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BBE 822A - Page 8

BBE 822A
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CALIBRATION
PROCEDURE
FOR
BBE^
MODEL
822A
FOR
SERIAL
NUMBERS
EXXXXX
REVISION
L
EQUIPMENT
REQUIRED:
1)
Audio
Signal
Generator
(sine
wave)
2)
Two
digital
voltmeter
(DVM
#1
and
DVM
#2)
INITIAL
SETTINGS:
1)
DEFINITION
control
to
minimum
(completely
counter
clockwise).
2)
LO-CONTOUR
control
and
all
internal
potentiometers
to
their
middle
positions.
3)
FUNCTION
to
IN
and
POWER
to
ON.
Since
both
channels
are
identical
in
calibration
and
component
numbers
only
channel
A
will
be
outlined.
All
tests
are
done
with
a
signal
level
of
-lOdBu
(0.245Vrms)
except
for
the
CLIP
test.
The
signal
will
be
input
into
the
corresponding
channel
connector
marked
INPUT
(V
4
"
phone
jacks
unbalanced).
The
DVM
#1
will
monitor
the
output
of
the
corresponding
channel
marked
OUTPUT
(V
4
"
phone
jack
unbalanced).
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
VR4L
[VR4R]
until
DVM
reads
O.OOVdc.
POWER
SUPPLY
TEST:
1)
With
DVM
set
to
DC
volts
measure
the
positive
end
of
C29.
It
should
be
less
then
+30Vdc.
2)
With
DVM
set
to
DC
volts
measure
the
negative
end
of
C28.
It
should
be
less
then
-30Vdc.
3)
With
DVM
set
to
DC
volts
measure
pin-4
of
U11.
You
should
read
-t-15Vdc
(+/-
O.SVdc).
4)
With
DVM
set
to
DC
volts
measure
pin-11
of
U11.
You
should
read
-15Vdc
(-
1
-/-
O.SVdc).
UNITY
ADJUSTMENT
1)
Input
a
signal
of
5000Hz
(-lOdBu)
into
the
input
and
adjust
VR3L
[VR3R]
for
a
reading
of
-14.00dBu
as
read
by
DVM
#1.
2)
Input
a
signal
of
500Hz
(-lOdBu)
into
the
input
and
adjust
VR5L
[VR5R]
until
DVM
#1
reads
-II.OOdBu.
3)
Repeat
steps
1
through
2
as
some
interaction
exists
LO-CONTOUR
TEST
1)
Input
a
signal
of
50Hz
(-lOdBu)
into
the
input
and
adjust
the
LO-CONTOUR
control
to
the
middle
position
marked
"0".
DVM
#1
should
read-S.OOdBu
(0.260Vrms)(tolerance
=
-
1
-/-
I.OdBu).
2)
Turn
the
LO-CONTOUR
to
(minimum)
you
should
read
-22dBu
on
DVM
#1.(-i-
/-
I.OdBu).
3)
Turn
the
LO-CONTOUR
to
“-
1
-”
(maximum)
you
should
read
OdBu
on
DVM
#1
(+/-
I.OdBu).
DETECTOR
CHECK:
1)
Input
a
5000Hz
signal
-lO.OdBu
(0.245Vrms)
into
the
input.
2)
With
DVM
#2
(set
to
DC
volts)
measure
TP1
[TP2].
The
meter
should
read
+0.480Vdc
(+
/-
40mVdc).
3)
Input
a
500Hz
signal
-lO.OdBu
(0.245Vrms)
into
the
input.
DVM
#2
should
read
4-0.120
(-
1
-/—
4
0mVdc).
MANUAL
PROCESS
SWITCH
TEST:
1)
Switch
the
PROCESS
switch
to
MANUAL.
2)
Input
a
500Hz
signal
(-lOdBu)
into
the
input.
3)
With
the
DEFINITION
control
to
MAXIMUM
with
the
DVM
#1
measure
TP1
[TP2],
4)
The
DVM
should
read
0.400VDC
(-
1
-/-
0.030VDC).
5)
Measure
the
output
with
DVM
#2.
It
should
read
-3dBu
(-i-/-1dBu)
6)
Return
the
DEFINITION
control
to
MINIMUM
CLIP
INDICATOR
ADJUSTMENT:
1)
Input
a
500Hz
signal
into
the
input
with
an
amplitude
of
7.75Vrms.
(+20dBu)
2)
Adjust
VR6L
[VR6R]
until
the
CLIP
indicator
just
turns
on.
If
the
LED
is
already
on.
adjust
VR6L
[VR6R]
until
the
LED
goes
out
and
then
bring
it
back
up
until
it
just
turns
on.
(-i-19dBu
should
turn
it
off
{6.90Vrms})
XLR
BALANCED/UNBALANCED
TEST
1)
With
a
balanced
connection
insure
the
unit
functions
normally
as
described
above.
2)
With
an
unbalanced
connection
insure
the
unit
functions
normally
as
described
above.
BYPASS
CHECK:
1)
Switch
the
FUNCTION
switch
to
the
OUT
position.
2)
Since
the
model
822
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
0
DOVdc.
On
the
XLR
con
nectors
both
pins
2
and
3
should
be
O.OOVdc.
LED
Test:
1)
Input
a
5000Hz
signal
(@
-lOdBu)
into
the
connector
marked
CHANNEL
A
[B]
INPUT.
The
green
(-
1
-)
led
should
light.
2)
Input
a
500Hz
signal
(@
-lOdBu)
into
the
connector
marked
CHANNEL
A
[B]
INPUT.
The
red
(-)
led
should
light.
3)
Disconnect
the
signal
input
and
the
amber
(0)
led
should
light
4)
With
the
FUNCTION
switched
to
the
IN
position
the
corresponding
green
LED
should
be
lit.
5)
With
the
FUNCTION
switched
to
the
OUT
position
the
corresponding
amber
LED
should
be
lit.
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)
THIS
COMPLETES
THE
CALIBRATION
OF
THE
BBE
™
MODEL
822A

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