Abstract: An alignment control is described whereby the orientation of a turntable can be adjusted from outside of a tank in which an ultrasonic test system operates. The alignment control employs a diaphragm which is mounted over an opening in the bottom of the tank and is formed of a material capable of being flexed while supporting liquid inside the tank. The diaphragm is firmly gripped by a pair of clamp plates respectively located inside and outside of the tank. The clamp plates effectively support the turntable through a drive shaft and bearing with a pivot control connected between the outer clamp plate and an external segment of the tank. External alignment of the turntable as well as external rotational drive are advantageously provided.