SYSTEM FOR CONTROLLING TENSION SERVO OF MAGNETIC TAPE

PURPOSE:To always take up a magnetic tape with fixed tension by detecting a change in air pressure by utilizing an air lifter function and feeding back the change to a tension servo circuit. CONSTITUTION:When an air lifter function is actuated, a magnetic tape 2 is floated from a magnetic head 1 by the pressure of blown air and the amplitude of data read by the head 1 from the pate 2 is changed. The data read by the head 1 are inputted to a detecting means 18 through a preamplifier circuit 17. The means 18 compares the amplitude of the input with a prescribed value and converts the input into a digital signal corresponding to the difference from the prescribed value. The digital signal is sent to an adding means 19 and the means 19 adds the value of the digital signal to a control signal sent from a pressure conversion circuit 13 based on the designating signal A of the air lifter function and performs offset correction. The offset-corrected control signal is sent to a tension servo circuit 14. The circuit 14 controls a machine/ file-reel motors 15 and 16 in accordance with the running direction of the tape 2 based on the offset-corrected control signal. Therefore, the tape 2 can always be taken up with fixed tension.