@sheila7a Interesting question. I just realized my current Aerobika and my oldest (spare) don't seem to have interchangeable parts, even though others have easily mixed-and-matched.

As for whether it is working, a correctly assembled, working Aerobika should vibrate when you blow through it, and the intensity of vibration should change as you adjust the lever from minus to plus. You should also here the vibration sound, and the tone should change as the pressure lever is moved. Finally, with your hand on your sternum (breast bone) you should feel vibration in your chest.