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Hi Folks,

I've been asked to repair an Epiphone Thunderbird Bass for a local music store.  It's a Chinese made bass with a Gibson Nashville name on the Epiphone bolt on neck plate.  It has major neck issues and upon closer inspection had a really bad repair previously.  The nut was poorly replaced and shimmed with 4 layers of maple veneer, the fingerboard had been broken lose up to about the 5th fret, glued with titebond or a similar glue and had several Maple shims under the fingerboard going up at least past the second fret.  The neck had a radical back bow as a result.  

I loosened the badly glued fingerboard up to about the second fret, which released the back bow somewhat, but noticed that I couldn't find a way to adjust the truss rod.  It's bolt on neck so I removed it as well in case it had an adjustment on the body end of the neck like a Fender might have, but it didn't.  

There is a round cylinder on the end, but no room or flat edges where an adjustment wrench could fit on and no way to adjust the threaded rod, buried deep inside the cylinder. Past the cylinder, the truss rod appears to be square and covered in a black plastic wrap. My conclusion is the the end of the truss rod had broken off and that I'll need to replace it.  This is a new step for me, but the bass is worthless right now and I've offered to try this with the understanding that I won't charge the music store for the job if it doesn't work. A perfect time to try out this procedure!  

With that in mind, I hope the forum will give me advice and feedback as I go along and help"keep me out of the ditches" as we used to say in my old road musician days!

I'm assuming the first stepwise be to drill 2 small pin holes in the fingerboard as location points for later re-assembly.  I have not seen similar neck rod assembly on Stu Mac or Luther's Mercantile websites, but found this on a quick google search that looks similar. Of course, I won't know for sure until I open things up.

If I'm correct about the trussed style, the longer cylinder has sheared off leaving only the shorter cylinder with the broken end of the truss rod inside.  So my proposed plan is to remove the fingerboard, replace the truss rod, then re-assemble. This is all new territory for me and any suggestions folks can make on how to proceed will be graciously and gratefully accepted. I'm somewhat concerned about how much back bow the neck seems to have in the sections I have loosened so far. You can see this in the close up of the truss rod end.  The fingerboard is now essentially flat and the neck bows backward as you can see.  I anticipate there may be other surprises awaiting me as well.  If I get the neck corrected, I'll cut a new nut and work on set up and action.

I would consider myself an early journeyman repairman.  I usually re-build and repair vintage acoustics and can do most anything from neck re-sets to french polishing finish but I thought this would be worthy of my time and efforts and give me a chance to grow my skill set.  Thanks in advance of any support you can share!

  

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Hi Chris, I have learned from past jobs like this to heed the warning signs. When I see a fingerboard separated from the neck the way you describe I have found that the rod has been possibly over tightened to remove a bad neck bow. Also, if I see the adjusting nut damaged I again suspect overtightening to lower action or a seized rod. 

I would check to see if the neck is in good order, I suspect not, and will respond to rod adjustment. A new Chinese neck might be a cheaper option. But where's the challenge in that. The ones I have repaired in the past have all required a different approach.

Good luck. Taff

Hi Taffy,  Thanks very much for the reply.  To the best of my ability to see, I don't believe there is a way to adjust the truss rod at all and I suspect the rod adjustment nut was sheared of by exactly what you are suggesting... over tightening of the truss rod to take out a bad neck back bow. I'm hoping someone has dealt with an Epiphone truss rod before and can recognize if it is complete or not.  The bow in the part of the neck that has the fingerboard freed up from the fingerboard clearly is more back bow than I've ever seen and I suspect it's simply a bad piece of wood. 

Another possible complicating factor is the fact that there is surely glue that has seeped into the truss rod cavity from the sloppy re-glue of the fingerboard. I'm wondering if that is a factor in the backbow of the neck, but the goofy way it was repaired suggests that perhaps they were leveling fingerboard against the backbow by simply raising it up at the nut end.

I completely agree that if this was a repair for an actual customer, the best case would be a new neck.  This one is really off in ways I've never seen before and I fully expect to have other issues to deal with, as yet unseen. I'd guess I'd agree that I'm really curious about all this and see it as a way to explore the situation and hopefully learn from it.  

Hi, this custom bass with a very flexible neck presented with similar issues to your Epi. The adjusting nut Allen key recess had been completely stripped and was round inside, from overtightening.

I decided to replace the rod so removed the fingerboard but could not find a replacement with the same dimensions, so this meant a repair to the original. I cut off the original nut and welded on a new Fender-style bullet nut.

