Abstract: Structures and methods are disclosed for parallel biasing and testing, at dc and high frequency, of two or more read heads within a two dimensional magnetic recording (TDMR) slider. Testing of heads comprises both conventional tests of the individual heads within the slider, as well as tests for interactions between the heads which are very closely spaced within the slider and thus may exhibit various magnetic, capacitive, ohmic, and stress-related interactions not seen in non-TDMR heads having only a single read head. Overall testing times are nearly the same as for single head testing.

Abstract: A method for testing a magnetic head to determine whether the magnetic head is unacceptably affected by temperature variations. The test includes testing the magnetic head at different temperatures and measuring either or both of a signal amplitude and a signal asymmetry of a signal from the magnetic head at the different temperatures. If signal amplitude or signal asymmetry vary excessively as a result of the temperature change then the head can be scrapped.

Abstract: A method for testing a magnetic head to determine whether the magnetic head is unacceptably affected by temperature variations. The test includes testing the magnetic head at different temperatures and measuring either or both of a signal amplitude and a signal asymmetry of a signal from the magnetic head at the different temperatures. If signal amplitude or signal asymmetry vary excessively as a result of the temperature change then the head can be scrapped.

Abstract: A method for testing magnetic heads formed on a wafer to detect the presence of thermal induced popcorn noise resulting from thermal fly height control. The method includes performing a quasi test on a magnetic head, the quasi test being performed over 400 or more cycles of magnetic field application. For additional test accuracy, the write head can be cycled while 400 or more cycles of magnetic field are generated.

Abstract: An optical disk recorder employs laser drive signals having diverse current or power levels. A scaling digital-analog-converter (DAC) supplies a scaled reference signal to a plurality of scaled DACs. The scaled DACs supply the diverse laser drive signals. Calibrating the scaling DAC calibrates the scaled DACs. A base array of DACs include not only the scaling DAC but a plurality of base array DACs. Such base array DACs control reading operations as well as supplying a threshold current. The threshold current is that laser drive signal current level below which laser 25 does not emit a laser beam. During writing, the CUT current is added to the laser drive currents supplied by the scaled DACs. A desired CUT current is determined by calculating a slope of the laser drive current to emission of radiation. Then the slope is extrapolated to a zero emission point below which no coherent emission of radiation occurs.