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36
.
3.5.
CHECKING
AND
ADJUSTING
Tolerances
given
in
this
chapter apply only
in
case of
newly
adjusted instruments.
The
values
may
differ
from
those given
in
chapter
1.2.
Technical
data.
The
adjusting elements,
their
location
and
function
are
mentioned
in
chapter
3.4.
Any
adjustment, maintenance,
and
repair
of
an instrument
which
is
opened
whilst
connected
to the
mains
should be avoided
as far
as
possible and,
if
inevitable,
shall
be only
carried
out
by
skilled
personnel
familiar
with the
risk
of
shock
involved.
3.5.
1
.
General
test
3.5.
1. 1.
Power
supply
—
Check
that the current
consumption
is
<
20
mA
at
220
V
mains,
50
Hz.
—
Check
that the
filtered
voltage across capacitor
528
lies
between
+19
V
and
+22
V; and
across capacitor
531
between
—19
V
and
—22
V
(mains
voltage
220
V).
—
Check
that the
stabilized
voltage across capacitor
530
lies
between
+1 3.6
V
and +15.4
V
and
across
capacitor
533
between
—13.6
V
and —15.4
V.
—
Check
that the
filtered
voltage for
DC-operation
across
capacitor
527
is
1.4
V
±
0.2
V
(mains
voltage
220
V)
—
Depress button
R
-
Check
the
polarity
of
test
sockets
l-E
—
Depress button
C
—
Connect an
external voltage to
sockets
DC-BIAS
-
Check
the
polarity
of
test
sockets
l-E
3.5.
1.
2.
Oscillator
—
Frequency
check: button
D
not
depressed;
f
=
970 Hz
± 19
Hz
button
D
depressed;
f
=
97
Hz
± 2
Hz
—
Set range switch to position
10
nF
-
Depress button
C
—
Measure
the amplitude,
at
100 Hz and
1
kHz, between
points 7
and
11
of
push-button switch
801
A.
Right
value:
between
650
and
800
mV
rms
.
—
Set range switch to position
1
juF
-
Check
that the
amplitude,
at
1
kHz,
is
1/10
of the value
measured
with
range switch
in
position
xIO
nF
(measure
also
between
points
7
and
11)
-
Supply
a
voltage of
7
V
rms
to sockets
EXT.-AC
of the bridge
—
Check
the
amplitude between
points
801
A/7
and
801
A/1
1
at
100
Hz;
5
kHz
and
20
kHz.
Right
value:
between
600
and
750
mV
rms
3.5.
1.3.
Indication amplifier
—
Depress button
R
—
If
detuning
the bridge an oscillogram
as
shown
in
fig.
17
will
be
visible at
the +
side
of capacitor
512
f
= fnroins.
MA8825
Fig
17.
Voltage
on +
side
of
capacitor
512
—
Depress button
C
(button
D
not
depressed)
If
detuning
the
bridge,
on
the
+
side
of capacitor
512
there
must
be
a
1
kHz-sine
wave
the
tops of
which
are slightly
deformed.
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