Advertisement
MAINTENANCE
Orban Model
464A
j)
Set
the
mode
button
to
dual.
k)
Set
the
audio
oscillator's
output
level to
-lOdBu.
l)
Adjust
the
L INPUT
ATTEN
control
until
the
second (5dB)
LED
segment
of
the
L GAIN REDUCTION
meter
just
lights.
m)
Connect
the
audio voltmeter
to
test
point
TP7, and
observe
the level
at
TP7.
n) Increase
the
audio
oscillator's
output
level to
lOdBu.
o) Verify
that
the
L GAIN REDUCTION
meter
indicates
25dB
gain
reduction,
and
that die level
at
TP7
is
no more
than l.OdB
greater
than
that
observed before
increasing the
oscillator's
output
level.
p) Set the
L
rel SHAPE
button
to
SOFT.
q)
Mute
the
oscillator,
verify
that
the
L
GAIN REDUCTION
meter
reading
decays
to
"OdB"
in
10 seconds
±2
seconds,
with
the release
slowing
as
it
nears
"OdB".
Do
not
restore the signal.
r)
Set
the
L
LEVEL
button
to
ON, and
the
L
COMPR
button
to
OFF.
s)
Restore
the
signal,
verily that the
L gain reduction
meter
indicates
22
to
25dB
gain reduction
in
2 seconds ±1
second, then
mute
the
oscillator.
t)
Set
the
L
LEVEL
button
to
OFF,
and
the
L
COMPR
button
to
ON.
u)
Restore
the
signal,
and
verify
that
the
L gain reduction
meter
indicates
15
to
22dB
gain reduction immediately.
v)
Mute
the
oscillator.
When
the gain reduction
begins
to
diminish, turn the
L
gate THRESH
control
fully
clockwise,
and
verify that the
L GAIN REDUCTION
meter
"freezes"
when
the
L
GATE THRESH
indicator
lights.
w)
Turn
the
L GATE THRESH
control
counterclockwise,
and
verify
that
the
L GAIN
reduction
meter
reading begins
to
decrease
when
the
L
GATE thresh
indicator
goes
out.
x)
Check
the
right
channel
VCA
control
circuit
and
GAIN REDUCTION
meter
by
repeating the
above
for the right channel.
Use
the
right
channel
controls, terminals,
LED,
and
meter
instead
of
the
left,
and
substitute
TP10
for
TP7.
8)
Check
high-frequency
limiters,
(part
1)
a)
Connect
the
audio
oscillator to the
LEFT
IN HI terminal,
and ground
the
LEFT
IN
LO
terminal.
Set the
oscillator's
frequency
to
1kHz
and
its
output
level to
-lOdBu.
Advertisement
