Orban 424A Operating Manual page 30

8)
OPTIONAL
verification of
LIN and
EXP
release
a)
Connect
the vertical input of
a storage scope
to
the rear-panel
STEREO
COUPLE
terminal. This monitors the gain of the
VCA,
and
is
scaled such that
each dB
of gain reduction
changes
the voltage by -0.4V.
b)
Operate
the
scope
at
IV/div
vertical
and approximately 0.2sec/div
horizontal.
Switch
the
RELEASE SHAPE
switch
to
LIN and make
sure that the
GATE THRESH
is
OFF. Apply
a level
from
the oscillator to the
424A
input
terminals
sufficient to
make
the
424A
G/R
meter
read "20dB". This should
produce
a voltage
at
the
STEREO COUPLE
terminal of
approximately
-8.0V.
c)
Suppress the
oscillator output,
and observe the control voltage with the scope
as
it
releases.
It
should create a
straight
line until
-0.3V has been reached,
at
which
point the
line will
become much more
horizontal.
Do
not
erase
the
trace;
it
will
be superimposed with another trace
in
the next
step.
d)
Switch
the
RELEASE
SHAPE
switch to
EXP. Restore
the
oscillator
and
verify
that
the
G/R meter
once
again
reads "20dB". Suppress
the
oscillator
and
superimpose
the control voltage
release shape upon
the
LIN
shape
measured
in
step
(c)
above.
When
superimposed, the two
traces should look
like
Fig. D-3.
OdB
VCA
GAIN
-20dB
TIME—
Fig. D-3: LIN
and
EXP
Release Shapes
26