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Hi folks,

I recently did some electrical work on my cousin's 1957 or 58 Gibson ES 125 like the one on this link

http://en.wikipedia.org/wiki/Gibson_ES-125

....only I noticed that the top is getting a bit of a valley down the center. The previous owner had cut a hole for a bridge pickup (also a P-90) and two holes for the corresponding v/t controls below the f hole. This valley is most pronounced at the bridge pickup and the bridge itself. No indication of a sag near the neck pu, or elsewhere really. My concern is that cutting that hole sacrificed the structural integrity of the top. We are not talking about a complete crushing here, instead, the top arches up like it is supposed to but as it starts to round off at the crest of the hill, it starts to dip down leaving about 3/32" - 1/8" gap between the solid stiff, but flexible plastic pickup ring and the guitar top and shows similar sag at the bridge. What is the best method of restoring the proper arch to the top of this guitar???? Should I install a sound post? Please advise. (He wants to keep that extra bridge PU by the way)

After installing new SD Antiquity pups for him, he noticed that the strings were buzzing a bit and it sounded dead acoustically. So I raised the action at the bridge and alleviated some tension in the TR, and now it's a bit high for him but the buzzing issue is better. We both agree that our intense scrutiny of the guitar afterward may be revealing buzzing and fretting out that was there to begin with, that we are only now catching. Though I did not have a chance to really sit down and play the guitar before working on the electronics as it was a quick job just before a show, so I'm going by his experience regarding this new found buzzing.

Could the top have shifted more since installing the new pickups causing the bridge to sag a little resulting in more buzz?

As a side note, just in case it was just a case of him not noticing it before, I picked up some other guitars of his and found his 63ish Epi Riviera was in serious need of TR adjustment as it had a critical backbow causing much string buzz, though the action was low like he likes it. He had not noticed a problem with this guitar. This makes me think the the Gib 125 is, as it was, before I worked on the pups. Just my thoughts on this issue, but please weigh in....


Many thanks!
John

Tags: Archtop, buzz, sag, top

Views: 596

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"My concern is that cutting that hole sacrificed the structural integrity of the top."

Cutting holes in an instrument designed for acoustic playing is always a bad idea. I have seen these with the holes cut right through the braces, in which case it is a very expensive repair or a slow death. It is also possible that the bridge foot may have caused the crease over time by not being over or near enough to the brace to have adequate support. This can be helped by making a new bridge with a bit wider footprint. Do not add a sound post!

In regard to your buzzing problem, are you sure that the new pick up was not too close to the strings? There are many causes of string buzz if not. Just letting out the truss rod or raising the action arbitrarily does not address the source of your problem. Our host has provided a good tutorial on this topic here: http://www.frets.com/FRETSPages/Luthier/Technique/Setup/BuzzDiagnos...
Hi Paul, and thanks for the reply,

When I replaced the pickups with Seymour Duncans, I did notice that the bracings were intact, however as this was a last minute pickup switcheroo and at his studio, not my workbench, I couldn't really do to much to check if the bracings were loose, though I did tap around a little on them and they seemed solid at the time from my limited testing. I will be getting this guitar on my bench soon to investigate all of this much further. I will check out the bridge as you suggest.

If the bracings are fine, but the bridge seems to be the problem and upon replacement and fitting it doesn't completely solve the problem, what would you advise? Could an extra bracing be made and installed to help support the top after jacking it up into place with a custom made caul of correct shape for the top? Just an idea. I'm pretty new to all of this over all, have acqured some books but occasionally hit a wall, and I appreciate any help you and other can provide.

It's funny, I found that link about the buzz on Frets.com about the same time as you were most likely posting your response. Very, very helpful tips there!

Thanks again!
John

If the bracings are fine, but the bridge seems to be the problem and upon replacement and fitting it doesn't completely solve the problem, what would you advise?


If you mean, will re-doing the bridge fix the deformation, no it won't but it should stop it from getting any worse. If the braces are indeed solid, I would just fit the new bridge to the existing condition and call it done.

So far as the buzzing, I can only make guesses without actually having it in front of me. It is a process of elimination. Go through the buzz diagnosis list and start eliminating the possibilities. It may be a combination of problems that give rise to the buzzing and not just a single item from the list.

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