Apparatus is provided for a tape head actuator having a guide bearing preload mechanism, wherein the preload mechanism utilizes a magnet or magnets and an elongated steel member. These magnetic components interact to produce a force that is selectively directed to preload the guide bearings. In addition, the magnetic components produce a field used to shield the tape head from stray magnetic fields. In a useful embodiment of the invention, directed to apparatus for a tape transducer positioning mechanism, a carriage is disposed for movement along a path of travel relative to a support structure, to selectively position a tape transducer. One or more bearings are joined to the carriage, to support the carriage for movement along the path of travel. The apparatus further includes a first magnetic component joined to the support structure, and a second component joined to the carriage for cooperatively interacting with the first component, in order to produce a magnetic force that is transferred through the carriage to apply a preload force to each of the bearings.