With a few simple, affordable supplies and this step-by-step guidance, musicians and music directors can easily learn to service rotor valves. This can be of great benefit in both emergency situations and as a matter of regular maintenance. While there are many points of service that can be attended to without great investment or advanced skill, there are still many areas of repair (beyond the scope of this article) that must be referred to professional technicians.
Cleaning and Lubrication
As a musical and mechanical necessity, rotor valves have a very tight clearance between the rotor and valve casing and at the bearings. Because of this, any deposits on any part may cause the valve to lock in place or freeze up. This is most likely to be experienced after the instrument has been unused for some time.
Playing the instrument daily tends to keep minerals and lubricants from hardening into deposits. This is particularly true if the musician lubricates the rotors frequently. The lubrication helps the valve shed any contaminants, and fills the space that would otherwise attract water-born minerals, which create deposits.
Often you can free a stuck or sticking valve without disassembly by lubricating the rotor through the slide tubes, and working the rotor stop arm back and forth by hand. Pulling the valve slides, put two drops of valve oil into each tube on the horn. Don’t turn the valve using the levers, but rather by directly turning the stop arm (fig. 1). Also put a drop on the back bearing (after removing the cap), and the top bearing (beneath the stop arm).
To clean a valve requires disassembly. First unscrew and remove the valve caps. If these are frozen, tap lightly on the knurled (grip) area of the cap in a glancing counter-clockwise manner (as if trying to unscrew the cap). If the cap is still stuck, apply a drop of penetrating oil to the joint of the cap and casing, and try again after the oil has been allowed to penetrate.
Loosen the main screw a turn or two, and tap on the screw to release the road or from the bearing. Completely unscrew the main screw allowing the rotor to be pulled from the casing. If you are removing more than one valve at a time, keep them in order so that you can get the router in the correct casing when reassembling.
Protect the rotor by working over a table covered with a soft towel to receive the rotor if it falls. Also protect the bell stem of the instrument so that if a lever arm releases, the spring tension won't slam the lever into the bell causing a dent. Control the levers while tapping the rotor loose.
The rotor is now available for cleaning. While a scrubbing in soap and water may bring results, more often you will need to soak the rotor in a chemical to remove deposits. White vinegar is a good solution for the non-professional. You may wish to pull all the slides and rotors and give the instrument a brush through in a bath of lukewarm water and mild dishwashing detergent. Rinse thoroughly, and allow to dry before assembling with fresh slide grease and valve oil.
Cleaning the valve casing of deposits is problematic because it requires a larger tank of solution. I would refer this to a technician. Many professional shops use ultrasonic cleaners and more aggressive chemicals for this task.
Wiping both the casing and the rotor with a lint-free cloth, dry test the fit of the rotor. If you are satisfied that the valve rotates freely, reassemble the valve with fresh oil, adding a drop of rotor oil on the bearings and the threads of the valve. Place the stop arm back onto the rotor and set the main screw. Be careful not to over tighten the screw. This task can be clumsy if the string is still attached. You may wish to detach the string and restring it after assembly.
Adjusting rotor port alignment
These instructions include the use of the JLS206058 valve restringing kit