Advertisement
Co-Operator
MAINTENANCE
4-11
10)
Check
the output stages
and
peak output
level
meters.
a)
Turn
the
L
OUTPUT ATTEN
control
fully
clockwise,
and
set
the
L HF
LIMIT and
L
SYSTEM
buttons
to
OPERATE.
b) Verify that the
DC
offset
between
the
LEFT
OUT
HI
and
LEFT
OUT
^
terminals
is
less
than
15mV.
Verify
that
the
DC
offset
between
the
LEFT
OUT
LO
and
the
LEFT
OUT
fb
terminals
is
less
than
15mV.
There
should
be no
signal
applied
to the inputs.
c)
Verify (with the oscilloscope)
that
both
the
LEFT
OUT
HI
and
the
LEFT
OUT LO
are free
of "popcorn"
noise or
oscillation
when
observed
against
ground.
d)
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.
e)
Set
the
L LEVEL
and
L
COMPR
to
OFF,
and
the
L HF
LIMIT
button
to
DEFEAT.
f)
Load
the
LEFT
OUT
terminals
with
a
60012
resistor.
A
62Qn
'/ 2
-watt
resistor will
do.
g)
Connect
the
audio voltmeter
across the
LEFT
OUT
HI
and LEFT
out LO
terminals.
h)
Connect
the oscilloscope to the
LEFT
OUT
terminals.
i)
Advance
the
L input
atten
until slight
clipping
is
observed, then disconnect
the oscilloscope. Verify
that
the
output
level
is
at least
+19.0dBu.
j)
Turn
the
L
METER CAL
control
fully
clockwise.
k)
Rotate
the
L
output atten
control
though
its
range.
Verify
that
the
output
level varies
correspondingly,
and
that
all
segments of
the
L PEAK
output LEVEL
meter
light
when
the control
is
turned
fully
clockwise.
l)
Rotate
the
L
METER CAL
control
through
its
range.
Verify
that
the
L
PEAK
output LEVEL
meter
reading
varies
correspondingly.
m) Remove
the
600Q
resistor
from
the
LEFT
OUT
terminals.
n)
Check
the
right
channel output
stage
and
PEAK OUTPUT level
meter
by
re-
peating the
above
for the
right
channel.
Use
the
right
channel
controls, terminals,
and meter
instead
of
the
left.
o)
Disconnect
the
audio
oscillator,
audio
voltmeter,
and
oscilloscope
from
the
Co-Operator.
Advertisement
