Dual C 844 Serviceanleitung Seite 6

amp)
is act;ve HIGH and is routed
f
rom the
device
control
via connec-
tor C
(board
A)
Pin 2
to
O 602 which
connects
the input
ofthe
recor-
ding
amplifier
lC 602
to 0
V via O 508.
Also
during
recording and when
AUTO
SPACE is operated, this control
signal
creates
the
music
space
lasting approximately 4
s.
Muting
of LINE
OUT
and
MONITOR
is realized
by the
forward-bias of
transistor
O
27
1 (HIGH
signal at
the
base).
The
processor routes the
control signal MUTING playback to
board A,
connector C. Pin
5
as
a
LOW active
signal
during the following functions: stop, rewind, fast for-
ward,
music
finder ))
and
{{
and
pause.
DIN output
switched
off
= relay
RY
1
idle,
the contacts
are
open, tran-
sistor
O 355
is
reverse-biased, as
O 354
becomes
forward-biased due
to
the
RECORD command (H
IGH active).
CLEAR
MUTING playback = enabling
of
muting during the following
functions: plaV,
record
SB
(standby)
and record. The control
signal
CLEAR
MUTING playback
(HIGH
active) produced
by rhe processor
is routed through connector C (board
A)
Pin 5
to
lC 603, the output
Pin
10
of
which
changes
to
HIGH
with
a
delay
(C
601)
and
transistor
Q
351
becomes
forward-biased. Due
to
AND gating with
O 3b2, the
muting transistor
()
27
1
cannot
become reverse-biased via O 353 until
O 352
is forward-biased.
A
352
is always forward-biased when
the vol-
tage
of the power supply
unit
is
at
its
correct
level,
H
IGH signal at con-
nector C
(board
A)
Pin
7.
The
output pin
1l of
lC 603
applies a HIGH
level
to
the
base
of
O 352" This control
signal
is
also routed
to
the
base
of O
355,
this
becornes
forward-biased
and switches on
the
relay
and
the DIN output
is
connected
into
rhe
AF
signal.
If the
RECORD com-
mand
is issued
(HIGH
active),
O
354
becomes forward-biased and thus
renders O
355
reverse biased.
The DIN output js
disconnected.
Recording
levd
indications
VU: The
LINE
OUT output
signal
is
amplifled
with
the
display ampli-
fier Q2'73 viaR
284 and routed
to
the
VU
meter via the
f
ull
wave recti-
f
ier. The
full
wave rectif
ier ensures
a
precise indication
and
the VU
me
ter operates
with
damped return.
VU
is set
for
the 0 dB reference
level
with
VR
27
1. The transistor
O
274 mutes the
instrument
during
all
LINE
OUT muting functions.
Peak ievel:
The
tape type-dependent
and
treble
equalized signal is de-
coupled
from
the
output of the
recording
amplif
ier lC 602
Pin
4 wlth
C
545
and
routed via the control VR
503
to the
inpu r Pin 2 of the inte-
grated
display amplifier lC 605 which directly
drives
the
LED's
with
its
outputs. With transistor
O 507 (forward-biased),
the sensitivity
is
swit-
ched over
when the
tape type
selector
switch
S
2'l -3
is set
to
MET. The
dispiay
is inertialess
with 5
LED's which indicate the
magnetization
of
the tape
as a
percentage.
Device
control
Processor
All
devlce and
drlve functions
are
controlled by
a
4-bit microcomputer
wlth
integrated
2
kbyte program memory. The clock frequency is
ap-
proximately 500 kHz with
CF
401 at
Pins
24
ancl
25
of
the processor
tc
409.
Reset
When
the deck
is
switched on, the supply
voltages stabilize to
their
no,
minal
values.
With this
LOW-HIGH
edge
at the
reset
input Pin 23
of
lC
409, the
program
counter
of
the precessor
issetto
itsstart
address and
the processor
is eqabled
for
its
functional
sequences.
Via
D
418
and
C
411
, aclear pulse'is routed
to the
D
f
lipf
lop
lC
408 Pin
1.
lnputs
The
drive and memory control buttons
are
interrogated
and
processed
by
the
processor in,the {orm
of
a
clocked switch
matrix.
The
positive
pulses
of
lC 409 produced at
Pin
7
(decade
2)
to
Pin
9 (decade4),
which are lnverted
with
lC 406,
serve as
the working
clocks. These
pulses
have
a mutual oFfset
of 3
ms
(see pulse diagram). When
a
drive
control
button
is
operated, the signal
is
applied
as
a
HIGH
active
pulse
(inverter
lC
405) to the
processor
lC
409.
The contact
sensor
S
'13
RECORD SAFETY
(erasure
block)
is
open
when
a
musicassette is inserted =
H
IGH signal. ln this
case,
the proces-
sor ignores
operation of the
R
ECORD button.
