Dual C 828 Serviceanleitung Seite 5

Outputs
All outputs for the device functions and LED displays come from the
processor as active LOW. The course of signals for PLAY
is used as an
example. The active LOW signal of the processor (pin 29, IC 401) rea-
ches the base of O 422 which becomes reverse-biased, as the result of
which Q 425 becomes forward-biased and applies
O V to the PLAY
magnet. As transistor Q 422 is negativebiased, the HIGH signal reaches
the base of O 423 via C 420, this becomes forward-biased and thus
Q 424 connects an overvoltage to the PLAY magnetic for each period
of time (approximately 200 ms). After the timer (C 420) has elapsed,
Q 424 becomes reverse-biased and diode D 415 holds this until Q 425
switches-off the magnet by means of a HIGH signal from the processor.
This over-excitation ensures rapid and reliable response of the magnet.
This principle also applies to the other control magnets. In PLAY mo-
de, first of all the magnet PLAY is energized and, depending on the se-
lected direction of motion, the magnet FF or REWIND becomes energi-
zed with a delay of approximately 100 ms. Diode D 406 then holds the
selected magnet. The drive motors are activated with transistor Q 409.
A LOW signal (pin 26, IC 401) at its base causes Q 407 to become re-
verse-biased, as the result of which Q 408 causes transistor Q 409 to be-
come forward-biased. The operating voltage for the LED recording
level display is also activated when the motors are switched-on (plug A,
pin 7).
Record standby
Partie analogique
Reproduction
Enregistrement
biased, Q 402 becomes forward-biased and the LED RECORD lights
up. In addition, the transistors O 410 and Q 412 become conductive
and the RECORD magnet is energized. At the same time, the PLAY
magnet and the LED PAUSE are activated by the processor. When
Q 403 becomes reversed biased, the flip-flop IC 404 (C 434, R 431,
D 417, R 430) is reset and the output of IC 404, pin 4 is switched to
HIGH level, as the result of which the oscillator is muted. After the
right-hand motion or left-hand motion (reverse) play button has been
operated, the LOW signal output by the processor is switched to the
flip-flop IC 404, pin 1 via the decoupling diodes D 420 (FF) or D 421
(rewind). In this way, the output IC 404 pin 4 switches with a delay to
LOW level and the RF oscillator is enabled. In this way, inadvertent
erasure is prevented with this circuitry.
Reverse
After the left-hand motion - reverse play button has been operated,
IC 401 passes on a LOW signal from pin 20 to the delay element IC 404
pin 8/9. After approximately 200 ms, transistor Q 413 becomes reverse-
biased as the result of a LOW signal at the output of IC 404 pin 11.
With the HIGH signal at the collector of Q 413 (plug A, pin 6), the dri-
ver stages for the relays RY 301 and RY 302 are switched through. The
normally closed contacts of the relays constitute the reverse switch S 2.
Muting
The muting signal is switched with transistor Q 404. If Q 404 is for-
ward-biased, Q 429 becomes reverse-biased and applies a HIGH level to
the control output plug A, pin 4. Muting is thusactivated (refer to the
description of the analog section). A LOW signal from IC 401 pin 18 to
the base causes Q 440 to become reverse-biased, as the result of which
Q 429 becomes forward-biased after a time delay (C 431) and a LOW
signal is applied to the collector of Q 429. Muting is cancelled. Muting
is activiated by the functions FF, REWIND, STOP and DLL ON.
A l'intérieur du processeur Dolby, le signal se répartit sur deux sorties,
pin 3 et pin 7 de IC 102. A l'enregistrement, le signal de pin 3, qui a
été influencé
par le processus Dolby, passe par le commutateur E-R
S 1 — 7 avant d'arriver à la sortie moniteur (Line) et à l'amplificateur
de l'indication et du casque-écouteur.
Le signal de pin 7 parvient à
l'amplificateur d'enregistrement (Q 112 et Q 113) aprés étre passé par
le commutateur
E-R S 1 — 9. Le courant de conversation se régle sé-
parément pour chaque systéme
de téte magnétique avec VR 107 et
VR 108. L'interconnection se fait avec Q 108 et Q 109 qui dépendent
de la position du commutateur réversible S 2 — 8. Le niveau et la cor-
rection sont adaptés aux différents types de bandes par l'intermédiaire
des transistors Q 111, Q 114 à Q 119. Le signal d'enregistrement est
envoyé à la téte magnétique
aprés avoir traversé le circuit réjecteur
L 103 et la prémagnétisation y est mélangée avec VR 109 et VR 110.
La connection des résistances R 301 à R 310 à l'aide des sélecteurs de
type de bande S 3 Fe, S 4 Cr, S 5 FeCr et S 6 Met influence l'oscillateur
HF de maniére à ce qu'il apparaisse un point de fonctionnement optimal
pour chaque type de bande.
L'oscillateur est rendu Silencieux par un
signal HIGH à la base de Q 305. Le courant d'effacement se régle avec
VR 111. Pendant l'enregistrement,
la sortie DIN est coupée du signal
moniteur avec le commutateur E-R S 1 — 5.
Indication de modulation
Commutateur réversible S 2
Commande de l'appareil