Pressure Testing

[Dan Schultz]

I know that some of you are repairmen and a few of you have been factory trained. Does anyone know of any tuba (or other instrument) manufacturers have ever or are currently utilizing any means of pressure testing?... whether it be by 'MAG' or water submersion?

[Dan Schultz]

There's a tool that repair-guys buy that (at least in the past) came in a fancy wooden box "M..........nic" brand...or something...??

It has a tube coming out of it and adjustable air pressure. I believe it might also come with some solid rubber stoppers along with some rubber stoppers that fit over the tube, but I'm not sure at all about that.

The thing (whatever the name...??) ain't cheap.

That would be a "Mini-MAG". I think Ed Krause sells it. Made mostly for woodwinds but can be used to test brass, too. Only trouble is... it may detect a leak but won't tell you where it is. Also... the main difficulty with applying this device to brass is that a threshold has to be established to allow for the natural leaks that occur at valve ports.

I'm thinking that a little pressure inside the horn while it's submerged in water would be the best test.

[Dean E]

. . . . I'm thinking that a little pressure inside the horn while it's submerged in water would be the best test.

Connect a bicycle pump to the leadpipe after the water keys have been wired down and the bell has been suitably plugged. Plugging the bell in a way that would not damage the horn would be a challenge because of the sheer surface area (square inches) and force to be resisted.

[Dan Schultz]

. . . . I'm thinking that a little pressure inside the horn while it's submerged in water would be the best test.

Connect a bicycle pump to the leadpipe after the water keys have been wired down and the bell has been suitably plugged. Plugging the bell in a way that would not damage the horn would be a challenge because of the sheer surface area (square inches) and force to be resisted.

Oh... I pressure-test horns all the time. My original post questioned whether any of the manufacturers are doing it. The best way to plug the bell is to shove a small rubber ball down into the throat and inflate it a bit. Normally, I don't try to submerge a tuba but rely on a spray bottle with soap solution to spot leaks. Simply blowing by mouth into a piece of vinyl tubing pushed over the receiver is enough pressure to spot a leak.

Actually... if you are having to wire down the waterkeys... you're already using too much pressure.

[Alex C]

Yes, I talked with the president of the brass division of Gemstone Music and they are pressure testing all of the Nirschl euphoniums and tubas. I assume they are doing it on the horns and trumpets as well.

Hope that helps.

[jonesbrass]

I know Alexander does have the equipment to do it. We took my wife's Alex 103 there about 10 years back, and they used the water submersion test to check the compression . . . the 50's vintage Alex we owned was as good as it gets.
I don't remember seeing submersion testing equipment at Miraphone or Rudy Meinl's shop.

[Jesse Brook]

You can use the mag machine to pinpoint by blocking off the tubes one by one. Then you get a more accurate read on where there are cold solders. You can plug the the mag machine's head into larger plungers for larger tubes.