Dust-immune method and apparatus for gain control of a read amplifier in a magnetic tape transport

摘要

A method of controlling the gain of a read amplifier preparatory to writing data on a length of multitrack magnetic tape, by writing and reading in a read-while-write mode a reference pattern on the tape immediately when the tape starts running. The gain of the read amplifier is automatically controlled so that the output therefrom, representative of the reference pattern read on the tape, may have a magnitude within a predetermined range. The gain control procedure is retried up to a predetermined number of, say, fifteen if the output magnitude of the read amplifier fails to come up to the predetermined range. If the failure in gain control is due to dust accumulation on the tape or on the transducer, the reference pattern is increasingly more likely to be written and read properly during the retries because the dust may be removed by relative sliding motion between the tape and the transducer.