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5.3.3
GR METER ZERO AND TRACKING
Depress the GR meter pushbutton.
Disable limiting by turning
the Attack control full CCW to the detented OFF position.
Adjust
the meters to read
0
VU with trimpot
R61 for
Channel
A,
and R161 for
Channel
B.
Apply
a
1
kHz,
0
dBm input signal and adjust
for
5
dB of
limiting
as
described
in the
previous paragraph.
Set the Output
control
so
that the meter, switched to
+4,
reads
0
VU with no limit-
ing and -5 VU
with
5
dB of limiting.
Switch the meter back to GR
and adjust the GR
Tracking control R65
(R165) to
give
a
-5 VU
reading when the unit
is in
limiting, and the Meter Zero pot
R61
(R161) to
give
a 0
VU reading
when
no limiting
is
taking place.
5.3.4
COMMON MODE REJECTION
The trimpot
R1
(RlOl) is
used to adjust for
maximum common
mode rejection.
Set the controls as follows:
Input
Output
Attack
Release
Compression Ratio
Meter Mode
to number
"18"
on the front panel
full CW
full CCW (switched to OFF position)
full CW
20:1
GR
Apply
a
signal to the input
(100 Hz,
-10
dB)
.
Adjust
the Input
Level control to achieve +10 dB output level, measured with an
external AC voltmeter.
Connect the
"±"
and COM terminals together
and feed
a
signal of the same input level to this
connection
and to
the
GND terminal
of the
limiter input.
Measure
the output signal
level, and
adjust
R1
for
a
minimum
reading, switching the external
meter
to
more sensitive ranges
as
required.
It
should be possible
to
obtain
a
reading below 2.5 mV
(60
dB down).
5.4
IN
CASE OF DIFFICULTY
5.4.1
GENERAL
The overall schematic, circuit description (Section
IV),
and
troubleshooting table
(Table
5-1) can
often be used to isolate
a
problem.
Safety considerations outlined
in
Section
II
apply when
working inside
the device.
If a
problem cannot easily be
solved,
it is
best
to send the
unit to the factory using the procedure
described under paragraph
5-2.
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22
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Table of Contents
Troubleshooting
