Ask Dave: What Can I Do About a Leak?

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iStock 000007540398XSmall Ask Dave: What Can I Do About a Leak?Ryan asks:

I’ve been using a older, heavily used Conn 6D until I can afford a better horn. It has a few quirks, but it’s hasn’t been too bad. Recently, any note played using the third valve sounds real weird, as if I’m just buzzing in a long open PVC pipe or as if I took the 3rd slide out of the horn, but the sound still comes out the bell.

I thought it might be a leak, so I took my slides out and tested them all. With my finger stuck blocking each slide’s airflow, I could still blow air in and hear a hissing sound in the bell, on every slide.

So I guess I have two problems or are they related? Any chance the 3rd valve sound could be embouchure related? Any ideas, or is this an automatic trip to the shop?

Dave replies:

These things stick out:

  1. You used the term “recently” so I assume this was not a problem before and is now a problem.
  2. It’s the third valve so it’s an isolated problem.
  3. You tried the rotor which may be leaking based on your test. (Maybe not. This pressure test is not always indicative.)
  4. It seems to be on both sides of the horn, so it is likely we can eliminate the slide tubes themselves, because it is unlikely they both have the same problem (unless the horn was dropped).
  5. This is older, heavily used horn so worn parts are to be expected.

First, I really think we can eliminate embouchure problems. It seems that there were not problems before, and there are no problems with valves 1 and 2, so I doubt your embouchure is at fault.

Second, this sounds very much like a leak which somehow involves the third valve. Check all the tubing joints, and especially those around the third valve. Your horn may have come unsoldered in a place that you least expect but is not apparent until you play third valve. Check the slide tubes for leaks, too, just to rule them out. Cold water in the slide tubes should reveal any problem.

Check the rotor itself for looseness in the casing. And, better to check for leaks by using an extremely heavy oil to seal the valve rotor inside the casing, such as 90 weight oil. You can clean out the heavy oil by pouring in some light oil or filtered lamp oil. Also possibly is that the top bearing plate is loose and is allowing the rotor extreme end play.

The final possibility is that something has gotten stuck in a tube, somewhere. Use of a cleaning snake and/or compressed air can find stuck foreign objects.

This is a long shot, in my opinion. Chances are you have a leaking rotor or a broken solder joint. Either way, it sounds like a trip to the shop to me.

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Dave Weiner is a repair technician in Lutherville, MD, and owns Brass Arts Unlimited, specializing in horn repairs, and sales of instruments and related accessories. Do you have a technical or repair question? Ask Dave!