Abstract: A read/write head unit is moved across a reference burst track on magnetic tape from one longitudinal edge thereof toward the other through a series of transverse locations. The peak amplitude of the output from a read amplifier, representative of the reference burst, is detected at each transverse location. The set of amplitude values thus obtained is then referred to data, compiled by testing a number of tape transports and a number of tape assemblies, representative of standard categories each comprising an allowable range of deviations from a different standard set of amplitude values and a corresponding distance to be traversed by the head unit from the last of the series of transverse locations to the centerline of the reference burst track.