Easy neck straightening with a Yamaha SB-5A
Posted: Sat Jan 27, 2018 9:02 pm
I've been wanting an early weird Yamaha for a while, and recently I picked one up on eBay when the biding didn't go too high. It looked pretty good in the pictures, at least!
It appeared pretty good when it arrived too, though I had a bit of panic when I saw that it was just shipped with its case in an open-face cardboard box covered in kraft paper, with no padding around the case and a big hole ripped in the kraft paper.
I played it for a bit just to make sure that nothing was wrong with the electronics, but when I disassembled it for a good cleaning, I found that the neck was held on by only one screw (...with a weird thread pitch that makes finding a replacement pretty tricky)
Also, the height screws on the bridge were either missing, glued in place, or replaced with 4-40" allen screws. ...and one was drilled out so that no threads were left. I needed to drill out the stuck screws.
I wound up drilling and tapping them in an easier to find M4 size - it turned out pretty well, I think!
Another problem was that the neck had quite a bit of backbow - To get the strings to pull the neck straight, I needed to tune the bass to A-D-G-B! I checked out a bunch of videos on Youtube about straightening bowed/twisted necks, and the solutions all seemed pretty drastic - clamping a neck and putting it in an oven, pulling out the frets and putting in frets with a different width tang, pulling off the fretboard and planing the neck flat... I figured that I would try something a bit less destructive and see if it would work.
Here's what I tried on a test subject (Teisco bass with a twisted neck)
-I found a big flat board and clamped the bass's body down
-Using some shims and clamps, I clamped the headstock so that the neck was bent back in the correct direction (I bent it a bit past where I wanted it to go, expecting it to spring back when the clamp was released
-Next, I used a hair dryer on "high" to apply heat to the neck for an hour. At one point, the fingerboard popped off about an inch at the nut, but I glued and clamped it back in place.
-I let it cool down overnight before I removed the clamps
When I removed the clamps, the neck didn't spring back as much as I thought it would - I wound up with a neck that was less twisted than before - but in the opposite direction! Also, the neck seemed to bend more where the wood was thinner - next time, I'd concentrate the heat more where the wood of the neck is thicker.
I tried this method again with the Yamaha - except I used shims to bend the neck up so that it had just a bit of relief. I didn't want to overdo it!
...this time, the neck sprung back quite a bit when I took the clamps off the following morning - though, now the neck is perfectly flat when the strings are tuned to E-A-D-G. Hooray! I might try the hairdryer thing again, except with a bit more bend put into the neck.
It appeared pretty good when it arrived too, though I had a bit of panic when I saw that it was just shipped with its case in an open-face cardboard box covered in kraft paper, with no padding around the case and a big hole ripped in the kraft paper.
I played it for a bit just to make sure that nothing was wrong with the electronics, but when I disassembled it for a good cleaning, I found that the neck was held on by only one screw (...with a weird thread pitch that makes finding a replacement pretty tricky)
Also, the height screws on the bridge were either missing, glued in place, or replaced with 4-40" allen screws. ...and one was drilled out so that no threads were left. I needed to drill out the stuck screws.
I wound up drilling and tapping them in an easier to find M4 size - it turned out pretty well, I think!
Another problem was that the neck had quite a bit of backbow - To get the strings to pull the neck straight, I needed to tune the bass to A-D-G-B! I checked out a bunch of videos on Youtube about straightening bowed/twisted necks, and the solutions all seemed pretty drastic - clamping a neck and putting it in an oven, pulling out the frets and putting in frets with a different width tang, pulling off the fretboard and planing the neck flat... I figured that I would try something a bit less destructive and see if it would work.
Here's what I tried on a test subject (Teisco bass with a twisted neck)
-I found a big flat board and clamped the bass's body down
-Using some shims and clamps, I clamped the headstock so that the neck was bent back in the correct direction (I bent it a bit past where I wanted it to go, expecting it to spring back when the clamp was released
-Next, I used a hair dryer on "high" to apply heat to the neck for an hour. At one point, the fingerboard popped off about an inch at the nut, but I glued and clamped it back in place.
-I let it cool down overnight before I removed the clamps
When I removed the clamps, the neck didn't spring back as much as I thought it would - I wound up with a neck that was less twisted than before - but in the opposite direction! Also, the neck seemed to bend more where the wood was thinner - next time, I'd concentrate the heat more where the wood of the neck is thicker.
I tried this method again with the Yamaha - except I used shims to bend the neck up so that it had just a bit of relief. I didn't want to overdo it!
...this time, the neck sprung back quite a bit when I took the clamps off the following morning - though, now the neck is perfectly flat when the strings are tuned to E-A-D-G. Hooray! I might try the hairdryer thing again, except with a bit more bend put into the neck.