Fig. D-l: IOOHZ
DISTORTION RESIDUAL,
LIN
RELEASE
c) Restore the oscillator output.
Switch the
RELEASE SHAPE switch to EXP,
and verify that
the
distortion decreases, and that the distortion residual looks
like Fig.
D-2.
Suppress the oscillator output, and
verify
that the time
required
for the
G/R
meter to move
from
20dB to lOdB G/R is
2.0seconds,
+0.5seconds.
Fig.
D-2:
IOOHZ DISTORTION
RESIDUAL,
EXP
RELEASE
NOTE
The shape of the
distortion
residual
provides
a good indication of
whether the
timing module
and
other circuitry within
the
control
loop are
operating properly. If the distortion residual which you
observe is significantly different
than the
Figures (particularly if
accompanied
by audible
problems
with sound quality), we recommend
returning the
424A for
factory service,
as
it is usually impractical
to
diagnose
and repair subtle
control
circuitry problems in the field.
5)
COMPRESSION RATIO control test
a)
Set
the
424A ATTACK TIME control
to
"0"
(FAST), and the RATIO control
to
"infinity". Set
the oscillator frequency
to
IkHz, and
its output
to produce
lOdB
G/R.
Adjust the OUTPUT
TRIM
control
as
necessary to produce
+ II.OdBm at the
424A
output.
(The
OUTPUT
TRIM control
should
be within
2dB
of
"0"
after you have done this.)
b)
Set
the RATIO control at each
of
the
panel markings
in TABLE D-l,
and
verify
that the 424A
output
level
is close to the values
indicated,
+ldB.
24
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