Teac A-5500 - Page 34

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DOLBY
NR
FUNCTION
CHECK
DOLBY NR CHECK (1)
1.
Place
the
DOLBY
NR
switch
IN,
FM
COPY
switch
IN,
and
the
MONITOR
switch
to
SOURCE.
2.
Turn
the
FM
COPY
VR
(807,803)
on
the
back
panel
to
Maximum.
3.
Apply
a
100
Hz
signal
at
-48
dB
to
the
LINE
IN
jacks;
note
the
Output
reading
on
the
Test-Set.
4.
Change
the
input
frequency
to
5
kHz
(-48
dB).
The
Test-Set
indication
should
decline
by
10
dB
+0.25
dB.
5.
If
readings
are
not
within
limits,
recheck
and
adjust
DOLBY
ENCODER
PC
Board.
(Fig.
11-5)
NOTE:
The
following
checks
and
adjustments
must
be
performed
with
the
DOLBY
FM/COPY
switch
OUT.
DOLBY NR CHECK (2)
6.
Place
the
DOLBY
FM/COPY
switch
OUT,
DOLBY
NR
switch
OUT,
BIAS
and
EQ
switches
to
HIGH,
tape
SPEED
to
19
cm-7-1/2.
Thread
a
blank
low
noise/high
output
tape
on
the
deck.
. Record approx. 10 seconds of a 1 kHz signal at -28 dB and
a 10 kHz signal at -48 dB.
Rewind the tape, playback the recorded signals but
. while watching the Test-Set, set the DOLBY NR switch IN.
Comparing the outputs between DOLBY NR - OUT/IN, check
at 1 kHz for a decline of 5 dB +1 dB;
at 10 kHz for decline of 10 dB +1 dB.
12. If readings are not within limits, recheck and adjust DOLBY
DECODER PC Board. (Fig. 11-3)
DOLBY NR CHECK (3)
13,
Place
the
DOLBY
FM/COPY
switch
OUT,
DOLBY
NR
switch
IN.
BIAS
and
EQ switches
to
HIGH,
tape
SPEED
to
19
cm-7-1/2,
14.
Apply
signals
swept
from
40
Hz.22
kHz
at
-38
dB to
LINE
IN.
jacks
and
record.
15.
Change
the
tape
SPEED
switch
to the
9.5
cm-3-3/4
position.
16.
Apply
signals
swept
from
40
Hz
v14
kHz
at
-38
dB.
17.
Check
for
best
response.
No
further
adjustment
is
provided.
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Lt
20 50 100 200 5090 wo a aK 16K 15K 20K 30K 50K
Fig. 11-13 Dolby NR response Limits