Jazzmaster/Jaguar Trem Lock and Operation
Earlier this week, I hit on a problem that I've seen a couple of times with the trem tailpiece of a Jazzmaster (same applies to the Jaguar). I had to repair it and, afterwards set up the instrument. While the problem is not the most common, I've seen it enough that this might be helpful to someone (and I hope it'll be interesting to the rest of you). 🙂
As we've talked about before, most tremolo (yes, I'm using 'tremolo' when I know it's 'vibrato'—it's a done deal, remember) bridges balance the string tension against an opposite spring tension. On the Jazzmaster and Jaguar, the string anchor down the back of a sort of right angle bracket that pivots. Strings pull one way and the spring you see beneath pushes it back.
Let's include a gif at this point so we can see a little movement here and get an idea of the pivoting that's occurring.
Where to balance or 'float' this particular tailpiece isn't always clear and sometimes you'll go a little higher or a little lower but, usually, the tailpiece is floated at exactly the point where the trem lock slider 'holds' the tailpiece base. If we consider this the neutral point, when the slider is engaged, the trem becomes dive-only and no upward travel is possible. See below.
There's another (arguably more useful) function for the trem lock. This stop slider is actually a brilliantly clever and stupidly simple little device. Usually, if you break a string on a trem-equipped guitar, the imbalance in string to spring tension pulls all of the remaining strings out of tune. If this trem is properly set up, the trem lock slider can provide a means to set everything back to its neutral point. All other strings should now be back in tune. More or less but it actually works pretty well.
Or, I should say, it usually works well. It’s a little more difficult for it to do its job if the slider does not move back far enough to actually engage with the pivoting tremolo base. That’s what happened on the guitar I've been working on. The slots not long enough. At the extent of its travel, the trem lock just barely touched the edge of the baseplate and didn’t move back far enough that the plate could sit against it.
The fix is reasonably straightforward although it's a minor pain. Disassemble the unit and lengthen the slider slot to allow it more rearward travel. Disassembly is just a few screws—back out the spring tension screw and remove the spring. Then back out the screws holding the pivot plate (on which the trem pivots). The trem lock slider itself is usually a chromed disc on top that's been screwed and epoxied to a brass cylinder below. It's possible to break the epoxy bond but, if as long as you're careful, it shouldn't be necessary.
Use a needle file to lengthen the slider slot towards the rear. Take some care here. You want to keep things straight and even (and looking good). You also want to avoid filing the slider so make sure it's taped up out of your way. Don't use too rough a file to avoid chipping the metal plating. Luckily, you should only need a millimetre or two here. Reassemble to check progress until the slider sits under the edge of the trem plate by maybe that 1–2mm (3–5/64") or so. It doesn't need much. See below.
Incidentally, while the bridge is disassembled, it's not a bad idea to clean up the bearing surfaces. The bearing edges of the pivot plate in particular are typically pretty rough. Use some 220-grit sandpaper backed on something flat to clean off any burr or roughness from when they were cut. It all helps the system return to pitch later on.
And, once everything is back together, you need to set it up so the tailpiece is balanced in exactly the right spot for the trem lock to engage. It needs to be set so that you can push the slider all the way back and it jussssst sneaks in between the tremolo plate and the base. When it's just right, it will prevent any upward pull on the whammy bar but will not push the tailpiece out of position when engaging.
If the spring's too tight, the slider will hit the edge of the trem plate before engaging and you won't be able to push it all the way back without dumping the trem down. If the springs's too loose, the slider will move all the way back but there will be a gap between it and the trem plate that allows upward pulls.
It can be a delicate back and forth balancing act to get it just right but, luckily there's a shortcut.
Tighten up the spring tension screw a little and tune to pitch.
Dump the whammy bar and slide back the trem lock back. When you release the whammy, the trem should come to rest on the slider and your guitar will be out of tune.
Retune the guitar at this point.
Now, disengage the trem lock and you'll find your strings will pull sharp.
Loosen the spring tension screw until tuning returns to pitch. You should now be floating in pretty much the right place although you might need a little finessing of the tension/tuning equation.
You're right when completely engaging the trem lock doesn't alter the tuning and it prevents any upward pulls on the whammy.
This article written by Gerry Hayes and first published at hazeguitars.com
