Also, I'm a hobbyist, not a professional repair person.
I just acquired a 1977-80 Yamaha FG-375S, Taiwan, with a broken truss rod. The allen key nut looks like its been over tightened, and has the tip of the rod maxed out of threads. Probably bottomed out in the nut.
Has any one ever replaced a rod in this era Yamaha? Any clue if it's a single rod only, or a rod in a inverted U channel?
I'm not going to have time to pull the FB until after Christmas to see what's under there, too much family stuff to do. Hoping someone with previous experience might be able to provide some hands on insight.
A previous owner was going to try to repair it, roughly removed the FB binding and balked at that point. So it hung in his basement around all his woodworking project gathering dust and overspray from finishing processes.
Now it's found its way to me. Nice solid top body with only one clean crack in it. Worth it to me to invest my time to try a repair, so why not try myself.
Thanks in advance.
Are you certain the rod is broken (like does it spin), or is the adjuster just bottomed out? Before you start dismantling the guitar, get the adjusting nut off and get a new one. It might just need some washers.
Thanks for the response. I must have edited out that line last night as I hurried up to post.
The nut and rod turn in unison. Left or right. No movement forward or backwards of the nut after 5 turns either direction.
I put a pencil mark on the rod end for reference to be sure they moved together.
Would it be possible for you to post a picture of the FB binding on the low E side so I can see what type of position dots they used.
All the pictures I've found are from the high E side of the FB.
Unfortunately, I have run away from the cold and snow and will not be anywhere near that guitar until after the first week of April.At that time, I will retrieve it from the luthier and can take some photos, if that will be of any help.
I was hoping that someone with some experience with that particular guitar might offer some insight.
Time for an update.
The finger board is off, and obviously for the second time. I see remnants of two glues under it. Hide glue and what looks like tight bond.
First look tells me it is a single rod and it is not broken, but the mounting flat plate welded to the rod at the heel end has rounded out its routed pocket and can spin in place now. I'm guessing some one maxed out the threads in the nut and continued to apply pressure until the wood failed around the plate.
The rod channel is covered with an oak strip. I don't believe there is a metal u-channel under there. Looks a lot like the rod I see in an old Japanese made Epiphone bolt-on acoustic I have.
Remnants of glue and wood chips shook out the dovetail pocket. I'm guessing again that some one removed the FB, tried to stabilize the rod plate in place with wood wedges and glue inside the dovetail pocket. This failed again under pressure when trying to loosen the nut, it just re-cut the plate pocket round.
I'm going to have to ask a few new questions here.
I can steam out the neck, grab hold of the plate and try to loosen the nut. Then devise a way to re-stabilize the plate into the heel. Any insight on re-stabilizing this plate?
Anyone ever replace a single rod style with a U-channel model set up? I think I can route out the channel in the neck if this is a viable option. Pro's, con"s?
Hope to hear someone with some hands on experience with this issue.
I went ahead and tried to pull the neck. But it separated too easily on a previous repair, leaving 3/4 of the heel still mounted in the dovetail. This old repair was not aligned exactly and the added space was filled with glue. It required a lot of cleaning out of old glue. But I believe I'll get a clean break now I can align much better when I get to that point.
What I have now is a break that exposes the last 3/4 inch of the rod on the neck side.
Also I can see that the stop plate at the end of the rod has either compressed or worn away the neck wood to enlarge and deepen the pocket. This allowed the rod to move forward in the neck and aided in the eventual bottoming out the threads.
Never worked with this situation before. I've got to be able to stabilize that stop plate from rotating and hold its position.
Since the rod is out I could drill two small holes in it and put pins or small screws through it and into the vertical surface of the back of the neck. And completely saturate the area with thin CA glue to firm up the wood. Do you think that would be strong enough to hold the plate stationary?
Maybe pull out the remaining heel piece, drill 4 holes in the stop plate and stabilize from 4 points instead of 2.
I'm going to have to use some dowels to reinforce the neck/heel repair too.
I could have a friend who welds add a vertical piece of steel that could descend into the notch in the heel, using the notch as a new pocket guides.
Would I be better off adding a U-channel truss rod assembly into the neck?
I've never made a new neck before, so I don't think that's an option I want to tackle now.
Any insight would be greatly appreciated.
Dave, I've measured the rod and it is 5mm, thread pitch is .8mm, course thread. Pitch was determined by measuring the travel of the nut over 10 revolutions. From what I can find on the web, a fine pitch would be .5mm
I will go out and confirm the pitch tomorrow by matching it up at a specialty shop.
If it was me and my guitar I would take the nut off, pull out the old truss rod, toss it, clean up the rout for the old truss rod and fill it with a well fitting insert, rout that for a double acting truss rod and then try to fix the broken neck. I would probably install a dowel or two to reinforce the neck heel splice. The advantage, to me, of the modern double acting truss rods is that they install directly under the fretboard and keep the neck as thick as possible under the channel. The disadvantage is that they bear directly on the underside of the fretboard so it has to be glued on well.
I'm with Brian on this one, a double acting rod "drop in" repair fixes the problem once and for all.
However, to check threads I have a handful of labelled "likely suspect" nuts, bolts and ferrules, which cost nothing much, to check threads. Reason I have these is that when Tonepros shifted production centers in Asia they also changed their metric threads on their tail piece studs from something to something else - which became a compatibility nightmare. Not to mention Schaller studs (Germany) which were incompatible with all Tonepros metric threads from the get go. Tonepros also make Imperial threaded components which further adds to the mix.
I have TPI gauges but generally like to thread check against a know component just to feel assured. Belt and braces sort of thing.
It's easy to confirm the size If you're in the U.S. Most of the big chain hardware stores (ACE, True Value, probably Lowe's and Home Depot) and probably bigger independents have a big section to sell loose fasteners of all kinds. If so, they'll have a sizing board that has threaded studs for all the common metric and SAE thread sizes, both nuts and bolts. Take the rod to the store, thread it into the stud that fits and you have your diameter and thread pitch.
That works unless the rod is knurled at the end and can't be unscrewed.