Conn 88H Linkage and Rotor

[Mamaposaune]

Asking this on behalf of one of my high-school students who bought a used 88H 2 years ago. I think it dates from the late 90's-early 2000's, and has the mechanical (not string) linkage system.
It has an intermittent issue with the trigger sticking, when it's at it's worse it won't move at all. But it seems to be the linkage itself; I can move the rotor easily with my fingers on the rotor arm (I hope that's the correct term.) After adding more oil and jiggling the linkage a bit, we can get it going again.
The other issue is the trigger notes from low F down through T-Db are very stuffy sounding. With great effort, he can get them to open up, but the sound is not even close to the low F in 6th. The notches on the backing plate line up with the rotor, IF they are in the right place the ports should be lining up.
There is the possibility the 2nd issue could be on his end, I can't tell for sure and since the pandemic I am still hesitant to play-test my student's horns.
They bought the horn from Dillon's, about an hour away, but although I have suggested taking it back to be cleaned and checked it hasn't happened yet.

[tbonesullivan]

Hmm, was it serviced before they brought it home? That sounds like their could be an air leak somewhere, or maybe even something inside the F attachment tubing.

As for rotors getting stuck, IMHO it's almost always going to be the rotor. There isn't really much in the linkage that can get "stuck", unless something horrible happened to it. The rotor has far more surface area inside the casing that can get stuck. I had the same problem on two basses I had. They would stick at times when using the paddle, and I thought it was the linkage.

NOPE. They were definitely in need of cleaning and were great after being cleaned. When the linkage applies force to the spindle, it does put some angular force on it, most of which is turned into rotational force, however what is left over can cause binding as it tries to rotate the valve core in the plane of the linkage. When you use your hand, you are exerting purely rotational force in the plane of the rotor.

[AtomicClock]

The other issue is the trigger notes from low F down through T-Db are very stuffy sounding. With great effort, he can get them to open up, but the sound is not even close to the low F in 6th.

Other people will talk about valve alignment, but you're right: it could be the player. You're describing me. It's followed me from horn to horn for the last 35 years. I've had a few discoveries over the past several months that may allow me to put this in the rear-view mirror. But it's been a long struggle.

[Mamaposaune]

Thanks David. I always thought Dillon's cleaned and serviced their horns before leaving the store, but I can't be sure this one was. At any rate, he's had it 2 years and keeps the slide clean, but hasn't cleaned out the bell section. There could be some crud built up in the rotor.
Since suggesting to a H.S. kid that he take the rotor out to clean it would be irresponsible on my part, I'll keep pushing for them to take it back for a full service.
He's preparing for All-State auditions, and, well, we all know Murphy's law.

[tbonesullivan]

Thanks David. I always thought Dillon's cleaned and serviced their horns before leaving the store, but I can't be sure this one was. At any rate, he's had it 2 years and keeps the slide clean, but hasn't cleaned out the bell section. There could be some crud built up in the rotor.
Since suggesting to a H.S. kid that he take the rotor out to clean it would be irresponsible on my part, I'll keep pushing for them to take it back for a full service.
He's preparing for All-State auditions, and, well, we all know Murphy's law.

I know they usually lube and clean them up, but I don't know if they do a full servicing on the valves and such before they go out. It may also have been fine them, and some "gunk" dislodged and made its way down into the rotor.

Ahh.. I remember All State auditions. I think I took most using my King 3B, rather than the Bach 42CO I had at the time. Shoulda kept that horn, though it was heavy. Those auditions always stressed me out, but somehow I made it in to NJ all state Junior and Senior year.

[Crazy4Tbone86]

A stuffy trigger register can sometimes be an indicator that there is a lot of stress in the bell section construction. I have had several players bring multiple brands to me with this problem. Most of them played very differently after the bell was rebuilt with no tension.

I once had a pro bring me a Shires that refused to play the low C (trigger + 7.5 position). The note literally would not play, no matter how hard we tried (I can usually remove wallpaper while playing that note). When I started to disassemble the F attachment tubing, one of the solder joints popped and moved about 3/4 of an inch.......that's some stress! After, pulling it apart and carefully putting it together with no stress (some pieces of tubing needed to be trimmed a bit), the horn played very well in the low trigger register.

Probably not the news that you want to hear. Sorry!

[Bonearzt]

There MOST DEFINITELY can be a problem with the linkage!!

If the ball ends are corroded or otherwise damaged, they will not move!
Unscrew one end and try moving either ball end.
And oiling the balls probably will not alleviate the problem if they are jammed, will need to be replaced.

[Mamaposaune]

There MOST DEFINITELY can be a problem with the linkage!!

If the ball ends are corroded or otherwise damaged, they will not move!
Unscrew one end and try moving either ball end.
And oiling the balls probably will not alleviate the problem if they are jammed, will need to be replaced.

Thanks, Eric. If it were my own horn, I would definitely be doing some tinkering myself, even taking it apart.
His parents are really busy, each working full-time and caring for 4 kids under the age of 18.
I think I will offer to loan him a horn and take it to Dillon's myself. It really does feel like it is the linkage that is binding, but best to let them rectify it.