Revox B261 - Audio Section and Microcomputer Unit

STI]JDtrR
REVOX
8261 SA
sEcTtoN
3/5
3.6
AUDIO
SECTION
3.6.1
AUD]0
PCB r.726.820/82L
The two
AP signals
TL and
TR are
taken
through
the
strappable
for
US version)
de-emphasis
circuits
to
amplifiers.
The 400
Hz sinus
oscillator
can
be connected
with
switch
to
the
AF outputs
(FIXED
and
VARIABLE).
3.6.2
PHONES
PCB
L.'726.860
50
ps
(75
;rs,
the
output
a selector
The sockets
to the
front
panel
ancl the
corresponding
control-s
(OUTPUT
VARIABLE
and
HEADPI{ONES)
are
located
on
this
PCB'
The
stereo
headphones
amplifier
is located
on the
audio
PCB
L.726 .820
/
82t- .
AlI AF outputs
are
connected
through
relay
contacts
in
order to
eliminate
switching
clicks
when
the tuner
is
powered on
or
off.
3.7
MICROCOI"IPUTER
UNIT
The tuner
control
is
implemented
in this
functional
group.
The
heart of
thls
control
is a
mask-programmed
microcomputer
8440'
The
peripheral
circuj-ts
are
connected
to
this one-chip
microprocessor.
The CBUS
(data,
c1ock,
enable)
is controll-ed
by
the
bitlirectional,
serial
hardware
interface
of
the
microprocessor.
The
folfowing are
connected
to this
CBUS:
-
The 16-fold output
driver 5AA1061-2
on the
keyboard
PCB
(ICl).
-
The module SAA]057
on the synthesizer
PCB
(IC1).
-
The LCD driver
PCE
2111 on the
display
control
PCB
(ICl)'
-
The EAROI.{
ER 1400
wlth level- shifter
on the
microprocessor
PCB
(IC3).
The station
parameters
(frequency,
name,
mode)
are
stored
in this non-volatile
EAROF1.
-
The t6-fold output
driver SAAI061-3
on
the
microprocessor
PCB
(IC4).
The former
supplies the
control
signals
for the
antenna
switch
RFAB), stereo
decoder
(ST,ST-FI),
F!1 demodulator
(MUT)'
audio
PCB
(
CALOSC,
REL
)
,
power
supply
(
PSoN
)
,
comparator
circuit
(MC)
as
wel-l as the
mode signals
for the
EAROM
(IC3)
'
The
IR
remote
control
acts
on the
external
interrupt
input
of
the
microprocessor
through
the IR
preamplifier.
The comparator circuit
converts analog
signai-s
into control
signals that
can
be
processed
by the
pP. The signal
strength
signal
(SS)
is compared
with the voltages
of
the
potentj"ometers
threshold station
(PSTA)
and threshold
stereo
(PSTE)
and
converted into
the
di-gital control
signals
STA and
STE.
The
center
tuning signal
(CT)
is compared
with the
preset thresholds
and
converted
into the
pP
control signals
FL
and
FH-
The
meter
control
signal
(MC)
switches
off the signals
for the
signal
and
tuning
meters
during
the controJ.
processes
(SM
)TM)"
Through the electrically
insulated
PowER
ON
interface,
the tuner
can be swj-tched
on
(PON)
by the cassette
recorder
8710 or
through
an
external
timer contact.
The display
mode
selector
supplies
the signals
DI'41 and
DM2.
Other
input signals
for
the
pP
are supplied
by the
stereo
decoder
(P),
the
synthesizer
(CLCK),
as
weII as the
priority
encoder
on the
keyboard
PCB
(GS,
KB1.
. .3
)
.
on
tuners
that are
not
equipped wj-th
the optional "antenna
selector
A/8", the corresponding
front-pane1
control'
is
inhibited
(JAB).