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yu108056@yorku.caThis is a 'how to' that I found on the internet. It sounds pretty informative to me.
I was recently asked how to adjust a bass, so I thought that I would pass this on to the whole list. This is the procedure that I have gone through on all of my basses. Feel gree to adjust my method to suit your own preferences. The important thing is to get one system down and stick to it so that you can duplicate what you have done. Of course, everyone likes his or her bass setup in a different way, so the measurements that I use may not be appropriate for your bass and/or your playing style. Also, your bass may or may not have all of the adjustments that I am talking about. For instance, not all basses have a neck tilt adjustment screws. For that matter, some basses don't have bolt on necks anyway. Expect to have to adjust your bass every time you change string sizes, and also expect that your bass will change with changes in the weather, unless it is made of graphite, and then I don't want to hear about it, you lucky dog!
I'll start from scratch here, but you can start at any point in the procedure. Read the whole thing first before you actually try any of it. You may want to thoroughly clean your bass if you have the strings off of it. I like to pay extra attention to the fretboard right next to the frets. (I couldn't ever be like James Jamerson and not ever clean my bass, but I do admire his playing!) I have even taken all of my basses completely apart at least once. OK, so I'm an obsessive, compulsive, anal retentive kind of guy, what can I say? It was there, and I had to do it.
To adjust your own trust rod, neck tilt, bridge and intonation, get a couple tools ready. My method requires a capo, a feeler gauge set, a machinists 6" steel ruler, a couple of allen wrenches and a couple screwdrivers. I bought a cheap capo for a couple bucks - don't bother with the fancy $18 ones. I had the ruler, wrenches and screwdrivers because I used to be a machinist.
First, loosen up the screws that hold the neck on. Then use the allen wrench to back off the neck tilt adjustment screw that is accessed from the hole in the plate the neck screws go through (or at the other end of the neck). After you have loosened the tilt screw, re-tighten the neck screws. The tilt screw should still completely slack after the others are tight. Don't worry, we'll come back to it later.
Next, string up the bass with the set of strings that you will be using. Try to only have about three turns of the string on each tuning peg. Tune up your bass to the tuning you will be using. If the pickups look like they are to close to the strings, use a screwdriver to lower them. Now, put the capo on the first fret. We will be using the strings as a straightedge. To get as accurate a measurement as possible, hold the bass in the same position as you play it. Gravity really can change the relief on these big thangs! Hold down the string at the last fret (for me, the 22nd) and measure the distance between the string and the fret at the half-way point on the fingerboard (for me, the 8th). This will tell you how much relief the neck has. I like to see about .014" between the string and the fret. I use a set of flatt feeler gauges to tell. Choose one and see if you can fit it in between the string and the fret without lifting the string. If the distance is more than .014", then you have to tighten the truss rod. Only tighten or loosen the trust rod about an eighth of a turn at a time, no more. If you have an old P-bass (I have one), you'll have to actually remove the neck from the body to do this properly.
Once the relief is set, take off the capo and pick up the machinists ruler. Hold the ruler on the last fret of the neck (closest to the bridge) and measure the distance between the string and the fret. This tells you how high your action is. I like to see 5/32" on my low B and 4/32" on my G string. If the distance is more than 5/32" then you have to lower the saddles on the bridge. If the distance is less than 5/32" then you have to raise the saddles on the bridge. Use the correct allen wrench and sdjust the screws on each saddle evenly. I usually turn each screw 1/2 turn and recheck the measurements. The most important thing to accomplish here is to make the strings be an equal height off the neck. Don't adjust the saddles so that they are bottomed out on the face of the bridge. If they won't go down far enough, then adjust them to a reasonable point and make all the strings as even as you can, matching the lowest one. (For me th lowest one is always the G).
Once the strings are all even, decide if they are stil too high for your style of playing. If they are too high, then the neck tilt adjustment screw need to be tightened. Loosen the neck screws, and tighten the neck tilt screw a little bit. Same as the truss rod nut, 1/8 turn is a good starting point. Now tighten the neck screws again and recheck the measurement. Repeat this until the height of the strings is to your liking. At this point, you should be comfortable with the way this whole procedure to get to a happy medium. Don't forget, the lower the action and the less relief the neck has, the more possibility there is for fret noise. On the other hand, too much relief and too high an action can be hard to play and, in excess, can cause your neck to warp, especially if you use heavy strings. If you have a bass without an adjustment screw, like my old P-bass, then you can stick a little piece of something under the end of the neck before you bolt it on to the body. A piece of match book cover is actually quite good.
Whoa, we're not done yet. Two more things. Adjust your pickups so that they are at a point where they won't get sanded down from contact with the strings, yet aren't so far away that they lose volume. Be careful though, that you don't put the pickups so close that the magnets in them pull on the strings, damping out the sustain. The thicker your strings are, the closer the pickups can be because of the higher tension that thick strings have. My Lace Sencsors are nice! No magnet pull, so I just stick them up as close as I can without having them rub.
Now, last, but certainly not least is to adjust the intonation. This is easiest with one of the electronic tuners. Make sure that the open strings are in tune. Then check the tuning at the twelfth fret. If the twelfth fret is sharp, the the saddle needs to be adjusted away from the nut, so that the string is longer. If the twelfth fret is flat, then the saddle needs to be adjusted toward the nut, so that the string is shorter. This is done by adjusting the long screw that holds the saddle against the pull of the string. Again, like the truss rod, and the neck tilt, a little tightening or loosening goes a long way. You will have to retune each string after every adjustment and then check the tuning at the twelfth fret again. The biggest thing that affects intonation is the height of the string off the neck (the "action"). Every time you adjust the string height, you should recheck the intonation.
Well, now you have it. Keep records of the measurements and play your bass fo a while and see if there is something you want to change. If you want to change it, why not, GO FOR IT! Only you really know how you want to change it, so why not do it yourself. As long as you don't try major surgery on your instrument, it is very hard to cause serious damage. The most important thing is to keep your truss rod tightened enough that it prevents warping. Don't ever leave the truss rod nut completely loosened! You should pretty much follow the order of the adjustments that I followed, because the subsequent ones depend upon the previous ones to work right. BTW, I have to give credit to Jack Schwarz, the Fender factory tech. I learned all this stuff from him when he was here in Tucson giving one of his tune up clinics.
For a more in depth study of setups and guitar/bass repair, I have to recommend Dan Erlewine's book, "The Guitar Player Repair Guide".
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