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10.1.4
With
trims.
band:
VCA Balancing
NO
AUDIO INPUT,
balance all
six sets
of limiter
Perform the following procedure for each
limiter
a.
Check test points 301(401) to insure no gross
DC offset exists.
Less than 50 millivolts is
OK.
b.
Monitor test point 302(402).
c.
Set DRIVE full CCW.
d.
Measure the DC value on TP302(402).
e.
Set DRIVE full CWo
f.
Adjust VR301(401) to
obtain the same voltage
on TP302(402) as in step d.
g.
Quickly repeat steps
c
thru f to
obtain
minimum shift as
the DRIVE
pot is
turned
through the full sweep.
h.
Now
adjust VR302(402)
to obtain
zero volts
on TP302(402).
The setting of the DRIVE pot
should not matter.
i.
Run the DRIVE pot through a full sweep and
verify minimum shift from zero volts is
obtained.
When
all
six limiters
are shift
and offset nulled,
proceed to the next step.
10.1.5
Gain Verification
a.
Feed
the
generator into
the
LEFT
CHANNEL at
-lOdBrn,
1
KHz.
Check
that input sensitivity
is set for -10 on both channels.
b.
Set PROCESS to ON.
c.
Raise DRIVE to full
CWo
d.
Check that two to four total limiting LEDls
are on.
e.
Repeat the procedure for RIGHT channel input.
10.1.6
Limiter Test
a.
Raise the generator output to OdBm, RIGHT
channel feed only
.
b.
Observe that all the limiting LEDls are on.
c.
With
the RELEASE
TIME pot
full CW,
reduce
the
DRIVE
control
to verify
nominal
releasing of gain reduction.
d.
Measure
the output
level with
6
to 10
dB
of limiting and the OUTPUT CEILING at +6.
It
should be very
close
to OdBm.
Trim
the
output trimmer for exactly OdBm output.
e.
Repeat the procedure for a LEFT CHANNEL feed.
34
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