Disassembling Thayer Rotary Valves
1. Prepare a clean, soft, lint and dirt free area to work.
2. Remove hand slide and all tuning slides and place bell in work area.
3. Remove all screws and/or strings connected to lever and linkages (note: do not remove the
lever from the horn where the spring is located). If you have double rotors, you may want to
keep linkages separated and lay them out in the order you remove them.
4. Separate the valve section from the bell. This will usually involve loosening two brace nuts
and at least one screw. More for bass trombones.
5. Loosen the nut on the brace between the F tuning slide tubes.
6. Unscrew the lock ring and the valve will separate from the housing.
7. Loosen the screw holding the stop arm on the rotor spindle 2 turns. DO NOT remove the
screw too far or it may bend during next step.
8. Gently tap on the head of the screw with a rawhide mallet until the screw touches the stop
arm. Loosen the screw another 2 turns and tap again until the screw touches the stop arm.
9. Repeat number 6 until the stop arm comes off the spindle and the rotor is free from the top