Marantz 4270 - Dolby FM Preset Level Controls Alignment

3. For the level adjustment, set the DOLBY switch and SELECTOR switch to the RECORD |
and CD-4/AUX positions, respectively, and use the TAPE MONITOR OUT jack for the
signal
output.
By
setting
the
400Hz
TONE
pushswitch
“in’’,
the
400Hz
sine
wave
is
fed
out.
Adjust
the
semi-fixed
resistor
RL11
for
580mV
of
the
sine
wave
output
voltage
in
both
R
and L channels. Then, set the DOLBY switch to the RECORD II position, and apply the
400Hz signal for 580mV of the output voltage. Adjust the semi-fixed resistors RL28 and
RL29 so that the DOLBY LEVEL meter may point the Dolby level. Change over the METER
switch, and perform this adjustment for both R and L channels.
Next, adjust the semi-fixed resistor RL12 for 580mV output level when the DOLBY switch is
set to the OFF position. Check the 400Hz output signal level after the adjustment of the level
setting semi-fixed resistors RL11 and RL12. The output level must be precisely 580mV since
it is a reference level of the Dolby circuit.
23.
ALIGNMENT
PROCEDURES
OF
DOLBY
FM
PRESET
LEVEL
CONTROLS
Connect
an
FM
signal
generator
to
the
FM
antenna.
Set
the
signal
generator
for 400Hz
and
50%
modulation.
Set
the
FM signal
generator
to
98MHz
and
the
DOLBY
switch
to
the
OFF
position.
Turn
the
Tuning
knob
on
Model
4270
until
it
tunes
to
the
98MHz
signal
from
the
FM signal
generator.
Then,
set
the
DOLBY
switch
to
the
DOLBY
FM
position,
and
adjust
the
FM
preset
level
controls
RCO5
and
RCO6
so
that
the
DOLBY
LEVEL
meter
may
point
the
Dolby
level.
Change
over
the
METER
switch,
and
perform
this
adjustment
for
both
R
and
L
channels.
24. EXPLANATION OF THE DOLBY PROCESSING CHART
This chart shows the condition of the signals available at the speakers (SPKRS) and at the
TAPE MONITOR OUT terminals as a function of different control settings.
To understand the chart refer to the symbols below:
— Represents a signal which has not been applied to either Record or
———— Playback Dolby circuits. The relative amplitudes of all audio frequ-
encies remain unaltered at all levels.
— Represents’a signal which has been processed by the Dolby Record
/ circuit. The relative amplitude of the high frequencies is increased at
low signal levels.
— Represents a signal which has been processed by the Dolby Playback
\ circuit. The relative amplitude of the high frequencies is decreased at
i low signal levels.
-— Represents a signal which has been processed by both the Record and
the Playback Dolby circuits.
These circuits are complementary. Therefore, relative amplitudes of all audio frequencies are
restored to their original values.
12