Fostex G16 - Page 13

When in the SPOT ERASE mode and, at the same time, more than one SAFE/READY
SELECTOR is ON, ERS-0 will output HIGH level as long as ERASE-I or PUNCH I/O-I
is at LOW level.
REC-0 will output LOW level when in the REC mode and, at the same time, more than
one SAFE/READY SELECTOR is ON.
MUTE1-0 is an output for -12dB muting. It is active at HIGH level.
MUTE2-O is an output for perfect muting. It is active at HIGH level.
When REC-O is LOW or ERS-0 is HIGH, U4 and Q14 will switch on and the master
oscillator will be activated.
3 .1.3 Reel Servo (Refer to circuit diagram for System Control, Regulator)
In this transport the reel servo circuit functions to apply constant tape tension during PLAY
or EDIT modes, and maintain constant tape speed during FAST WINDING and LOCATE
modes.
Tension Control Circuit
Tape tension is detected by the tension sensor circuit whose output is proportionate to move 
ment of the tension arm and the output response is as shown in Fig. 3.3.
Fig. 3.3
For the takeup side, the tension sensor output fed to UI 13-10, is compared with UI 13-9
and output at UI 13-8. Then, passing through a phase advance circuit, is applied to the motor
drive circuit consisting of UI 13, Q5, and Q7 (current feedback is applied by RI 16) to drive
the motor. The motor torque thus created puts tension on the tape which moves the tension
arm, and its position is detected and output by the tension sensor.
As shown in Fig. 3.3, when tape tension rises, the tension sensor output drops and UI 13-8
also drops. In response to this, the motor drive circuit input also drops and as a result, motor
torque decreases to reduce tape tension. When tape tension falls, the operation is reversed
to increase the tape tension.
As a result of these operations, tape tension is maintained at a constant figure. This constant
figure can be established by the voltage input to UI 13-9. In other words, UI 12-1 is the refer 
ence voltage by which tape tension is established. This reference voltage is set by R3 for the
EDIT mode, by R2 for the PLAY mode when UI 22 is ON, and by RI for F.FWD mode when
Q12is ON.
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