Akai VS-2EGN - Page 41

CAPSTAN FG SIGNAL
FG AMP_OUT
Ici @
FF(1) OUT
FF(2) OUT
mm(2) cit @ \
MM(2) OUT |
GATE(2) OUT
ici
@)
Lt
eee
il
|
FF(3) OUT
TRAPEZOID OUT
GATE (3) OUT
$8 H(2) OUT
ici1@) L
GND
Fig. 7-39 Timing chart of capstan speed control system
If the output voltage of the phase control circuit is con-
stant, the output of Mono-Multi 2 has a constant time
period. Accordingly, the GATE output pulse width be-
comes wide, and the charge time of TRAPEZOID 2 be-
comes long. Asa result the peak value of the trapezoidal
wave becomes high, and the output voltage of the Sam-
pling & Hold circuit becomes high.
This output voltage is inverted and amplified by the DC
38
Service Manual VS-2EGN
AMP (TR8 and TR9), and fed to the next capstan motor
drive circuit. It lowers the voltage to be applied to the
capstan motor, causes the capstan motor speed to fall,
and returns the speed (rpm) to the original.
Conversely, when the capstna motor speed falls, the
speed control circuit operates to increase the speed so as
to return the speed to the original value.