| 摘要 |
<p>PURPOSE:To evade the occurrence of tape damage, etc., by deciding an abnormality in the change of loss torque with the passage of time. CONSTITUTION:A change-over switch 33 is connected to (a) side, and a reel motor 3 is rotated at constant rotating speed in a state that no tape is loaded. A current MIs flowing through the motor 3 can be detected by a control signal SCs from a speed servo circuit 23. The current MIs is in proportion to the loss torque MTs, and since the aging change of the loss torque MTs can recognized by comparing with a current MIsr detected similarly on a manufacturing line, the abnormality in the loss torque MTs can be decided from the current MIs. When the current MIs exceeds a prescribed range, it is decided that the abnormality occurs in the loss torque MTs. When the abnormality is decided, the constant of an approximate equation which computes a current I is set agains, or a VTR is controlled so as to go down when tape tension F is controlled so as to be kept constant by connecting the change-over switch 33 to (b) side and making the current I in accordance with the a tape winding diameter R flow on the motor 3 by a current servo circuit 32.</p> |
