Revox B261 Serviceanleitung Seite 40

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).