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BBE 822 - Page 9

BBE 822
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Calibration
Procedure
for
the
BBE^
Model
822
Equipment
Required:
1.
Audio
Signal
Generator
(sine
wave).
2.
Two
digital
voltmeters
(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
(Va"
phone
jacks
unbalanced).
The
DVM
#1
wilt
monitor
the
output
of
the
corresponding
channel
market
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.
Unit
should
be
at
ROOM
TEMPERATURE
and
the
regulators
should
be
cool
to
touch.
Turn
unit
on.
2.
With
no
signal
present
at
the
input
(open)
measure
TP1L
[TP1R]
with
the
DVM
#2
set
to
DC
volts.
3.
Adjust
VR5L
[VRSR]
until
DVM
reads
O.OOVdc.
Power
Supply
Test:
1.
Wtih
DVM
set
to
DC
volts
measure
the
positive
end
of
C17.
It
should
be
less
then
+30Vdc.
2.
With
DVM
set
to
DC
volts
measure
the
negative
end
of
C20.
It
should
be
less
then
-30Vdc.
3.
With
DVM
set
to
DC
volts
measure
pin-4
of
U1.
You
should
read
-i-15Vdc
(
+
/-
O.SVdc).
4.
With
DVM
set
to
DC
volts
measure
pin-11
of
U1.
You
should
read
-15Vdc
(
+
/-
O.SVdc).
Output
Circuit
Adjustment:
1.
Input
a
signal
of
500Hz
(-lOdBu)
into
the
input
and
adjust
VR4
for
maximum
output
as
read
by
DVM
#1.
2.
With
DVM
#2
(set
to
AC
volts)
connected
to
TP2
adjust
VR8
until
meter
reads
0.040Vrms.
Unity
Adjustment:
1.
Inputasignalof
500Hz(-10dBu)intotheinputandadjustVR4until
DVM#1
reads
-11.0dBu(0.218Vrms
-
1
-/-
30mVrms).
2.
Inputasignal
of
5000Hz(-10dBu)intotheinputand
adjust
VR2
until
DVM
#1
reads
-11.0dBu(0.218Vrms
+/-
30mVrms).
3.
Repeat
steps
1
2
until
readings
are
correct
since
some
interaction
exists.
(INSURE
LO-CONTOUR
IS
IN
THE
MIDDLE
POSITION)
(continued
next
page)
Lo-Contour
Test:
1.
Input
a
signal
of
50Hz
(-lOdBu)
into
the
input
and
adjust
the
LO-CONTOUR
control
to
the
middle
position
marked
“O”.
DVM
#1
should
read
-IldBu
(0.218Vrms)
(tolerance
=
+/-
I.OdBu).
2.
Turn
the
LO-CONTOUR
to
(minimum)
you
should
read
-25dBu
on
DVM
#1.
(-
1
-/-
I.OdBu).
3.
Turn
the
LO-CONTOUR
to
(maximum)
you
should
read
-4.0dBu
on
DVM
#1
(
+
/-
I.OdBu).
Detector
Adjustment:
1.
Input
a
5000Hz
signal
-lO.OdBu
(0.245Vrms)
into
the
input.
2.
With
DVM
#2
(set
to
DC
volts)
measure
TP1
and
adjust
VR3
for
a
reading
of
-0.150Vdc.
3.
Input
a
500Hz
signal
-lO.OdBu
(0.245Vrms)
into
the
input.
DVM
#2
should
read
-1-0.425
(-
1
-/-
25mVdc).
Clip
Indicator
Adjustment:
1.
Input
a
500Hz
signal
into
the
input
with
an
amplitude
of
12.28Vrms.
(-K24dBu)
2.
Adjust
VR7
until
the
CLIP
indicator
just
turns
on.
If
the
LED
is
already
on
adjust
VR7
until
the
LED
goes
out
and
then
bring
it
back
up
until
it
just
turns
on.
(-K23dBu
should
turn
it
off)
XLR
Balanced
Test:
1.
With
a
balanced
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
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
TP1L
[TP1R]
with
the
DVM
set
to
DC
volts.
2.
Insure
this
voltage
is
O.OOVdc
(-
1
-/
-
25mVdc).
THIS
COMPLETES
THE
CALIBRATION
OF
THE
BBE
™
MODEL
822

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