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341
343A
4-45.
POWER-ON TEST
4-46.
This
test
determines instrument
power consump-
tion
under power-on
conditions
and
verifies
proper
opera-
tion
of
the chopper-stab
iiized
amplifier.
a.
Set
Model
341A/343A
control as follows:
FUNCTION
OFF
RANGE
10
Voltage
dials
10.00000 (Model 341 A)
10.000000 (Model 343A)
CURRENT
LIMIT
Fully
clockwise
b.
Connect
the
instrument
through
the
wattmeter
to a
115
volt
±1%,
60
Hz
source.
(3)
If
the
LIMIT
ON
lamp
does not
extinguish
in
FUNCTION
-ON
position,
check
the
high
voltage
fuse
F2, check
for
proper control
circuit
operation,
and check
controlled current
limiter
operation, paragraph
4-51.
(4)
If
the
output
voltage
is
not within
limits,
check
as
described
in
paragraph 4-34 (paragraph
4-35
for the
Mode! 343A).
4-47.
CHOPPER
AMPLIFIER
;
0)U
4-48.
This
test verifies
proper
chopper
amplifier opera-
tion
by examining
multivibrator
and chopper
amplifier
signal characteristics.
a.
Set
Model
341
A/343
A
controls
as
follows:
c.
Set
FUNCTION
switch
to'
STANDBY/RESET.
FUNCTION
ON
d.
Measure
the voltage
at
TP8
with
the
895A,
using
+
SENSE
as
common.
The
voltmeter should
indicate
between
—
1
.7
and -2.1
volts.
e.
Set
FUNCTION
switch
to
ON. The
wattmeter
should
indicate
approximately
15 watts
and
the
LIMIT
ON
lamp
should
extinguish.
f.
Repeat
step
d.
The
895A
should
indicate
between
+2.3 and +2.7
volts.
RANGE
10
Voltage
dials
10.00000 (Model 341 A)
10.000000 (Model
343A)
CURRENT
LIMIT
Fully clockwise
b.
Connect
the oscilloscope 10:1 attenuator
probe
to
test
point
TP9,
using
+
SENSE
as
common.
g.
Connect
the
895A
to the
OUTPUT
terminals.
The
895
A
should
indicate
between 9.999 and
10.001
volts dc
(9.9997
to
10.0003
volts
dc
for the
Model
343
A).
FAULT ANALYSIS
(1)
If
the
ON
lamp
does not
light in
the
FUNCTION-ON
position,
check
for possible
de-
fective
lamp
DS4
and
for
proper operation
of
the control
circuit.
(2)
If
the
TPS
voltages
are
not
within
limits,
the trouble
is
probably
in
the negative voltage
limiter.
It
may
also
be
due
to preamplifier
imbalance or
improper chopper
amplifier oper-
ation.
Check
the input voltage
to the con-
trolled
current
limiter; in
STANDBY,
it
should
be approximately
zero
volts.
Check Q35
for
balance;
with
C31
shorted, the drain voltages
of
Q35
should be equal
within
0.5
volts.
Check
the
chopper
amplifier as
described
in
paragraph
4-47.
c.
Set the oscilloscope input
to dc, vertical sensitivity to
0.2
volts
per centimeter,
and sweep speed
to
1
millisecond per centimeter.
d.
Compare
the
oscilloscope display
with
the
waveform
shown
in
Figure 4-6
for
amplitude, period,
and
symmetry.
The
observed
signal
parameters should be
equal
to
those of the given
signal
within
±10%.
1
MSEC/CM
Figure
4-6.
MULTIVIBRATOR SIGNAL
-
TP9
e.
Connect
the oscilloscope
10:1
attenuator
probe
to
TP
10,
using
+
SENSE
as
common.
4-10
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