| 摘要 |
PURPOSE:To detect the disconnection of a magnetic head, a fault to set a write current at zero, and the fault to produce the unchange state of a write signal, by inputting a voltage proportional to a part of the write current responding to the write signal to a multivibrator, and observing the level of the output of the multivibrator. CONSTITUTION:When a write circuit is operated normally, either pair of transistors 7 and 18 or transistors 8 and 19 are turned on or off, and the voltage at the point A of the collector of the transistor 18 changes. By setting the voltage of a constant voltage source 23 at an intermediate level between the high and low levels of the voltage at the point A, the voltage at the point A is level-converted via a comparator 24, and is inputted to the multivibrator 25. Meanwhile, when the disconnection of the magnetic head is generated, the collector current of the transistor 18 goes to zero, and the voltage at the point A of the collector goes to the high level, and no triggering of the multivibrator 25 is generated, and the voltage at a terminal 26 goes to the high level, which shows abnormality. In cases where the write current goes to zero and unchange state of the write signal is generated, the fault in every case can be detected similarly. |
