| 摘要 |
PURPOSE:To detect the deterioration, defect, etc., of a recording medium before the output of the recording medium drops until data processing is disabled by grasping the state of the recording medium by utilizing the output of a servo waveform. CONSTITUTION:Each recording track of the recording medium is read by a write head 20. The servo waveform (a) is amplified by a write amplifier 21, and when timing signal (b)-(e) from a rotor tachometer decoding circuit 23 arrives, an analog peak holder 22 holds the output voltage level of the current servo waveform to send respective held voltages (f)-(i) to an analog switch 24. Consequently, an error due to noise is removed effectively. The analog switch 24 is applied with a reference voltage V0 from a reference voltage generating circuit 25. If the servo waveform deteriorates or has a defect, the held voltage corresponding to the waveform drops below the reference voltage V0. Then, the analog switch 24 is turned on only when the respective held voltages (f)-(i) are within the range of the reference voltage V0 to send the output to a counter 26. |
