Revox A76 Service Manual

L
205
P
301
Fig.
412.-1
Fig.
413.-1
412.
Alignment
of
FM
demodulator
Test
equipment:
Test
generator
frequency 94
MHz,
2
mV
o.c.v.
modulated
with
stereo
modulator,
deviation 75
kHz,
modulating
fre-
quency
1 kHz
(
L
=
R),
no pilot
frequency.
1
kHz ( L
=
R
)
no pilot frequency
15
kHz low pass
filter (see
fig.
4.2.-3)
Distortion analyser
VTVM
without
RF probe,
DC
range
412.
1 .
Power
switch
depressed,
tuning
pointer
set
to the
94
MHz
mark; fine tune
to
obtain
zero
indication
on
the
center
tuning
meter
( 44
)
set the
audio
output
controls
(55)
to
their maximum
setting
(fully
clockwise)
412. 2.
Connect 15
kHz
low pass
filter
between
the
tuner's
audio
output
(56)
and
distortion
analyser.
412
. 3
.
Measure
audio
output
voltage
with
the
distortion
analyser.
With
the
demodulator aligned,
the
audio
output
voltage
reads: 0.5
V (±0.1
V).
Maximum
permissible
level
difference
between
the two
audio outputs: 0.5
dB.
4.12.4.
Calibrate
distortion
analyser to
100
percent,
measure
dis-
tortion.
Adjust
IF
transformer
L205
to
obtain
minimum
di
tortlon
( see
fig.
4
12.-1
).
The
maximum
total
harmon
c
d'
tortion
with the
demodulator
aligned
must
not exceed 0.3
%.
412
5
*
CH r ; a resis
or
of
1
Mohm
to test
point
7
(
see
fig.4 12
-1
);
connect
VTVM (
DC)
to
that resistor.
4.12.6
Adjust
symmetry
potentiometer
P
301
(
see
fig.
4.12.
1
)
to
obtain a null
indication on
the
VTVM.
4.12.7.
Repeat
alignment steps
4.12.3.
to
4.12.6.
until
no further
improvement
can
be
reached.
413.
Alignment
of multipath
indicator
Test
equipment:
Test
generator, frequency
94
MHz,
2
mV
o.c.v.
modulated
with stereo
modulator, deviation
82.5
kHz,
modulating
frequency 1
kHz
(L= R),
no
pilot
frequency.
4.13.1.
Tuner:
Power switch depressed,
button
MULTIPATH
INDICATOR
depressed
(
Tuners
of the
MK II variety
are not
equipped
with the
button
MULTIPATH
INDICATOR)
Set
dial
pointer to 94
MHz
mark; fine tune
to
obtain
zero
indication on the
center tuning meter
(44).
4.13.2.
Adjust trim
potentiometer P601 ( see
fig.
4.13.-
1 )
until
the
light bulb
MULTIPATH
(42)
becomes
Illuminated;
then
turn
back
P601 to the
point where the
light just goes
off.
14

Revox A76 Specifications

General

Brand	Revox
Model	A76
Category	Tuner
Language	English