Dual C 844 Serviceanleitung Seite 7

G
The dynamic HIGH
pulses
produced
by Pin
14
to
Pin
20 (lC
4Og)are
converted
to
static HIGH
signals
by the D-latch lC 408. The informa-
tion
pending
at
the
D
input
is
written into the clock input Pin 9
(lC
4O8) by a HIGH pulse
(approximately
10 |ls)
and is available in static
form at the O
output until
new information
is
stored.
Captan motor, reel motor
With
a
HIGH signal
from the processor
(lC 409, Pin
16),
which isstored
in
the D-latch lC 408,
O
403
causes
the transistor Q
402
to
become
forward-biased and
this
applies
the operating
voltage
of
- 16
V to
the
Capstan motor and
reel
motor, connector
A (board C)
Pin
10.
The
refe-
rence voltage
for
the
tape
speed
is set
with
VR 403
(9.5 cm/s)
and
Vn
4O2
(4.75 cm/s). The phototransistor
in
lC 411
is always
forward-
biased and
only functions
when
the
rewind
speed REW
is regulated.
The
f
lywheel
of
the
Capstan
drive
is implied via an
intermediate
linkage
for the FF or
REW
function. ln
order
to
prevent
excessive stressing
of
the tape at the end
of
the
reel,
*
during the
function
REPEAT
=
REW
and
9.5 cm/s
-
the rewinding
speed
is
slowed
down
towards the end
of
the
reel via
the
optocoupler lC
41
1. The signals
of
the tape run
sensor
lC 412
are evaluated
by
the
processor. lf
the pulse frequency
rises abo-
ve
J5 Hz,
LOW active regulation pulses
are routed
from
Pin
33 (lC
409)
through D 415 to the inverter
lC 406, Pin 2. The HIGH pulses from
the
output Pin
15
control the photodiode
in
the optocoupler
lC 41
1.
With
each
positive
pulse, the
integrated
phototransistor
becomes
reverse-bia-
sed
and
increases
the reference voltage via
R
465.
The Capstan motor
is
slowed
down
accordingly.
ln
order
to
ensure
that the
tape
reaches
a
high rewinding
speed
in FF
mode,
this
regulation
function
is
cancelled
by a HIGH
signal via D 414
and
the
phototransistor
is
forward-biased.
Mnsic
finder
lf
the buttons FF
or
REW are operated during
the play function,
the
processor
recognizes
the
music finder
function
and routes a LOW
signal
= SCAN
to
Pin
3i
(lC
4Og). This signal
is
routed
to
transistor
A
414 in
order
to
enable
the finder
amplifier. The
magnets
FF
and
MF (music
finder)
are
energized
and,
in
this way, the
double-head
only just
tou-
ches
the tape
in
order
to
guarantee
reliable recognition
of the
music
gap. Wear
of
the
audio head is reduced
to
a
minimum, thanks
to
this
bare
touching.
lf
a music gap is now recognized
(SPACE
=
LOW active,
see
also analog section),
this
LOW
signal
is
routed
to
the processor in-
put
Pin 38 which
initiates
the play
f
unction.
Auto-space
When
the
AUTO
SPACE
button
is operated
during
RECORD mode,
the recording amplifier
is
muted
*
HIGH
signal f
rom Pin
32 (lC
4Og) to
O 419
-
and
the tape
runs approximately 4 s more
until
the
processor
stops
the tape
and triggers
off
RECORD
STANDBY.
With
the
com-
mand PAUSE
(HIGH
active Pin
2O
of
lC 4Og), Q
419
becomes reverse-
biased =
clear
muting playback by a LOWsignal via
lC 408 and;nverter
rc
406.
Record standby
lf the
button
RECORD
is
operated and
the
contact
RECORD
SAFETY S 13
is
closed (LOW at Pin
36,
lC
409), the deck
changes
over
to
the
function RECORD STANDBY which is indicated by flashing
of
the
green
LED
PLAY. The
magnet
PLAY
is energized,
muting
of
the
playback branch
is
cancelled (clear muting playback), the
Capstan
mo-
tor
is
switched on, the
recording
amplifier isenabled
(clear
muting
RA,
O 4i9<everse-biased),
the
LED
PLAY
flashes and
the
LED
RECORD
lights
up.
lf
the button PLAY
is now operated,
the deck
changes
over
to the
record
function.
LED display
The
funJtions
STOP,
PLAY, RECORD, REPEAT and DOUBLE SPEED
(9.5 cm/s)
are each
indicated
by
one LED.
With the
exception of
DOUBLE
SPEED,
the
LED's
are
driven on
theircathode sideswith the
LOW active decade pulses
(inverter
lC
406). The positive operating vol-
tage is connected
as
pulses with the transistors
O
416
and
Q
417.
lf,Ior
example,
the
LED
RECORD
is
activated,
the processor produces the
activation pulses
for
O
416 in phae with
the pulses of
decade
2.
lf
,
on
the
other
hand,
the LED
REPEAT
is
to
light up, the activation pulses
lor Q
416
are
synchronous
with the pulses of
decade
4.
Counter
The 4-digit display
is
driven
in multiplex
mode vla inverter
lC 4O6
{de-
cade pulses LOW
aktive) and inverter lC
407 (segment
pulses
LOW
ac-
tive).
Display
of
the dots
for
MEMORY
and SET
is
controlled by O 416
and
A
41'7
.
Pulse Diagramm lC 409
T=12ms
t =
3ms
Dek.
1
Dek.
2
Dek.
3
Dek. 4
Record Switch
Memory
Switch
Pause
Switch
O
416 LED
Rec.
O
416 LED
Rep
O
416 LED
Rec.
+
Rep.
3 6
I
1215 182124 t(ms)
Remote control
The lR
signals converted to electrical
pulses by the infrared
receiver
are
routed via
C
413
and
inverter
lC 4Ob Pins 11110
and Pins
9/8 to the
in-
put
Pin 35 of the processor lC
4O9.
Cause
of
the
signals:
A
coded command
consists
of
16 bits. As
each
transmitted command is
repeated
for
increased
reliability,
commands
consist
of
2
x
16
bits=
96
ms
duration.
One
bitcorresponds to
a length
of
3
ms
and isclocked with
a
frequency of
approximately 28.5
kHz.
Point
A:
The clocked
bits
are applied
as
voltage fading.
Point
B:
The
signals are differentiated and limited to 5 V with
C 413
and
R
456
(diodes
D 411
and
D 412\.
Point
C:
The pulses are negated
by the inverter lC 405. Positive
needle
pulses are
now applied.
Point
D:
The
pulses are
integrated
by
R
454
and
C
412.
Point
E:
lnverter lC 405
negates and
a positive
pulse
=
1
bit
with
a
duration
of
approximately 3
ms
is
applied
ar
the input
of
the
processo r.
Thls
method
ensures
good
suppression
of
noise
pulses.
Points A
to
E
are
identical
with
the designations in the circuit
diaqram.
5V
B
ou
5V
C
ov
5V
D
ou
E L
OV
6)
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