The
timer switch S 1
routes
its inputs PLAY
or
REC as LOW active
signals
to
the processor.
DLL
The
no-contact
infrared light
barrier system
is
applied.
The
infrared
emitter
LED
406
is
driven
by the free oscillating oscillator
lC 4O4
f
rom
Pin
1
vla O
415.
The
clock frequency
is 1050 Hz and
can be
varied
with
VR 401. This frequency
is also routed
to
Pin22of
the processor
as
the
reference
frequency (see
also end
of
tape switch-off). This
clocking
principle
ensures
perfect
resistänce
to
constant light
and
interfering
re-
flections. The light pulses
are converted
to electrical pulses
by the pho-
totransistor O 42O
and these are
processed
by the comparator
lC 404.
lf
the light
barrier
is
obstructed
(DLL
ON),
a
wave-shaped HIGH
level
is
applied
to
the
output oI
lC
4O4
Pin 7 for
the duration
of the obstruc-
tion
and
this
is
converted
to
LOW level
with
R 443,
C
41.l
and D 410.
This
LOW signal also occurs when the
cassette sensor
S
12 is
closed
(cassette removed). Due
to the
[*OW signal at Pin 41
(lC 409), the pro-
cessor recognizes
DLL
ON =
cassette removed. The stop {unction
is
executed,
the LED
STOP
f lashes
and,
in
recording mode, the RECORD
function
is cancelled. When the deck
is set
to
PLAY,
this operating
sta-
te
is
stored after removal
of
the
cassette
End of
tape
switch-off
The information that the
tape
is
running is passed on
to
lC
412 by
a
multiple
magnetic disc secured
to the
drive wheel
of the
take-up wheel.
This lC
converts
the
alternating magnetic fields
into
electrical
pulses.
These pulses are routed through
C 414
to transistor
O 418
which
opera-
tes
as a f lipf
lop together
with
IC 406
Pins -/110.
The
signals
shaped in
this
way
are routed
through
R
457
to
Pin
37
of
lC
409" This
tape-run-
ning
frequency is compared
by
the processor
with the
1050
Hz fre-
quency of
the oscillator lC 404which isapplied
IoPin22 (|C409). lf
the
lape-running pulses fail within
a
period
of
1 s,
e.g.
due
to atape jam,
STOP is triggered
off.
ln
the
event
of
tape-running malfunctions,
the
1050 Hz (+ 5
%)
frequency
should
also
bechecked,
asthisservesasthe
reference
frequency
for
switching
off
at the end
of
the
tape.
Outputs
The outputs
for
the
device
functions
(magnets
and motors)
are
issued
by the processor
as
H
IGH
active signals.
The
course
of
the
signals
{or
FF
(fast
forward)is
used here
as
an
exarnple. The active HIGH
signal
of
the processor {Pin 10, lC 409) is routed
to
both
the
inverting drlver
lC
4O2,
Pin
1, and
to the
NAND gate
|C410,
Pin 9. Wirhthe
LOWsig-
nal at the output
of
iC
4O2,Pin
16.
transistor
O 412 becomesforward-
biased and applies
the positive voltage
of
approximatelV
6 V to the FF
magnet.
At
the
same
time, the processor
(lC 409, Pin
19 = U BAT)
sto-
res
the overexcitation
signal
in the D
latch iC 408 Pin 6 for
the dura-
tion of
approximately
100
ms.
This time signal
(HIGH
active)
is
routed
from
the
output
Pin
7
to
the NAND
inputs
of
lC 410.
The FF
com-
mand
is applied
as a
HIGH
signal
to
Pin 9
of
lC
410. Fortheduration
of the time
signal
(100
ms)
at Pin 8,
the
output
Pin
i0
changesto LOW,
lhe inverting driver lC 402
causes
transistor
O
409 to
become
forward-
biased
with
HIGH
and
drives
the driver stage lC
401 Pin
1
1.
Via
Pin
10.
lC 401
applies
the
overexcitation voltage
of - i6
V to
rhe FF
magnet.
After the time
signal
U
BAT
(100
ms)
has
elapsed, the
diode D 404
holds the
maqnet
until
O 412
switches
off.
This overexcltation
ensures
rapid and reliable
response
of
the
magnets. Repeated overexcitationof
magnets
already switched on
is suppressed
with
the coupling
diodes
D
419
to
D 424.
Example:
The
LOW signal
FF
at
the output
Pin
10
(lC 410)
is routed vta
D
423
10
the AND input Pin
1
and thus
disables
overexcitation oI the
magnet
PLAY which
is
being held.
rc
409
Prozessor
-\
1
tc
402
lC
410
Solenoid
FF