Double Bass 3/4 Thomann Upright Overhaul

j-stylez

j-stylez

May 20, 2023
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#1
Hey folks! Just acquired a second hand Thomann Upright 3/4 bass. Got a good deal on it and have been eyeing Uprights in my area for a bit. It's my first ever, I only played electrics before.

It came with a bridge pickup and a fishman eq preamp, yet to be tested. I am still learning about Uprights but have my fair share of guita/bass lutherie (electric, archtop, acoustic) under my belt so I figured, whatever problems I'll find, I'll just fix it up.

Here it is!
DSC_0538.JPG


Obvious Problems:
- small splinter on soundpost
- unlevel fingerboard (mostly the extension Part), needs planing
- too much scoop for my Taste
- bridge too high

I never touched an Upright in my life until sunday but these problems are obvious. I read "the-setup-and-repair-of-the-double-bass-for-optimum-sound" and am confident I'll fix it all up.

I have a very precise idea of how I want my basses to play and be setup. Let's see how that translates to this Instrument... Wish me luck, and thank you in advance for your interest, advice, laughs and anything else!
 
#4
I have some scraper blades ready, but I have to remove at least 3mm from the bridge end of the fretboard, over a range of about 10cm. It would take me a hundred years to do that!

I'm also following this guys advice, it seems to be sort of like a "Zen" Thing:

Edit: and thank you for the advice, I appreciate it and will switch to scrapers when I get closer to the target shape
 
#6
Yes, I'm aiming for a little bit of relief, but currently there is about 1cm (because the fretboard extension is warped). Got to plane that down considerably first. The rest of the neck is not too bad, but the obvious thing needs to be straightened out.
 
#7
It's hard to capture on photo, but you get the idea:

DSC_0554.JPG

I've taken down the headstock end of the fingerboard by 1mm, gradual until about the 1/3 octave Region. Also took off about 2mm gradually from the fingerboard extension end, which is warped upwards.

I'll take some more off the fingerboard extension to at least get that even and somewhat straight in itself. The rest will be achieved by taking more material off the headstock end. I dont have to do much to the inbetween Region at all. I hope this way (by not making the fingerboard extension too thin) the board will stay settled and not get the idea to move some more.
 
#8
I think there was some kind of finish on the fimgerboard, perhaps this was also used to repair imperfections in the board. The board has several knots and the grain is not the straightest. Makes sense for a bass in this lowest of all price ranges. I have a couple of tearout spots I will have to deal with as well, but overall the board looks okay.

Transitioned to scrapers now, although I might have to use the plane for a bit more leveling on the extension end, which is still a little high on one side.

What's the recommended approach to fix small imperfections on these Boards, shavings/ebony dust mixed with superglue? Or epoxy?
 
#10
While I'm at it, I am also fixing the fingerboard/neck joint which either was not properly made flush upon Initial construction, or is showing due to the ebony Board shrinking over the years.

Either way, this is much easier to fix than the crooked fingerboard. When I'm done with the neck work, I'll finally consider if I want to make any changes to the neck Profile, and then refinish the neck.

On ebony guitar necks, I prefer superglue with dust to fix small imperfections and the like, because it sands so well. I sand more than I scrape there though. So I think I'll fill in any pores/tearout in the end, followed by sanding. I dont want to scrape over any spots of glue, that would probably cause more tear. I think These spots or repairs are what caused my tearout in the first place (from whatever Material the makers of this bass used to cover up these Spots).
 
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#16
Freshly planed and scraped, the fingerboard looks very different. It will darken more when polished i guess, but the ebony has some dark brown and gray patterns in it, which I personally find nice. These are a lot more visible now. Makes it look like the natural product it is. The manufacturer had some kind of finish on there to make it look uniformly black.
 
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#17
Trying to figure out if I want to (and can) get the nut off. It's hard to make out what glue, I think Standard wood glue. But it's on there very tight and I dont want to break it. But it's hard to get the Part right next to the nut flat with the nut still on there...
 
#18
j-stylez said:
I think there was some kind of finish on the fimgerboard, perhaps this was also used to repair imperfections in the board. The board has several knots and the grain is not the straightest. Makes sense for a bass in this lowest of all price ranges. I have a couple of tearout spots I will have to deal with as well, but overall the board looks okay.

Transitioned to scrapers now, although I might have to use the plane for a bit more leveling on the extension end, which is still a little high on one side.

What's the recommended approach to fix small imperfections on these Boards, shavings/ebony dust mixed with superglue? Or epoxy?
Click to expand...
hide glue, always for everything.
 
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#20
Might be interesting for future repairs, but for this board I'm sticking to my tried and tested CA glue + sanding dust. That has always worked well for me on ebony or rosewood guitar fingerboards.

Meanwhile, I've sanded the fingerboard with 180 and 240 grit paper, then reassembled to test the new fingerboard geometry. I still have to do some more sanding to even out slight scraper marks and a couple of tiny spot repairs.

DSC_0590.JPG


It was exciting to check the actual effect of my work and I'm content that things are coming together nicely. I've now got a very gentle scoop, a little less on the G string side, a little more on the E string side. (about 2.5-3mm at the maximum on the E side, a bit less than the string diameter).

The nut was already too high before I took some material off the fingerboard, so I did some work on that as well.

Next up is dealing with the too high bridge. Once that is adjusted, I'll see if there are any more areas to deal with, then dismantle again and finish sanding and polishing the ebony to a gloss.
 
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