Double Bass Tuner Problem

[gypsydjango]

Problem with one of my tuners--D string--all the others are OK.
The tuner itself works OK, but as the string gets up to pitch the tuner gradually gets tighter and tighter. When the string is near to pitch there is so much tension that great force is required to finally to reach the D note--as if something is going to give. I have lubricated the cogs on the tuner to no avail. Could the problem be that the shaft of the tuner is binding in the hole in the peg box? To slightly widen the hole? Have you experienced this problem? See photos.

 

[RattleSnack]

I would take it apart and check if anything is bent. There is lots of tension there and as it gets higher, imperfection makes it much harder to tune.

 

[bassmanbrent]

Does the tuner only get tighter the more you turn it, or does it slack off a little during part of the cog's rotation and then tighten up again?

 

[gypsydjango]

Thanks for your replies so far.
bassmanbrent--The tuner gets tighter the more it is turned. When the string is slack the tuner turns as normal and gradually gets tighter as the string is up to pitch. When the string is almost up to pitch it takes an effort to turn. The string does not slack off during rotation. The cogs look in good shape. Two attachments of the tuner are attached. One photo is of the tuner key and cogs. The other is the other side of side of the peg box and shows the screw that holds the tuner shaft in place. Could the tightness perhaps be that the screw is to tight and needs to be slackened? (I do not know--just a guess.)

 

[Don Kasper]

It is possible that the axle shaft is loose in the pegbox, and as the string pulls up to pitch, the axle is pulled toward the worm gear, (the spiral gear), causing the teeth of the round gear to be forced into the worm gear This causes the whole system to bind.
You can test this theory by releasing all the tension on the string, (remove it from the axle), and see if the axle is "sloppy" in the pegbox, esp. the side on the round gear side, as well as the opposite side.
The axle should NOT be sloppy in the pegbox, if it is, a qualified luthier can easily solve the "sloppiness". (I used thin brass shimstock wrapped around the axle shaft side of the pegbox, which eliminated ALL Slop and enabled the whole system to operate without any binding.)
Just my $0.03. (Although 25 yrs. ago I did install Rubner tuners, similar in design to yours, and they continue to operate smoothly to this day.)
Good Luck.

 

[1st Bass]

I can’t see for certain: is the string binding against the pegbox wall?

 

[GretschWretch]

I can’t see for certain: is the string binding against the pegbox wall?

Didn't appear so to me. This is a reach but, could the string at some point be binding in the nut slot, thereby creating more resistance to get it finally up to pitch?

 

[John Chambliss]

In one pic it almost looks like the D string is binding in the G string windings instead of sliding above it. If it’s not, I would take off the D string and open up the tuning key. May just need a little cleaning and candle wax inside?

 

[Jaygetsreal]

I have the exact same problem, same string, but mine is an inexpensive Chinese-made DB so my experience may not be relevant.
I took the mechanism apart and found two things.

Firstly the the angle the peg hole is drilled into the peg box is not quite perpendicular to the outside face of the pegbox, meaning that when the peg turns it's not well supported on the opposite side. As the string gets tighter the friction on the reduced contact area increases to the point where - as you describe - it feels like something's gonna give.
The second thing is the peg holes for all 4 pegs, on both sides of the box, are quite a bit larger than the pegs, like there should be a bush in there or something. This adds to the first problem above.
I have not found a fix for it yet.

 

[gypsydjango]

Many thanks for all your knowledge--much appreciated. Will investigate all possibilities.

 

[KUNGfuSHERIFF]

I’m guessing this is an old French bass that was originally a three-string, and the D-string tuner isn’t original?

 

[gypsydjango]

Many thanks everybody for your knowledge.
I think I have found the problem of the D sting as mentioned in my post. This afternoon I had another good look at the tuner. Cogs OK. De-tuning the string the tuner got easier and easier as the pitch of the string lowered. Took the tuner off.I thought the shaft of the tuner looked a very tight fit into the holes in the peg box. So with a smooth round file and various grades of sandpaper I just very gingerly opened up the holes in the pegbox. Put the tuner back on--tuned the string to pitch--very smooth all the way to pitch--'Bingo!' Back to normal.

 

[Mark_T]

Many thanks everybody for your knowledge.
I think I have found the problem of the D sting as mentioned in my post. This afternoon I had another good look at the tuner. Cogs OK. De-tuning the string the tuner got easier and easier as the pitch of the string lowered. Took the tuner off.I thought the shaft of the tuner looked a very tight fit into the holes in the peg box. So with a smooth round file and various grades of sandpaper I just very gingerly opened up the holes in the pegbox. Put the tuner back on--tuned the string to pitch--very smooth all the way to pitch--'Bingo!' Back to normal.

Is the shaft of the tuner conical at all? Is it possible as you wound the string you were wedging it into the hole?

 

[Brent Nussey]

I have the exact same problem, same string, but mine is an inexpensive Chinese-made DB so my experience may not be relevant.
I took the mechanism apart and found two things.
Firstly the the angle the peg hole is drilled into the peg box is not quite perpendicular to the outside face of the pegbox, meaning that when the peg turns it's not well supported on the opposite side. As the string gets tighter the friction on the reduced contact area increases to the point where - as you describe - it feels like something's gonna give.
The second thing is the peg holes for all 4 pegs, on both sides of the box, are quite a bit larger than the pegs, like there should be a bush in there or something. This adds to the first problem above.
I have not found a fix for it yet.

I had this sort of problem once years ago, and I solved it by slipping a piece of leather in the hole to support the tuner on the opposite side from the gear. Kind of a leather bushing. I thought that the leather might compress over time, but it’s been fine for 20 years now.

 

[gypsydjango]

mjt0229---I did not take note if the shaft was conical or not. What I did was to very slightly enlarge both holes each side of the pegbox--just enough so the shaft did not catch the pegbox. So far so good. String works well.
Good info from everybody.