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BBE 862 - Page 14

BBE 862
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CALIBRATION
PROCEDURE
FOR
THE
BBE
862
NOTE:
THIS
UNIT
WAS
CALIBRATED
AT
THE
FACTORY.
THIS
IS
FOR
QUALIFIED
SERVICE
PERSONNEL
ONLY.
EQUIPMENT
REQUIRED:
1)
Audio
Signal
Generator
(sine
wave)
FOR
SERIAL
NUMBERS
RXXXXX
2)
T
wo
digital
voltmeter
(DVM
#1
and
DVM
#2)
REVISION
A.1
AUGUST
25,
1992
INITIAL
SETTINGS:
1)
BBE
PROCESS
control
(VR4,
VR8)
to
minimum
(completely
counter
clockwise).
2)
LO
CONTOUR
control
and
all
internal
potentiometers
(VR1
VR2,
VR3,
VR5,
VR6,
VR7)
to
their
middle
positions.
3)
FUNCTION
to
IN
and
POWER
to
ON.
Since
both
channels
are
identical
in
calibration,
only
channel
A
will
be
outlined.
Channel
B
will
be
in
brackets
[
].
All
tests
are
done
with
a
signal
level
of
OdBu
(0.775Vrms)
except
where
noted.
The
signal
will
be
input
into
the
corresponding
channel
connector
marked
INPUT
(1/4"
phone
jacks
balanced).
The
DVM
#1
will
monitor
the
output
of
the
corresponding
channel
marked
OUTPUT
(1/4"
phone
jack
balanced).
The
DVM
#2
will
be
used
to
measure
various
test
points
in
the
test
procedure,
(relative
to
ground)
PROCEDURE:
OFFSET
ADJUSTMENT:
1)
With
no
signal
present
at
the
input
(open)
measure
TP1
[TP2]
with
the
DVM
#2
set
to
DC
volts.
2)
Adjust
VR1
[VR5]
until
DVM
reads
O.OOVdc.
POWER
SUPPLY
TEST:
1
)
With
DVM
set
to
DC
volts
measure
the
positive
end
of
C81
.
It
should
be
less
then
+30Vdc.
2)
With
DVM
set
to
DC
volts
measure
the
negative
end
of
C82.
It
should
be
less
then
-30Vdc.
3)
With
DVM
set
to
DC
volts
measure
pin
8
of
U11.
You
should
read
+15Vdc
(+/-
O.SVdc).
4)
With
DVM
set
to
DC
volts
measure
pin
4
of
U11.
You
should
read
-15Vdc
(+/-
O.SVdc).
UNITY
ADJUSTMENT:
1)
Input
a
signal
of
5000Hz
(OdBu)
into
the
input
and
adjust
VR2
[VR6]
for
a
reading
of
-O.SOOdBu
as
read
by
DVM
#1.
2)
Input
a
signal
of
500Hz
(OdBu).
Confirm
that
the
DVM
#1
reads
-O.SOOdBu
(+/-0.S00
dBu).
LO-CONTOUR
TEST:
1)
Input
a
signal
of
50Hz
(OdBu)
into
the
input
and
adjust
the
LO-CONTOUR
control
to
the
middle
position.
DVM
#1
should
read
+1.00dBu
(+/-
I.OdBu).
2)
Turn
the
LO-CONTOUR
to
minimum.
You
should
read
-13.5dBu
on
DVM
#1.(+/-
I.OdBu).
3)
Turn
the
LO-CONTOUR
to
maximum.
You
should
read
-t-OdBu
on
DVM
#1
(+/-
I.OdBu).
DETECTOR
CHECK:
1)
Input
a
5000Hz
signal
O.OdBu
(0.775Vrms)
into
the
input.
2)
With
DVM
#2
(set
to
DC
volts)
measure
TP1
[TP2].
The
meter
should
read
-1.800VDC
(+/-
SOmVdc).
3)
Input
a
500Hz
signal
O.OdBu
(0.775Vrms)
into
the
input.
DVM
#2
should
read
-1.800VDC
(+/-
SOmVdc).
LED
TEST:
1)
Input
a
5000Hz
signal
@
-20dBu
(77.5mVrms)
into
the
connector
marked
CHANNEL
A
[B]
INPUT.
The
"YELLOW,"
-20
LED
should
light.
2)
Change
the
input
signal
to
-lOdBu
(245mVrms.)
The
"YELLOW,"
-10
LED
should
light.
3)
Change
the
input
signal
to
OdBu
(775mVrms.)
The
"GREEN,"
0
LED
should
light.
4)
Change
the
input
signal
to
-rlOdBu
(2.250Vrms.)
The
"GREEN,"
-flO
LED
should
light
5)
With
the
FUNCTION
switched
to
the
IN
position
the
corresponding
"GREEN"
LED
should
light.
6)
With
the
FUNCTION
switched
to
the
OUT
position
the
corresponding
"YELLOW"
LED
should
light.
CILIP
INDICATOR
TEST:
1)
Input
a
500Hz
signal
with
an
amplitude
of
+20dBu
(7.750Vrms)
into
the
connector
marked
INPUT
CHANNEL
A
[B].
Insure
the
corresponding
CLIP
LED
is
fully
lit
for
each
channel.
2)
Change
the
input
signal
level
to
-t-ISdBu
(6.904Vrms.)
The
CLIP
LED
should
not
be
lit
for
either
channel.
XLR
BALANCED/UNBALANCED
TEST:
1
)
Measure
pins
#2
and
#3.
They
should
measure
-6dBu
(-f/-!).
2)
Confirm
the
unit
functions
normally
as
described
above.
3)
Ground
pin
#3
of
the
XLR.
Insure
the
unit
functions
normally
as
described
above.
BYPASS
CHECK:
1)
Switch
the
FUNCTION
switch
to
the
OUT
position.
2)
Since
the
model
862
has
“hard
wire"
bypass
whatever
is
present
at
the
input
of
the
device
should
be
present
at
the
output
when
in
bypass
mode.
Verify
that
this
is
so.
DC
VOLTAGE
AT
OUTPUT
TEST:
1
)
Measure
the
output
jacks
to
ground
with
the
DVM
set
to
DC
volts.
The
voltage
must
be
O.OOVdc.
On
the
XLR
connectors
both
pins
2
and
3
should
be
O.OOVdc.
OFFSET
DRIFT
TEST:
1)
With
no
signal
present
at
the
input
(open)
measure
TP1
[TP2]
with
the
DVM
set
to
DC
volts.
2)
Insure
this
voltage
is
O.OOVdc
(+
1
-
0.25mVdc)
END
TEST
12

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