Abstract: A magnetic disk apparatus utilizing both fixed and removable disk mounted on a common spindle, wherein a first head-positioning device for supporting a first group of magnetic heads cooperating with fixed disk and a second head-positioning device for supporting a second group of magnetic heads cooperating with removable disk means are independently controlled in operation; a drive spindle, fixed disk, first group of magnetic heads and first head positioning device are received in an enclosure, which is removably mounted on a base casting and shot off from dust particles; the removable disk is exposed to the outside of the enclosure; and the second head-positioning device is securely mounted on the base casting.

Abstract: The apparatus of this invention has an electric motor assembled integrally with a motor brake for rotating a magnetic disc, a rocking arm fitted at its tip end with a magnetic head, and a rotary solenoid to shift the magnetic head by getting engaged with the rocking arm, energized by a spring so as to rock in one direction, and is so constructed as to stop and lock the electric motor and the magnetic disc by operation of the motor brake, when power is cut off, and to turn the rocking arm until the rocking portion of the rotary solenoid is rotated in said one direction by the force of the spring to shift and lock the magnetic head to a landing zone defined within the magnetic disc, thus preventing the magnetic head and the magnetic disc from rubbing or running against each other when the power is cut off.