Repair of 1975 Gibson J-45

If you have a string instrument of any kind that needs fixing, a mistake you made in building a new instrument that you need to "disappear," or a question about the ethics of altering an older instrument, ask here. Please note that it will be much easier for us to help you decide on the best repair method if you post some pictures of the problem.

Repair of 1975 Gibson J-45

Postby Barry Daniels » Fri Sep 14, 2018 1:41 pm

Up next on my repair bench is a Gibson J-45 dated from 1975. There are several serious issues with the guitar including:

1) A neck with a very bad twist and the need for a neck reset. The guitar is currently unplayable.
2) A bad case of binding rot.
3) Some previous, questionable and poor modifications to the bridge.
4) The need for some new tuning machines and pickup.

Someone also previously removed the shrunken pickguard and repaired a top crack next to the pickguard, but this needs a bit of additional work. All in all, this is a nice guitar but there is a ton of work to restore it. My goal is to get the neck back into playable condition and to replace the binding without having to do any re-spray on the finish because the finish is otherwise in pretty good condition except for a couple of deep scratches and a case of buckle rash on the back. Also, do you see anything unusual about the bridge? More on that later.

By the way, I started this repair about three weeks ago so I have a bit of catch up to do to bring you'all up to speed. So you will see a flurry of posts here.
Attachments
IMG_1052Resized.jpg
Last edited by Barry Daniels on Wed Oct 24, 2018 10:33 am, edited 2 times in total.
Reason: Date change
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Fri Sep 14, 2018 1:45 pm

Here is the twisted neck. It is about the worst that I have seen. I am afraid that the heat set method that I have used in the past on several guitars will not be sufficient by itself to fix this and keep it in place. We may need some additional measures like installing carbon fiber rods. What is unusual is there is no readily apparent cause of the twist. The grain of the neck looks straight, although I can see that the neck is three pieces of maple. Also, when I grab the peghead I can twist it a surprising amount. Something is loose in there and I am seeing the need for some major neck surgery. But my client wants to keep the guitar as original as possible so a new neck will only be made if this one is unsalvageable.
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Fri Sep 14, 2018 2:01 pm

Looking at the back of the neck, it appears that the center lamination is a bit proud. And moving the neck with hand pressure makes it appear that the laminations are moving a bit. I think the two joints are a bit delaminated in the area of the nut.
Attachments
IMG_1001Resized.jpg
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Fri Sep 14, 2018 2:04 pm

Also, someone has previously removed and reglued the fretboard because I can see a 1/32" glued filled gap under most of the fretboard. Also, I can get my seam knife under the fretboard up to the 1st fret without any effort. The fretboard is brazilian rosewood so we will definitely be saving this.
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Fri Sep 14, 2018 2:08 pm

The fretboard was easily removed with a bit of heat. And then I saw something very interesting. The truss rod nut is a bit off-centered. Was it built this way? Could this be the cause of the twist? I need to dig a bit further.

By the way, that is a new nut I placed on the truss rod. The original one was completely rounded off. I had to remove it with needle nose vice grips.
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IMG_1039Resized.jpg
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Fri Sep 14, 2018 2:35 pm

Time to dig out the truss rod. A bit of chisel work and out it comes.
Attachments
IMG_1051Resized.jpg
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Fri Sep 14, 2018 2:40 pm

The actual slot does not appear to be off-centered. Also, I can see that a bunch of compression is present under the truss rod nut. I looks like the washer has compressed the hard maple 1/8". And during this compression the end of the truss rod has slipped sideways towards the bass side of the neck. I also see that some of the neck wood right under the nut has erupted due to the compressive forces. This is starting to look like a serious case of truss rod over-tightening. They may have been trying to avoid the neck reset issue by going crazy with the truss rod. And I think this is what caused the truss rod washer and nut to slip sideways resulting in the twist. I can't believe that someone could compress hard maple this much without snapping the rod.
Attachments
IMG_1057Resized.jpg
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Fri Sep 14, 2018 2:50 pm

So the repair plan for the neck that I formulated is to:

1) Heat set the neck and fretboard to get them into a straight position without twist or excessive bowing (I forgot to mention that the neck is also bowed up about 1/16").
2) Rout slots for two carbon fiber bars and install them.
3) Get rid of the original compression rod (the cause of all this mayhem) and install a modern dual-action rod because this will cause no additional compressive forces on the neck.

