Leaks in horn

[Tubadork]

Hey,
So I think that my horn (PT6) is leaking. Let me know if I am doing this right. I took out my main tuning slide and put my hand over the end of the tuba that I took the main slide out of (the one closer to the valves) and blew air. I felt some air (not much) moving through the horn and a small hissing sound (somewhere, I couldn't hold, blow and find the sound {gosh that sounds like a joke waiting to happen})
Anyone know how to find the leak and then repair it (I don't know any good repair guys in Seoul. D'OH!).
thanks,
Bill Pritchard

[smurphius]

Check all the spit valve corks carefully first of all. If it's making a hissing sound without any valves down, then that only leaves your main slide cork. If that is not the problem, carefully look over all the solder joints to see if anything has come loose. Is this a rotor or piston tuba? The valves may be vented as well depending on what type of work has been done on the tuba. If it is vented valves, then your problem might not be a problem at all!! Best of luck with your endeavors.

[Jay Bertolet]

If you can isolate a general area of the horn that the leak may be in, try covering that area with a soap and water solution. The leak, when you blow through the horn so treated, will cause the area around it to bubble. If you have access to a swimming pool, you might also try that. Submerge the horn, play on it, and see if you can spot the air bubbles. Might look funny but will probably work.

[Dan Schultz]

Before starting to check for leaks, do the obvious things like check piston/rotor alignment and excessive piston wear.

A leak that is bad enough to cause tone instability is usually pretty obvious. In cases where I have to 'track down' a leak, I go to my nice quiet shop and begin by isolating sections of the horn beginning with the leadpipe. First... oil the valves or rotors to help seal them. You will usually always hear a slight hissing coming from the valves or rotors. As far as vented rotors are concerned, there should be no air moving from the vent ports when no keys are pressed. The only time the vent hole is exposed to atmosphere is when the rotor is actuated. If the leadpipe is suspect, it can be tested by removing the 1st valve slide, actuating the 1st valve, and placing your finger over the open slide tube while blowing into the leadpipe. If all is OK, insert one tube of the 1st slide into the intry side of the valve circuit, put your finger over the other end of the slide and blow again. Keep working your way through until you've checked all the valve circuits. If you haven't got enough fingers to plug openings... try using wine bottle corks trimmed to fit.

Holding a tuba under water while checking for leaks is a task for the very robust. You might need a few friends to accomplish this. Never use a compressor to induce air into the horn. The pressure could cause major problems.

[jtuba]

I want to hear what happens when you take your PT6 to the post gym to find your leak. You might even make AFN evening news.