Akai VS-2EGN - Page 45

3) Capstan motor FG 1/5 counter
CUE or REVIEW: H
SUAS
FROM CAPSTAN MOTOR FG
(CUE or REVIEW
S70x5=26850H2
1/5 COUNT DOWN OUT
CUE or REVIEW : H
REC Iv SERVO I2v
The operation is the same as that of the capstan motor
FG 1/7 counter circuit.
i 2 3 4
ics.
Fig. 7-46 Capstan motor FG 1/5 counter circuit
To switch from the 1/7 counter to the 1/5 counter,
TR1 is open circuited.
6 7 8 9 10 it
CAPSTAN MOTOR
FG
| |
| |
| i
1 !
Oz
1c7 @)
[
I
|
!
I | 1 |
\ | |
| i
I i l |
I 1
I i
| |
1 |
RESET PULSE
ic? @
Fig. 7-47 Capstan motor FG 1/5 counter timing chart
3-3 DRUM SERVO CIRCUIT
The drum servo circuit sets the drum speed at 25 rpm/
sec (30 rpm/sec in the case of NTSC system) in the re-
cording mode taking the vertical SYNC signal as ref-
erence.
Servo is applied so that the vertical SYNC signal is posi-
tioned to the bottom of the video track to be recorded
on the tape, and so that the picture switching point
during playback occupies a fixed position at the bottom
of TY screen,
In the playback mode, the drum speed is set at 25 rpm/
sec for PAL/SECAM and 30 rpm/sec in the case of
NTSC. The drive signal is obtained by dividing 4.43
MHz (PAL/SECAM) (or 3.58 MHz in the case of NTSC
system) using the local oscillator circuit of the APC cir-
cuit as a reference.
Since a DC motor is used for the drum motor, the servo
circuit requires a phase control circuit and a speed con-
trol circuit. Accordingly, IC AN6350 provided with
built-in phase control and speed control circuits is em-
ployed.
Service Manual VS-2EGN
42