Author: jhoyla
Date: 2007-12-31 08:23
If I understand your description of the suction test results, your top joint is not holding a vacuum for any appreciable length of time, correct? Nevertheless, you cannot find an obvious problem, even with a glass. The corks look new and seal all the way round.
If you know a smoker (and can stand the residual taste this may cause), ask her/him to blow smoke through the top joint while you hold it shut at normal pressure, blocking the bottom of the joint. See where the smoke appears. Your partner should wear a dark sweater, and do this standing under a light.
Please make sure you check the area of the C# and D trill tone-holes very carefully, for this is a prime area for cracks. Wood breathes and warps with age, and even a well-sealed crack can open with time (which is why many repairers will pin a crack closed). If the crack is through one of the tone holes it may need bushing (drill out the hole, thread it, screw and glue in a plastic insert of the correct diameter).
Another possibility is that there is a leak through one of the pads with holes in the middle, due to shellac shrinkage. Here, the air is leaking out through the center-hole in the pad, and then round the outside of the pad under the cup. The only way to confirm that this is the problem is to remove the whole key, and test the pad individually using a rigid tube of some sort to seal against the cork around the center-hole. A smaller diameter pad-punch is good for this.
We'll get to the bottom of this eventually!
J.
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The Oboe BBoard
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