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Moog Satellite Service Manual

Moog Satellite
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Page #15 background image
iC15
determines
the
bandwidth
(Q)
.
These
gains
are
set
by
the
..bias
currents
which
are
fed
from
transistor
pairs
Q39-40
and
Q37-33
respectively-.
These
transistor
pairs
aray
be
compared
directly
to
the
transistor
pair
in
IC11
which
determines
the
frequency
of
oscillation.
The
main
difference
is
that
relatively
constant
currents
are
fed
to
these
transistor
pairs
through
R133
and
R129.
A
precise,
wide
range
relationship
between
output
current
and
base-to-base
voltage
is
not
required
of
these
transistor
pairs.
Only
reasonable
repeatability
and
the
rough
approximation
of
exponential
characteristics
are
needed.
'
The
bandv/idth
is
determined
by
the
voltage
difference
between
the
bases
of
Q37
and
Q33.
The
voltage
at
the
base
of
Q37
is
the
result
of
the
bandwidth
control
currents
flowing
through
R128.
An
increase
of
18.5
mv
doubles
the
bandv/idth.
There
are
two
sources
of
Bandv/idth
control
current:
Row
£8
of
the
resistor
matrix,
and
the
EMPHASIS
potentiometer
voltage
applied
to
R121.
The
Center
Frequency
is
determined
by
the
voltage
difference
between
the
bases
of
039
and
Q40.
The
voltage
at
the
base
of
Q40
is
the
result
of
the
center
frequency
control
currents
flowing
through
R134.
An
increase
of
18.5
mv
doubles
the
center
frequency..
These
currents
come
from
Row
i-7
of
the
resistor
matrix,
the
COLOR
potentiometer
voltage
applied
to
P.193,
the
EXTERNAL
jack
voltage
applied
to
R184,
the
modulation
voltage
applied
to
R181,
the
filter
contour
voltage
applied
to
R116,
and
the
keyboard
pitch
voltage
applied
through
R179
and
R180.
The
current
from
row
54
of
the
resistor
matrix
determines
whether
or
not
Q25
conducts.
When
Q25
conducts,
it
is
saturated
and
shorts
out
the
keyboard
voltage
which
is
routed
to
control
the
center
frequency.
R130
and
R132
are
offset
adjustments
for
setting
correct
values
of
bandv/idth
and
center
frequency
respectively.
They
compensate
for
transistor
offset
voltages,
resistor
variations,
and
gain
variations
of
IC15,
IC16,
and
IC17.
The
output
of
the
bandpass
filter
is
taken
from
the
source
of
Q41
and
applied
across
the
bases
of
the
bottom
transistor
pair
of
IC19.
This
transistor
pair
and
the
two
immediately
above
it
consitute
a
low
pass
filter
whose
cutoff
frequency
is
proportional
to
the
standing
current.
This
current
is
in
turn
determined
by
the
voltage
difference
between
pin
13
of
IC19
and
the
base
of
Q33.
The
voltage
at
the
base
of
Q33
is
the
result
of
cutoff
frequency
currents
flowing
through
R151.
These
currents
come
from
row
#9
of
the
resistor
matrix,
the
COLOR
potentiometer
voltage
applied
to
R186,
the
EXTERNAL
jack
voltage
applied
to
R185,
the
modulation
voltage
applied
to
R187,
and
the
filter
contour
voltage
applied
through
R117.
The
setting
of
R139
determines
the
calibration
current
through
R140.
An
increase
of
approximately
18.5
millivolts
at
the
base
of
Q33
results
in
a
one
octave
increase
in
the
cutoff
frequency
of
^
the
low
pass
filter.
‘

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Moog Satellite Specifications

General IconGeneral
BrandMoog
ModelSatellite
CategorySynthesizer
LanguageEnglish

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