Method and apparatus for writing servo-tracks on rotating magnetic

Abstract

Single and double density servo-tracks are written on the servo-surface of a rotating disc pack with a single transducer carried by a transducer head assembly driven by a screw shaft. The screw shaft is incrementally rotated by a first fixed angular distance and a second fixed angular distance when writing single and double density tracks, respectively. The transducer has a gap width greater than the width of the widest track to be written, and the tracks are sequentially recorded by recording a preliminary track having a width equal to the width of the transducer gap, radially translating the transducer by an amount equal to the desired track width, erasing the portion of the preliminary track overlapping the transducer gap to form a track having the correct width and repeating the recording and erasing steps until all tracks have been so recorded. The transducer drive apparatus comprises a pair of solenoid operated latching pawls each engageable with a different driven gear secured to the screw shaft and a driving shaft having an input gear driven by a motor and an output gear driven through a slip clutch assembly. The two driven gears are provided with different pitches and each associated latching pawl is disengaged from the corresponding driven gear to permit a predetermined number of teeth to pass the pawl between successive latchings.