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Distinguished SOTW Member/Saxus Envious Curmudgeon
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Discussion Starter #1
I sent my 12M tranny to a new tech nearby who is fast and cheap, but relatively inexperienced, to have it regulated and one rod straightened.

When I went to pick it up I test played it and the notes from G1 up to C#2 (no octave key pressed) wouldn't speak as the octave key on the neck came open.
The notes using the octave key pretty much played ok.

The tech looked it over and was stumped as to why. I checked the springs..nothing was off...can any of you techs give me a not-too-technical explanation as to what is wrong so that maybe I can coach this guy through it?:?
Thanks in advance....

I have had this 12m for nearly a year now and have hardly gotten to play it because no one over here seems to know how to get the darned thing right.
 

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Distinguished SOTW Member
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878 Posts
Check the cork bumpers within the mechanism. If one of the bumpers is either too thin or too thick (or not even there at all), it will cause the neck key to open. Conn octave mechanisms from this era are really fussy if they are not in perfect alignment. However, once aligned, they tend to stay in adjustment well.
 

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Distinguished SOTW Member/Technician
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Hard to tell without seeing the horn. The basic set-up is that there are two octave holes. From C#2 down, both are closed. From D2 up through G#2, only the body one opens. From A2 up, only the one on or by the neck opens. The changeover occurs when the G key is pressed and allows the one on the body to open and keeps the neck one closed. When the G key is not pressed, there is a lever on it that holds the body hole closed and allows the neck vent to open. I suspect that the upper hole is not being closed by the keywork or the spring is too strong. Octave key springs should be light and the G key spring must be stronger. I suspect binding in the keywork.
 

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Also something to check, the opening of vent that opens when the G key is down. When that vent opens too much it hits the G key where it is connected to the octave mechanism and isn't allowed to open any farther, even though the setup is wrong and it wants to open farther. The result is the extra movement of the octave key being transferred to the key on the neck, opening it a little bit.
 
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