 3 cents (which is a fairly common electronic tuner accuracy) but a lot of people do have much lower pitch differentiation

The truss rod shouldn't be hard to turn unless it's either at the end of its travel or there's some swarf caught in the threads.

When you say that the neck is 'still slightly curved towards the strings in the middle of the scale', can you just confirm that you are saying that the neck has a slight upward/convex bow to it, rather than the slight downward /concave bow in the middle that you would expect?

If so, the truss rod needs to be loosened (rotated anti-clockwise). From loose, tightening it first reduces concave bow, then makes the neck flat and then introduces a convex bow. See the diagram below which should hopefully remove any terminology misunderstandings.



So if your neck is slightly convex, you need to loosen off the truss rod. Depending on how well levelled the frets are, you can get away with anything from flat to quite concave (never convex), but the best overall action without buzzing is normally found with a very slight concave bow in the neck.

Loosening off the truss rod nut won't be risky, even if it does feel a bit stiff. Sometimes a squirt of WD40 or a drop of penetrating oil down the truss rod hole will help make things move easier (WD40 is less likely to leave a stain, thpigh the oil may be more effective). If still stiff after several turns, it's probably worth removing the truss rod nut completely, cleaning inside it and the end of the truss rod threads, adding a drop of oil and hopefully it will be a lot smoother when you put it back on.

If you currently have a concave bow, and the rod won't go any tighter when turned clockwise, then it may have reached the end of the screw thread - or there may be swarf or dirt in there. So it's still worth undoing the nut, then cleaning the nut and the thread, putting a drop of oil in and see where that gets you.

If that still doesn't work, loosen the truss rod right off, turn the neck upside down, support the neck at both ends than hang some weights from the middle of the neck for a day or so to try and encourage the neck to flatten. This can work, so it is worth trying.

[Keith Walters]

When you say that the neck is 'still slightly curved towards the strings in the middle of the scale', can you just confirm that you are saying that the neck has a slight upward/convex bow to it, rather than the slight downward /concave bow in the middle that you would expect?

Yes it has that. It appears the truss rod works the opposite way to what I thought. However it is still tight in either direction. I'll try what you said.

Another question; I only just noticed that the volume control closest to the strings (ie the one controlling the pickup closest to the nut) is wired back-to-front compared to the other one. So if you turn it fully clockwise (which you would expect to give maximum volume) you get zero volume from that pickup. Is that some peculiarity copied from the original Fender design, or just a mistake in the factory?
By the way, I notice that Michael "Flea" Balzary of the Red Hot Chili Peppers uses the same model Fender Jazz Bass that mine was "inspired" by, actually an extremely rare pink painted early 60s model. It looks like it's had a hard life and a lot of the paint has been worn/chipped away, but not only is Flea not interested in getting it refurbished, Fender now sell a "Flea" model Jazz Bass, complete with all the battered paintwork faithfully replicated!

[Simon Barden]

Your neck problem seems solvable (which is good), but if the truss rod nut is stiff both ways, it is worth taking it off, cleaning and oiling it.

The volume control knob issue is strange, and moves into an area where I've had no experience; left-handed guitars. Both volume knobs should turn the same way, but after a web search, there is debate about whether this is ideally clockwise (as on a right-handed guitar), or anti-clockwise (which would seem more natural to me but involves using anti-log pots for at least the volumes, and either knobs with no numbers on or specialised reverse numbered knobs).

What are you used to, Keith?

Can you take a picture of the rear of the control plate showing the wiring? If the wiring of both pots looks the same, then it's possible the factory have fitted one log and one anti-log pot. If they've simply crossed over the wiring on one pot, it's a simple matter to fix (if you have any basic skill with a soldering iron). If it's the same wiring and you've got mixed pots, then you'll either need to return the plate to PBG for a replacement, or you could simply replace the pots (I'd get some upgraded ones whilst you're at it) and re-wire the control plate yourself.

Either way I'd drop Adam an email, as a pre-wired control plate should be 100% correct and he needs to let the factory know.

[Keith Walters]

Both my other left-handed guitars use conventional pot wiring: ie, clockwise makes it louder.

The wiring on the JB is not standard pot wiring anyway.
With a normal volume control, the signal source (ie pickup) is wired across the two outermost pins of the pot, with the shield connected to the "anticlockwise" pin. (Anticlockwise looking at the knob side). The amplifier connection is taken from the centre (wiper) pin, with its shield also soldered to the anticlockwise pin.

In my Bass, the pickups are wired with the signal ("active") wires going to the wipers of the pots; on the pot for the bridge pickup the shield wire goes to the "anticlockwise"pin, and the signal is taken from the clockwise pin.
On the pot for the other pickup the shield wire goes to the clockwise pin, and the signal is taken from the "anticlockwise" pin.



I know the reason for connecting the active signal wires to the wipers; because there's no selector switch, if they were wired in the conventional way, turning down the volume on one would also turn down the volume on the other.

I really just need to know if swapping round the output and shield pins was intentional or not. I can easily re-wire it.