After a few emails and phone calls, I discovered very little information is available about older Jay Turser guitars. Jay Turser did not issue serial numbers or date stamp their older models, and Jay Turser is now a division of U.S. Music Corporation. I bought this JTA-Flag300 from an eBay vendor by the name of groovexchange, and that vendor took possession of her when his company purchased a huge lot of inventory from a northeast music retailer that had gone out of business. As a result, the previous owner didn't know much about her either, except that her body was mounted on the wall in the retailer's repair shop at the time of the purchase. So, it seems the only way I will learn any more about this JTA-Flag300 is to take her apart.
I started slowly, looking at the truss rod. Fortunately, the removal of the truss rod cover plate revealed a working Allen wrench-style nut, still intact. I loosened things up, and found it had been turned quite tight. This may have been the cause of the damage I found at the heel end of the neck. With the nut in the fully loosened position, I put a flat edge across the frets and confirmed she has a one-way truss rod that is still in working condition.
Not quite out of the neck repair business on this one, I turned my attention to the heel end of the neck. What originally appeared to be a nut and a broken split shaft is simply the end of the rod in a split shaft channel with a flange that is held flat between the neck and fingerboard. Something happened at this joint that resulted in splitting a portion of wood from the neck heel, leaving some of the truss rod end exposed. Maybe the action was getting high, and the owner over compensated by cranking the compression on the neck with an overly aggressive truss rod adjustment instead of having the neck reset. From the overall condition of the rest of the guitar, that is the most likely chain of events. Getting back to business, the thin portion of spruce from the top plate came easily off of the back of the fretboard with some steam and a sharpened putty knife. I'm thinking it will take removal of the fretboard to properly rebuild the damage to the neck heel.
The neck heel would be only half of what I have to rebuild in the joint. The joint appears to be have been made with a whitish-colored plastic piece that was sandwiched within a dovetail formed by the neck and block. The thickness of this piece of plastic might be what was intended by the manufacturer to adjust and reset the neck angle. Considering how slim the body is at this joint, there is not much material to keep the joint from hinging under string tension. I taped up the surrounding area to prepare for using some steam to clean out the joint, and quickly found it to be of no use with removing the plastic. I'm guessing a cyanoacrylate adhesive was used, and resorted to removing some of the plastic with a small grinding attachment on my Dremel.
Between that possible weak or flawed joint design, and not having a way to replace the broken plastic part, I'm thinking the best option is to convert the dovetail into a mortise and tenon neck joint, using access bolts from inside of the guitar through the neck block and into the neck heel, similar to the way many builders do it these days. The trick will be making it work with such a thin body depth and shallow neck heel.
After some clean up of the neck heel and neck block, I checked the fit of the joint. It was already close to being at the correct angle, with the top of fret plane just shy of the high point of the bridge.
Satisfied with how that was shaping up, I pulled the two parts loose again, reattached that sliver of spruce I salvaged from her neck by gluing it to her top plate, and made some minor repairs at the edges, before writing this entry and calling it a night.