Revox B150 Service Manual

STUDER R^OX
B250/B250-S/B150
E3/3
Seixsiti
The
INPUT
L/R
signals
from
the
INPUT-OUTPUT
UNIT
are
added by
the
opamp
(5)
and
converted
to a
DC
voltage
by
a
peak
responding
rectifier
(6).
This
voltage
is
subsequently
evaluated
by
the
microcomputer
(1)
via
the
comparator (7),
by
varying
the
reference
voltage
via
the
DA
converter
(8)
until
the
latter
responds.
The
detected
input
voltage
is
now
compared
with
the
stored
NOMINAL
SENSITIVITY
of
550
mV
and the
difference
is
stored
in
the
EEPROM.
When
the
source
is
changed
over
the
volume
controller
is
readjusted
in
accordance
with
the
stored
difference-
Heat
and DC
m
onit
o
ring.
The
amplifier
is
equipped
with
three
temperature
sensors
<NTC3
for
PWR L,
PWR R,
and
the
transformer.
They
are
connected
to
the
comparator
(9).
Monitoring
consists
of
3
phases.
The
first
threshold
is
reached
when
one
of
the
three
monitoring
voltages
exceeds
2.0
V. As
a
first
response
the
volume
is
lowered
by
iO dB.
The
symbol
««<)
appears
on
the
display.
The
second
threshold
is
at
2.7
V.
This
means that
the
transformer
or
one
of
the
output
stages
is
overheated
aOO°C).
The
wording
(OVERLOAD
! !
!>
appears
on
the
display
and
the
relays
(Section
3.1:
26,
27,
28,
29)
drop
out
immediately.
The
third
threshold
is
attained
at
4.5 V.
This
means
that a
DC
voltage
is
available
on
the
PWR
OUTPUTS.
This
can
be
detected
by
connecting
the
outputs
PWR
L/R
to
two
low-passes
(10,
11)
and
by
converting
the
signals by
means
of a
negative
and
a
positive
peak
detector
(12,
13) to
a DC.
The
result
is taken
via
an OR
gate
(14) to
the
monitoring
input
of the
microcomputer.
The
latter
detects
that
the
highest
threshold
has
been
reached.
It
immediately
deenergizes
the
output
relays
and
the
wording
(BREAKDOWN !
! !)
is
displayed.
The
COVER
signal
indicates
whether
the
hinged
cover
is open
or
closed.
When
the
cover
is
closed
the
microcomputer
cancels
any
programming
operation
that
has
not
been
completed
yet.
The
COVER
signal
also
has the
effect
that
the
LCD
backlighting
is
switched
off.
The
communication
between
the two
microcomputers
is
based
on
the
so-called
handshake
process
via the
lines
DATl,
CKll,
CK12.
The
clock
pulse
is
supplied
to
the
microcomputer
(1) via
a
driver
from the
4.9152
MHz
quartz
oscillator
of
the
microcomputer
(2).
12.)_
The
microcomputer
(2)
operates
in
one—
chip
mode,
i.e.
its
inputs
and
outputs
are
connected
as
ports.
After
each
RESET
the
microcomputer
must
be
restored
to the
correct
mode.
This is
accomplished
via
the
ports
P20, F21,
P22,
Ports
P21
and
P22
are
connected
to high
via
resistors. P20
receives a
"high"
from the
reset IC
via an
OR
gate
(15).
Via
the
various
ports it
reads
the
keyboard
matrix
(16)
comprising
29
push
button,
and
also
controls
the
fluorescence
display
(17).
It
also
controls
the
data
traffic
via the
serial
link
and
receives
the IR
signals.
When
the
amplifier
is
switched to
STAND
BY
mode
the
microcomputer
(2)
shuts
down the
power
supply
with
the
POPE
signal.
Seri al
link
The
data
flow
between
the
controller
and
the
microcomputer
is
routed
via a
6—
pin
DIN
socket
and
an
optocoLipler
(21).
The
IR
input
can
be
disabled
by
means
of an
optocoupler
.
This
is
accomplished
by
returning
the
supply
voltage
from
the
controller
to
the
Serial
Link
socket
where
the
line
after
the IR
preamp
is
interrupted
by
the
optocoupler
(21)
with
the
switch
(22).
The
DOTS
drivers
(18)
are
loaded
serially
with
10-bit
data
via
four
parallel
port
lines.
The
microcomputer
supplies
a
blanking
pulse
via
the
monoflop
(19).
During
this
blanking
interval
for
the
next
digit
the
BRIDs
drivers
(20)
switch,
and
the
corresponding
data
are
read
from
the
DOTs
drivers.
The
individual
digits
are
changed
over
with a
frequency
of 2
kHz.
For
the
individual
digits
this
results
in
a
multiplex
frequency
of
100
Hz. An
LDR
(as
sensor
for
the
brightness
of
the
ambient
light)
varies
the
duration
of
the
dark
interval
which
in
turn
influences
the
brightness
of the
display.
3.^
POWER
TRANSFORMER
B250/B25
0-S
The
power
supply
consists
of a
transformer
equipped
with a
switch
for
selecting
the
line
voltage
between
lOO
and
240
VAC.
On
the
secondary
side
it
has six
windings:
one
for
±16
V
with
center
tap,
one
for
VVFD
(+33V),
one
for
+5 V,
and
one
with
center
tap
for
heating
the
vacuum
fluorescent
display.
This
heating
is
interrupted
in
STANDBY
MODE
by
an
electronic
switch.
The
center
tap is
biased
with 6
VDC.
For
the
two
POWER
AMPLIFIERS
L/R
there
is one
winding
each
with a
center
tap
of
42
VAC
plus
a
supplementary
winding
of
53 VAC.
The
power
supply
is
controlled
via
the
POFF
signal.
It
directly
switches
the
VVFD
and
the
+16 V
voltage.
The
regulators
for
—16
V
and
the
heater
switch
are
controlled
by
the
+16
V.
The
+5
V
are
available
also
in
STANDBY
mode
(to
supply
the
microcomputer).
B150
The
power
transformer
is
available
in
three
different
versions
for
110 V,
220 V,
and
240
V
AC
supply.
In
place
of the
thermal
sensor
found
in
the
B250/B250—
S
there
is
a
thermal
switch
(120°C)
on
the
primary
side.

Revox B150 Specifications

General

Brand	Revox
Model	B150
Category	Amplifier
Language	English