Posted by SeldomDetectdCulprit on December 20, 2002 at 22:14:40:
In Reply to: rotary valve noise posted by Jordan Jay on December 19, 2002 at 21:08:52:
Those responses were great! This one is not funny (sorry).
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Quite often, the linkage is not the problem. - Even loose linkage is often not what makes the worst noise.
Further, loose rotors often are not the noise-makers at all.
A VERY COMMON PROBLEM (and seldom detected) is the STOP ARM not being held down to the rotor stem tightly enough to prevent rattling: Typically, there is some mechanical problem that doesn't allow the center screw (even if tightened down all the way) to secure the stop arm - vibration-free - to the stem. The most common cause of this sympton is the stem sticking up too high, causing the center screw to tighten down on the stem only and not on the stem and the stop arm...
Today, I had two "walk-ins" (I don't solicit repairs, nor accept appointments.) with this very problem: an $8000 McCracken French horn (a factory flaw) and a $12000 Hirsbrunner tuba (problem probably brought about by normal wear and tear)...
...so if this is the particular problem with your VMI, it's not something that only occurs on less expensive instruments, by any means.