Marantz SD9000 - Page 10

3. Circuit
This Section is intended to explain the functions of the
motors, solenoids and related circuits.
3.1 Motor and solenoid
(1) Play motor (M001)
This FG servo DC motor is always rotating while a
cassette is loaded and drives the capstan, i.e. the tape, at
a constant speed. Winding torque is applied to the right
reel disk during the PLAY or REC/PLAY mode.
(2) Reel motor (M002)
This FG servo DC motor is used to set the tape in FF,
REW or CUE/REVIEW mode (CUE and REVIEW are
performed in the fast forward and rewind modes res-
pectively while programs are being played).
In each mode, the tape speed is maintained constant by
means of the servo control system of the motor.
The reel motor rotates in the reverse direction when
the deck is changed from the fast forward mode to the
rewind mode. Either the left or right reel disk is driven
according to the direction of the motor.
The reel motor is also used to remove slack in tape.
(3) Play solenoid (LOO1)
This solenoid functions when the deck is in the PLAY
or REC/PLAY mode.
a. The head base is lifted and the head contacts the
tape.
b. The pinch roller contacts the capstan and the tape
starts running.
c. Slight braking is applied to the left reel disk to pro-
vide back tension to the tape.
d. The fast forward idler is set in the neutral position.
(4) Brake solenoid (LOO2) ;
This solenoid functions when the deck is in the PLAY,
REC/PLAY, FF, REW, or CUE/REVIEW mode.
When it operates, the left and right reel disks are released
to drive the tape.
(5) CUE/REV solenoid (L003)
This solenoid functions when the deck is in the CUE/
REVIEW, PAUSE or REC/PAUSE mode.
In the CUE/REVIEW mode, the head base is lifted up to
its middle position to permit the tape to contact the
head. In the PAUSE or REC/PLAY mode, the capstan
is released from the pinch roller and, at the same time,
the play idler is disengaged from the reel to stop tape
movement.
(6) Recording/Playback Mode Change Relay
This relay is energized when recording or playback, and
recording-pause mode, and connects the recording head
to the recording amplifier, activating the bias and erasure
| circuitry. When this relay is deactivated, the oscillator
; circuit is switched off and the recording head is con-
j nected to the between-program sensor for programming
function. ,
3.2 Back-up Circuit
When the power switch is OFF, back-up power is sup-
plied to the microcomputer via TO02, rectifier (0419,
Q424) and voltage regulator circuit (0421 ~ 0423).
In this case, the voltage at Pin 36 of Q701 is OV, thus
time is indicated on the display.
During back-up operation, the programs stored in
memory remain uncleared.
3.3 Solenoid drive voltage select circuit
The SD8000 is equipped with 4 solenoids. To ensure
proper operation of these solenoids, a sufficient drive
current is required.
If a large current flows into a solenoid, the solenoid is
overheated which, in turn, increases the winding resist-
ance and reduces the force of attraction of the solenoid.
However, once the solenoid has been operated with a
large current, it operates stable even with a relatively
smal! current.
The SD8000 employs a solenoid drive voltage select
circuit to select the operating voltage according to
whether the solenoid is in the operating mode or holding
mode.
Fig. 3.1 and Fig. 3.2 show the operating principles of
the circuit in the PLAY mode.
Fig. 3-1 Solenoid drive voltage select circuit
29v Q432 PLAY BRAKE —_CUE/REV
Fig. 3-2 Solenoid operation
PLAY H
signal L
Q529 me
ON
Q534 base
OFF
Q534
ON
OFF
Q533
ON
Q532 Base
Q432 Emitter
PLAY solenoid
L001 (both ends)
OV
lOV
About 0.1 sec.
About 1.5 sec