Revox A76 Service Manual

t F
matching
network
]
Test
generator
|
(for IF
filter
measurements)
“
1
coaxial
Push-on
terminal
BNC
cable RG
58
54.02.0327
^
Q_
O
™
I
lOn
max.
350
mm
4,7
k
alligator
clip
—
23
V
(blu)
from
distribution board
(not
required
with the
RF input
section 1,076.150)
Fig.
4Z-1
38
kHz
bandpass
(for subcarrier
minimum
adjustment)
15
kHz
lowpass
filter
(for AF
measureme
ts
f
=
15
kHz:
attenuation ma .
0.2 dB
f >19
kHz:
attenuat'on >
45 dB
Input
4,7
k
5
3
mH
34,4
mH 37,7
mH
Output
0
348
n
Fig.
4.2.-3
1,41
n
<
,
<
<
<
>
4,7
k
>
1,77
n
Tuner 60 H
Fig. 4.Z-2
Fig. 4.Z-4
4, ALIGNMENT
INSTRUCTIONS
4.1.
Test
equipment
For correct
alignment
the
following
test
equipment
(
or
equivalents)
will be
required:
Stereo
test
generator
Rohde &
Schwarz
type SMSF
BN
41410,
range 87
to
108
MHz
and
10.2
to
1 1.2
MHz
Stereo
modulator
Philips
PM
6450
Audio
generator
low
distortion
type
(THD less
than
0.05
%)
Digital counter
(for
38
kHz)
Oscilloscope
(with
internal
and
external
triggering) including
RF
probe
10:1
DC
transistor
or vacuum
tube
voltmeter
(
VTVM
)
including
RF probe
Multimeter
for supply
voltages
Distortion
analyser
(
or audio
millivoltmeter
with suitable
filters)
Note:
The
signal
voltage
indicated
for
the
stereo
test
generator is
an
open
circuit
voltage
(o.c.v.
).
If the
internal
impedance
of
the test
generator
equals
60
ohms,
a
voltage
of exactly 1/2
of
the test
generator's
open circuit
voltage will
result
accross the
60
ohm
input
of the
tuner (see
fig.
4.2.-4).
When
working
with
test
generators
whose
output
calibration
is already
taking
into
account the
nominal load
Impedance
of
the
equipment
under
test, the
generator's
output
is to be
set
to
one
half
of
the
Indicated
open circuit
voltage.
The
predominantly
used
test frequency
of
94
MHz
is to be
taken
as a
guide
only.
Prior to
starting
any
alignment
proce-
dures,
It should be
checked
whether
or not
that
frequency
does
not
produce
an
interference with a
neighbouring
FM
transmitter.
(This
should be
checked
with
the
test
generator
connected
to the
tuner, but
with the
signal
turned
off ).
If
an
FM
broadcast
can still be
received, the
test
frequency
should
be
altered
slightly.
The stereo
test
generator
is to
be
connected
to
the
60
ohm
antenna
input
for all tests (
except
for
the
tuning
steps 4.4
to
4.6
which
require
the test
frequency to be
fed via
the
IF
matching
network).
4.Z
Additional
tools
and
filters
All
readings
are to be
taken
against chassis.
One
set
of cables
(coaxial
cable
RG
58)
One
set
of
tuning
tools
The
following
filters
and
matching
networks are
required
for
I F
measurements,
subcarrier
minimum
adjustment
and
audio
frequency
measurements.
The
construction
of
these
circuits
is
not
critical.
IF matching
network
fig.
4.2.-1
( for
measurements
on the
IF
filters)
38
kHz
bandpass
fig.
4.2.-2
(
for
subcarrier
minimum
ad-
justment)
15
kHz lowpass
filter
fig.
4.Z-3
(for
audiofrequency
mea-
surements)
9

Revox A76 Specifications

General

Brand	Revox
Model	A76
Category	Tuner
Language	English