Posted by Robby on November 04, 2001 at 15:19:04:
In Reply to: Miraphone rotary valve maintenance posted by Gilyn Chregmaan on November 04, 2001 at 13:03:22:
I haven't played a rotary in years but I used one alot in H.S. Since you are a fellow geologist I'll throw some ideas around. I work on alot of cars as a hobby and the first thing is to isolate the problem. Try disconnecting the linkage and seeing if the valve moves easily by itself. That way you can determine if it is the valve or the linkage/ball-joint giving you trouble. If it's the valve there could be some sludge or mold in the horn that needs to be rinsed out, or perhaps some oxidation. Another thing is your last valve oil may have reacted badly to your new valve oil and formed some sludge but I think that problem isn't as prevalent on rotaries although anything can happen. If the horn was in storage then hopefully it's not a warped or dented casing.
If it's the linkage there are a number of things to adjust depending on the type, some of which are quite a pain on some horns, I'm not familiar with all aspects since I've only played one rotary horn my whole life. I did adjust spring tension and lap a valve on it, however, if you are busy doing field work in Africa I don't think that is an option.
Others will most likely chime in on this problem since nobody likes to see a tuba down. Good luck with the sluggishness.
RWN