Teac MT-20D-IO Maintenance Manual page 30

50% during tape movement. The output signal of the monomultivibrator is
converted by the following stage F/V (frequency/voltage) converter into a
voltage proportional to the rotary speed. The motor drive amplifier changes
the base current of the power transistor according to the output voltage of
the F/V converter, and finally controls the motor current.
Since the rotary speed of the motor is transmitted to the encoder via the
tape, a servo loop is formed to move the tape at a constant speed by the
above-mentioned signal flow.
The tape speed is changed over between 90 ips and 30 ips by changing the
setting time of the monostable nultivirator. The start controller generates
lamp waveform to determine the rise time at the start of the tape. As for
the direction controller, the direction of tape movement is determined by
changing over the FWD side motor and REV side motor to each other, and at
the same time, the brake is also. controlled at stop time.
As for the tension controller, the current of the feed side reel motor is
controlled to keep the tape tension constant during tape movement.
- 318 -