Revox A76 Service Manual

VTVM
L 106
VTVM
Fig.
4.7.-3
4.
8
=
Alignment
of
IF
amplifier
(
Adjustment
of
transformer
coupling.
For
alignment
in-
structions
pertaining
to the
I
F
filters,
see 4.4.)
Test
equipment:
Test
generator,
frequency
94
MHz,
2
juV
o.c.v.
no mo-
dulation
VTVM with
RF probe,
range
to
read 0.5
V
approx.
4.8.1.
Tuner:
Power switch
depressed
Move
pointer
to
the 94
MHz
mark
and
tune to
obtain
exact
zero
indication
on the
centre
tuning
meter
(44).
4.8.2.
Connect
RF
probe
of
VTVM
to
test
point
6
(see
fig.
4.8.-1.)
4.8.3.
Connect
test
generator to
the
tuner's 60
ohm
input ( BNC/59
)
4.8.4.
Adjust
IF
transformers L201
to
L204
to
obtain
maximum
reading
(
VTVM
reading 0.5
V
approx. ).
During
this test,
no
limiting must
take place
in
1C 204.
(This
can
be
checked
by
slightly
increasing
the
output
level
of
the
test
generator
which must
cause
a
corresponding
rise
of the
signal as
indi-
cated
on the
VTVM.
If
limiting
does
occur the
output
level
of
the
test
generator must be
reduced).
4.9.
Checking
symmetry
of
the center
tuning
meter
(44)
Optimal pointer
deviation
—am
0
1
1
maximum
permissible correction
Fig. 4.9.-1
Fig.
4.8.-1
4.9.1.
Use
same
test
generator
setting as
under 4.8.
4.9.2.
Turn
tuning
knob
( 40
)
slowly
cw
and ccw
to
detune
while
observing
the
pointer
for symmetrical
movement (
see
fig.
4.9.
-1
)
4.9.3.
A
symmetry
error
not
exceeding
one
quarter
of the
width
of the
"zero
zone"
is to be
corrected with
the
secondary slug
of the
center
tuning
discriminator
FT 601.
See
section
4.5.6.
and
fig.
4.5.-1.
4.10.
Checking
for correct
limiting
(IF
amplifier)
4.10.1.
Use
same
test
generator
settings
as
under 4.8.
4.10.2.
RF
probe
of VTVM
remains
connected
to test
point
6
(see
section
4.8.2.
)
4.10.3.
I
ncrease
output
level
of
test
generator gradually.
When
raising
the
output
level
above
4
piV o.c.v., the
voltage
level
as
indica-
ted
by
the
VTVM
must
not
increase any
more.
(
Limiting
taking
effect).
4.11.
Sensitivity
check
on the
center tuning
(
44
)
and
the
signal
strength
meters
(43)
4.11.1.
I
ncrease
output
level
of
the
test
generator to 10
mV
( no
modulation)
4.11.2.
When
running the
tuning
control
(40)
through
its
full
range
with
this signal
present at
the
tuner's
input,
the
following
meter
indications must
be
obtained:
Center
tuning
(44)
from
±
2
to
end
of scale
Signal
strenght
(43)
from
5
to end
of scale
13

Revox A76 Specifications

General

Brand	Revox
Model	A76
Category	Tuner
Language	English