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MAINTENANCE
Orban Model
464A
1 1
Check
overall
performance.
a)
Turn
the
L INPUT
ATTEN
and
L
OUTPUT ATTEN
controls
fully
clockwise,
turn
the
L
GATE THRESH
control
fully
counterclockwise,
and
set
the
HF
LIMIT
button
to
OPERATE.
b)
Short both
the
left
in hi
and
LEFT
in
lo
terminals
to
ground.
c)
Connect
the
audio voltmeter
to the
LEFT
OUT
HI terminal.
d) Verify
that
the residual
noise
at
the
LEFT
OUT
HI terminal
is
below
-67dBu
in
a
20-20,
000Hz
bandwidth.
e)
Remove
the
jumper(s)
between
the
LEFT
IN
HI
and
LEFT
IN
lo
terminals
and
ground.
f)
Set
the
L
LEVEL
and
L
COMPR
switches
to
OFF.
g)
Connect
the
audio
oscillator
to
the
LEFT
IN HI
terminal.
Set the
oscillator's
frequency
to
1kHz
and
its
output
level
to
-lOdBu.
h)
Adjust
the
L
INPUT
ATTEN
to
produce
a
+18.0dBu ±0.5dB
level
at
the
LEFT
out
Hi terminal.
i)
Connect
the
THD
analyzer
to the
LEFT
OUT
Hi
terminal.
j)
Verify
that
the
THD
is
below 0.06%
in
a
20-20,
000Hz
bandwidth.
k) Set the
L LEVEL
and
L
COMPR
buttons
to
on,
the
HF
umtt
button
to
operate,
and
the
L release time
control to
5.
l)
Adjust
the
L
INPUT
ATTEN
to
produce
lOdB
gain
reduction.
m)
Verify
that
THD
is
below 0.05%
in
a
20-20,000Hz bandwidth
with
the
audio
oscillator set to
35Hz, 2kHz, and 15kHz.
n)
Check
the overall
performance of
the right
channel
by
repeating the
above
for
the
right
channel.
Use
the right
channel
controls
and
terminals instead
of
the
left.
o)
Disconnect
all
test
instruments
from
the
Co-Operator.
12)
Restore
controls
and
internal
jumpers.
Return
all
controls
and jumpers
to
the positions
recorded
in step
2.
13)
Replace
the top cover.
Replace
all
six
screws
that
hold
it
in place.
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