Looks to me almost like they were over tightened, stripping out the threads. I don't think your AC had anything to do with it, nor do I think it worked loose. Hearing that crack was tension releasing when the threads gave way. It was too tight and stretched the screws just a bit much.
Not corrosion, it's caused by fatigue in the thread when the trem is used with these bolts slightly loose.I should add that what @Piing posted looks like a case of dissimilarity corrosion. Probably something in the pot metal that didn’t get along with the bolt threads.
Edit: at least it was on the example I worked on.
Honestly i can't sonically tell the difference between a steel or brass block. Brass is shiny tho...lolOn minor thing about FU blocks; Why assume that bell brass is good at resonating across a wide range of frequencies found in the guitar? It isn't and who wants their guitar to sound more like a bell? smaller blocks impart less of their (possibly negative ) character on the instrument and allow the string energy to pass through more to interact withe the body. The string energy is governed by how hard you hit the string and if the string can then vibrate freely. If that parts stays the same adding mass to the block literally blocks the string energy reflecting it back in to the vibrating string adding sustain but loosing body interaction . Also being bell brass it imparts IT'S character on what notes it reflects and which it doesn't .
This is why if you have a guitar with a Floyd and dead or over loud notes swapping out the block for a high mass one is a good place to start. But for everybody else all you get is different. You may like it but just as possible that you won't. Hardly an upgrade , more a lottery.
Honestly i can't sonically tell the difference between a steel or brass block. Brass is shiny tho. LolOn minor thing about FU blocks; Why assume that bell brass is good at resonating across a wide range of frequencies found in the guitar? It isn't and who wants their guitar to sound more like a bell? smaller blocks impart less of their (possibly negative ) character on the instrument and allow the string energy to pass through more to interact withe the body. The string energy is governed by how hard you hit the string and if the string can then vibrate freely. If that parts stays the same adding mass to the block literally blocks the string energy reflecting it back in to the vibrating string adding sustain but loosing body interaction . Also being bell brass it imparts IT'S character on what notes it reflects and which it doesn't .
This is why if you have a guitar with a Floyd and dead or over loud notes swapping out the block for a high mass one is a good place to start. But for everybody else all you get is different. You may like it but just as possible that you won't. Hardly an upgrade , more a lottery.
It's not a guaranteed fix but it is something you can try because it is the only way of altering the mass of a key component. It depends on how near the resonant frequency of the neck is to a dissonance with the body. A small change in the block may not always move it far enough to work.At my Suhr Modern Satin with dead note I replaced the slim block with a thicker brass block, but it did not solve the dead note issue and I couldn't notice any difference in tone. That replacement was a waste of money. I have ordered brass for the Lo-Pro-Edge because it is the only one I've found available.
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You don't even want to know some of the extremes I've gone to rid a guitar of that before.It's not a guaranteed fix but it is something you can try because it is the only way of altering the mass of a key component. It depends on how near the resonant frequency of the neck is to a dissonance with the body. A small change in the block may not always move it far enough to work.
That was all VaiI don't know who had the silly idea of sculpting a useless handle at the body.
I'd check to see if a Gotoh fits and if so, I'd replace w that.
And now I have another reason to not cover the ass
And I love the Schaller Tremstop. Quick convert to hardtail and tuning to Drop D or a semitone down without destabilizing the bridge