Lopsided Jazzmaster Vibrato

[lemming]

1965 Jazzmaster -- pressing the vibrato arm only activates 1/2 of the unit (the half on the side of the arm itself). It's almost like the other side is stuck on something, but that doesn't seem to be the case. Adjusting the spring doesn't help. It is possible to force the other half to move, like by wedging a flat screwdriver blade under it and prying. There's not really a lot of resistance when you do this , either. It just doesn't move by using the arm. This ain't right, right?

[timtam]

Assuming the lock is off, and none of the plates are bent or loose, the main trem plate should rotate freely and evenly along all of the knife edge contact at the rear (Fig 4a in Leo's patent below). The possible impediments to that are the gap in the plate through which it passes outside the guitar to anchor the strings (which it should clear), and the collet on the edges of the hole through which it passes.


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[LizardKing]

Maybe the spring is bad, they will sit crooked like that when messed up
and considering the age that might be it too if the rest of the tremolo checks out fine.

[Todd Connelly]

Well, unless you have it mounted in the guitar with the strings on and tuned more or less to pitch it's not going to behave in any way normal right? It needs the tension of the strings to force the trem plate against the knife edge which would then keep it square. In the scenario your picture shows it is behaving exactly as I would expect.

Cheers..................Todd

[lemming]

Thanks much for the responses!

The possible impediments to that are the gap in the plate through which it passes outside the guitar to anchor the strings (which it should clear)

This is great! Upon further inspection, it does seem to be rubbing against the sides of the gap somewhat. The "front" side of the unit that is opposite the collet doesn't move at all when you press the arm. The "collet side" moves fine, but the other side stays completely stationary. I guess I should try filing the gap to eliminate the contact and see if that helps at all.

Maybe the spring is bad, they will sit crooked like that when messed up
and considering the age that might be it too if the rest of the tremolo checks out fine.

Helpful to know. I'm not convinced yet that the rest of it does check out fine, but I would think replacing the spring would be an easy fix to try out.

Well, unless you have it mounted in the guitar with the strings on and tuned more or less to pitch it's not going to behave in any way normal right?

That may be. Nevertheless, the reason I removed it in the first place is that it was doing the same thing when it was installed and strung up. It's 55 years old. I know from experience that some stuff doesn't always work right when it gets to be that old.

[timtam]

The possible impediments to that are the gap in the plate through which it passes outside the guitar to anchor the strings (which it should clear)

This is great! Upon further inspection, it does seem to be rubbing against the sides of the gap somewhat. The "front" side of the unit that is opposite the collet doesn't move at all when you press the arm. The "collet side" moves fine, but the other side stays completely stationary. I guess I should try filing the gap to eliminate the contact and see if that helps at all.

I don't recall that that gap/slot itself has been commonly reported as a source of problems, but clearances there are not large, so it could well be. We have certainly mused about the need for the knife edge to be a single, distinct edge (fig4a above). It may also be worth looking to see if one side of the extended 'tabs' on which the knife edges are is bent at all ...

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[LizardKing]

You could spin the spring and see if the lean changes....
It looks ok in those last pics so something odd is going on.