The guitar goes into my "Teeter Neck Compensation Jig" with a long board clamped on the peghead to unwind the twist. Some heat from a heat blanket and the twist is taken a bit beyond straight and then allowed to cool. It came out pretty straight. I am going to take a break and get back to the shop now. Feel free to post any questions or comments. I value your input.
Attachments
IMG_1061Resized.jpg
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Re: Repair of 1968 Gibson J-45

Postby Aaron Helt » Fri Sep 14, 2018 6:59 pm

Barry, I really appreciate the repair story. Nothing works to learn from better than seeing it done. Thanks for taking the time.
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Fri Sep 14, 2018 8:06 pm

Glad to do it Aaron.
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Re: Repair of 1968 Gibson J-45

Postby Gordon Bellerose » Sat Sep 15, 2018 12:22 am

Barry,

I really appreciate the time you put into taking pics of these detailed, and difficult repairs.

Your experience is a great thing to witness.
I need your help. I can't possibly make all the mistakes myself!
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Sat Sep 15, 2018 9:17 am

Thank you Gordon. There are a couple of unusual challenges in this job so I thought it would be a good candidate for presentation.
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Re: Repair of 1968 Gibson J-45

Postby Mark Wybierala » Sat Sep 15, 2018 11:23 am

My hats off to you brother. You are going places that are far too scary for me.
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Sat Sep 15, 2018 3:05 pm

I use to like rock climbing when I was young. Now I like to repair basketcase guitars for thrills.
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Sat Sep 15, 2018 11:33 pm

Now to stabilize the neck with the following:

1) A dual action truss rod made by Mark Blanchard. These things are top notch.
2) Two carbon fiber rods sized .2" wide and .25" tall from Dragon Plate.

This will require cleaning out the old truss rod slot and cutting two new slots for the carbon fiber. Then maple splines will be glued on top of all three. My plan on the carbon fiber is to flare them out near the body so that they provide some resistance to future twisting. Also, I plan on placing the carbon fiber slots to cut into the neck lamination joints up near the peghead transition to lock these two questionable joints together. I will use West Systems epoxy for all of this and will add chopped polyester fiber additive to get as much strength as possible. Since the placement accuracy of the slots is critical I needed to remake my truss rod slot jig.

The jig was made with a piece of 3/4" baltic birch plywood, some toggle clamps to hold it to the neck, a Woodriver edge clamp and router plate, and a small plunge router. Once the base is clamped to the neck, the edge guide can be precisely manipulated to place the slot accurately.
Attachments
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Sat Sep 15, 2018 11:36 pm

The jig took me a few days to build and about 30 minutes to use. Here are a couple of more photos. I added some small stops in the T-track to control the start and end points.

The back of the jig was routed in areas to clear the pickguard and the bracket on my string compensation jig. The jig also has four sliding stops that I butt up to the neck to keep it from slipping. Strips of 100 grit sandpaper were glued on both sides of the big slot to further prevent slippage.
Attachments
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IMG_1070Resized.jpg
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Sat Sep 15, 2018 11:45 pm

The slots turned out really well, much better than my old jig which was a pain to adjust.

The truss rod re-slotting was a bit fussy. The original slot had a curved bottom and the new rod needed a nearly flat bottom. So I lowered the slot carefully to prevent over thinning. I used a round bottomed router bit because the original slot was also round bottomed. I ended up only taking a bit of additional wood from the bottom of the original slot at the lower end, and even less wood up near the peghead in my goal to get the slot flat. I stopped as soon as I got close.
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IMG_1069Resized.jpg
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Sat Sep 15, 2018 11:53 pm

I glued all the stuff in one swell foop. I placed a small jack under the middle of the neck to remove the slight bow, and I still have the neck twist controlled during the slot cutting and the glue up.

The small popsicle sticks are small wedges to place clamping pressure on the truss rod filler strip which was slightly lower in elevation than the carbon rod filler strips.
Attachments
IMG_1073Resized.jpg
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Re: Repair of 1968 Gibson J-45

Postby Barry Daniels » Sat Sep 15, 2018 11:55 pm

This morning I removed the clamps and planed down the filler strips a bit. The neck is much more stable as determined by twisting the headstock. The neck twist is actually a tiny bit in the opposite direction than when the guitar came in. I am OK with that and will deal with it latter.
Attachments
IMG_1074Resized.jpg
IMG_1075Resized.jpg
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Re: Repair of 1968 Gibson J-45

Postby Gordon Bellerose » Sun Sep 16, 2018 12:01 am

I have a couple of thoughts...questions.

Would the jig be simpler with a guide bushing set up? Don't get me wrong, there is no wrong way as long as it works!
On second thought, I realized that with the thickness of the jig, the bit would be sticking out a long way if a guide bushing was used.

Do you think you will have to do something with the neck laminations separating?
Or do you think the heat from the blanket loosened the glue enough for it to reset?
Last edited by Gordon Bellerose on Sun Sep 16, 2018 12:03 am, edited 1 time in total.
I need your help. I can't possibly make all the mistakes myself!
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