As the neck was so flexible, I decided to straighten it and added carbon fiber slats on either side of the rod slot to stiffen it. I then reglued the fingerboard and dressed the frets.






Thought this may give you some ideas.
Taff

Excellent!  Thanks very much.  This looks like great info and I have to do a fiber rod install on a 1940s Kay K-26 after this project, so it might just be worth experimenting on this one.  Again, another first for me.  Is the plastic piece on the bottom of the Dremel some sort of guide or jig?  The cuts look perfect.

It never occurred to me to weld on an extension to a broken truss rod.  Great idea.  I've managed to get a bit over 1/2 of the fingerboard loosened.  The tight bond glued section came off relatively easily, the the remaining originally glued section is more problematic.  Clearly not a water based glue, but heat does weaken it and I'm gradually working it off.  Still can't determine the exact condition of the truss rod, but should know once I get the board completely off. Oddly enough, there appears to be some sort of veneer under the fingerboard at the body end.  It has original finish on it, so it must have been made that way for some reason.  The bass has the word USED stamped on the back if the headstock UNDER the original finish which makes me think this is a factory second.

Hi, yes I made a special baseplate for my dremal, and put the guide that sits in the existing rod slot offset to one side. 

Taff

This will be fun Chris!

From that photo sighting down the neck I can see  - yes, a hell of a lot of back bow - but also a twisting of the neck (headstock rotated counter-clockwise).  Much as Taffy suggested, and this might have been the problem that the previous repairer was trying to fix?  And now the truss rod is rogered as well. 

I would approach it much as you seem to be planning, and others have suggested.  Remove the FB, remove the rod, assess the shape of the neck, correct by heat or twisting and clamping, and planing to get a true neck, replace the rod, maybe add CF reinforcement, reglue the FB,  and enjoy a celebratory cold beverage. 

before.JPG

after.JPG

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I might as well jump in. I would bet that this $300 new at best bass has a single action truss rod, just a rod and a nut. The adjusting nut has been boogered as previously noted and needs to go away.. The separated finger board might be the result of overtightening the truss rod or an an effort to get at the boogered nut. Perhaps the truss rod broke, leaving a bit of thread. You'll be able to judge this once you've got everything apart. 

If you want to put a new truss rod and reinforcement in this thing, by all means do so. But I think the truss rod may be salvageable using something like the Stew Mac truss rod rescue tool (order before midnight so you don't forget). Frank has an article on frets.com showing how he mad his own truss rod rescue tool (probably the inspiration for Stew Mac...) and repaired a strat neck. He ends up making a long truss rod nut once he exposed some thread. Google frets.com truss rods.

And now, a story.. Back when I was in music retail, an old Jazz Bass with a homemade fingerboard walked in the store. Being that kind of guy, I bought the boogered jazz bass and had a new fingerboard put on. The truss rod nut was deep into the neck. Many years later I said to myself: "Self, why is that nut so deep into the neck?". I removed the nut an found the truss rodd itself was broken off and that's where the nut had to go to function. After searching fruitlessly for an aftermarket extended truss rod nut, I made one. coarse, but functional.

Then I rediscovered Frank's article. I think that this is how this neck could be repaired once the fingerboard is properly affixed. That being said, Thunderbird basses, even the real ones, had rubbery, fragile necks which often required, uh, intervention. So you might be more gratified by replacing the truss rod and putting in some CF. The toe of these necks tend to bend up like an begging cocker spaniel, so keep that in mind.

Thanks very much, everyone.  I'm tied up today, but will complete the removal of the fingerboard tonight and tomorrow and proceed as you have all suggested and share pics.

Taffy, Love the neck jig idea and will try to "steal it" with your permission!

No worries Chris, it's good to be able to give back after years of help from others.

Taff

Mystery solved!  I was able to remove the fingerboard after a second round of heating and low and behold, the answer was right before my eyes!

There was indeed a massive back bow in the truss rod!  I just popped pout of the slot with the fingerboard removed.

You can really see the amount of back bow in this shot on the pegboard.  

Interestingly enough, the neck immediately became straight once the rod was removed so I expect that with a new truss rod, it may work properly again.

I'm new to truss rods, but this does have 2 bars; a square bar over a round bas, so I assume it's a double action truss rod. Any thought on a proper replacement?

Hey looks like you had a win there. I would replace with a rod the same as what came out if possible. But first I would try to find out why would someone overtighten the rod so much in the first Place. What were they trying to achieve and why. I hope the rest of the job goes well.

Taff.

Check the rods at bitterrootguitars.com. There's probably a close replacement there.

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