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Despite a lot of effort, my 3rd and 4th rotors make a nice little "clank" sound when I am playing passages that require any real amount of quickness in pressing the 'valves'. Note: The clank occurs when the rotor is fully turned (valve is pressed), much like the whatever-it-is inside the rotor is turning to far and slapping the side of another whatever-it-is.

The linkages are relatively quiet, and I've made sure the rotors are adjusted - the lines are perfectly matched on the back of the rotor. Could someone give me some advice on what this problem might be and how it could be fixed (an overview of how the rotor works, in general, would be nice)? Or if not, just tell me that by virtue of my questions I'm far too ignorant to be messing around with them and should just suck it up and take it somewhere.

Thanks to all,
brad h

brad.horton@gmail.com

Did you check the stops? Maybe the cork/rubber fell off of them? Compare 3&4 with 1&2.

No noise on relesase?

If the 'clank' is happening AFTER the stop arm hits the bumper AND the bumper is in good shape, there's a good chance that the stop arm is loose on the rotor axle. Short of finding a quick cure via the description provided, I strongly recommend that you take your horn to a qualified technician.

If the stop arm feels tiight, then try grabbing the stop arm with your fingers and pull and push it gently straight in and out. If your "clank" shows up there, then you might not have the rear bearing plate seated correctly.

Also, check to make sure that the screws holding your stop block to top of the rotor housing haven't become loose.

I doubt that you've got bearing wear on 3 and 4--wear usually shows up first on valve 1--and I'd be surprised to see much wear on a horn as "new" as a PT-6.

Update: I tried looking for what all was suggested and made a small discovery. The clank seems to be coming from the axle moving up and down a very tiny fraction of an inch - 1/16th of an inch would be my best guess. When I press the 3rd valve, the linkage must be ever so slightly warped and in turn is pushing the whole center part of the rotor down when pressed. Like I said, it is a very tiny amount...just enough to make a clank that is driving me (and a bass trombone player) nuts. Also, when i hold the center part of the rotor up and keep the rotating part from hitting the metal, it doesn't clank.

I noticed that all 5 rotors have a small amount of play in them (when grabbing the center and GENTLY moving them up and down). I'm hoping just bending the linkage a smidgen with some pliers will fix it -- I'll post tomorrow with an update as my wife is tired of me "fiddling with the damned tuba."

If the play in the rotor is a bad thing, PLEASE let me know.

And thanks to all of you for the help!

brad h

horto008 wrote:Update: I tried looking for what all was suggested and made a small discovery. The clank seems to be coming from the axle moving up and down a very tiny fraction of an inch - 1/16th of an inch would be my best guess.

1/16" is LOTS!! If your eye for measurement is good... then you certainly do need to take your horn to a good repair tech.

horto008 wrote:I noticed that all 5 rotors have a small amount of play in them (when grabbing the center and GENTLY moving them up and down). I'm hoping just bending the linkage a smidgen with some pliers will fix it -- I'll post tomorrow with an update as my wife is tired of me "fiddling with the damned tuba."

Do NOT bend the linkages--your problem is not there, and if you bend them then you'll have two problems.

The problem sounds like the rear bearing plates need to be adjusted. This requires gentle whacking with a rawhide hammer by someone who knows how and where to whack. Doing it wrong will bind the valves, requiring further whacking with a rawhide hammer to make things straight again. It's not hard but do you really want to learn how to do this by experimentation on your multi-thousand-dollar PT-6? As we used to say in racing, Don't race your ride.

Rick "who recommends listening to one's wife" Denney