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d.
Remove
the
93 IB from
the
output
of
the preampli-
fier
and
connect
the oscilloscope
in
its
place.
e.
Repeat
step
c.
The
p-p
ripple
should
not.
exceed
the
values
shown.
FAULT
ANALYSIS
If
ripple
is
excessive,
check
for
ground
loops
in
equipment
connections
and
check
for
proper
operation
of
the
preamplifier
and chopper
amplifier,
paragraphs 4-45
and
4-47.
4-32.
OUTPUT VOLTAGE ACCURACY
4-33,
If
the instrument has
successfully
passed
the
line,
load,
and
ripple
tests,
it
can be
assumed
to
be
operating
correctly.
The
output
voltage
accuracy
test
compares
the instrument output
voltage
to
the
accuracy
specifica-
tions given
in
Section
I.
4-3
4.
Model
341
A
Output
Voltage
Test.
a.
Connect
the
895A
to the
Model
341
A OUTPUT
terminals,
with
the negative
OUTPUT
terminal con-
nected
to chassis
ground.
4-36.
TROUBLESHOOTING
4-37.
In the
following checks, paragraphs
4-39 through
4-59, the
performance
of
the
major
functional
circuitry
is
examined by
an appropriate
test.
These
tests
together
with
specific
troubleshooting, information
are
intended
to aid
in
locating
instrument
malfunctions.
The
tests
begin
with
power-off
resistance
checks, proceed
to
standby
and power-
on
checks,
and conclude
with
specific
functional
circuit
checks.
The
tests
should be performed
in
the order given,
unless the general trouble location
is
suspected beforehand.
4-38.
When
measuring
voltages
on
the
circuit
boards,
it
is
recommended
that
the
major
portion
of
the voltage
probe be
wrapped
with
insulating tape.
This
will
reduce
the
possibility
of
damaging
a transistor
due
to
an
accidental
short
circuit.
For
component
locations, refer to
the
illus-
trated parts
breakdown
in
Section
V.
WARNING!
Voltages hazardous
to
life
will
be
present.
Use
extreme
caution.
When
troubleshooting,
it
is
recommended
that the
+
OUTPUT
terminal
be
jumpered
to the
chassis
ground
terminal
to
reduce
shock
hazard.
b.
Set the
Model
341
A
controls as
shown
in
Figure 4-11.
The
output
voltages
should
be
as
indicated
in
column
2.
FAULT
ANALYSIS
If
output
voltages
are
incorrect,
check
the
+15
volt reference
adjustment, paragraph 4-64;
the zero
output
adjustments,
paragraph 4-65;
the range adjustments, paragraph
4-67
;
and
the
beta
string,
paragraph
4-57.
4-39.
TEST POINT RESISTANCE
CHECK
4-40.
This
test
consists
of
a resistance
check of
all
power
supply outputs within the instrument.
a.
Set
Model
341A/343A
controls
as
follows:
FUNCTION
OFF
RANGE
10
Voltage
Dials
10.00000 (Model 341
A)
10.000000 (Model
343A)
4-35.
Model 343A Output
Voltage
Test.
To
check
the
Model 343
A
output
voltage
accuracy,
perform
the
Model 343
A
calibration verification
procedure, paragraph
4-84,
steps
a
through
h.
The
output
voltages
should be
as
indicated
in
Figure 4-17,
column
2.
—
FAULT
ANALYSIS
~j
If
output
voltages are incorrect,
check
the
+15
volt
reference adjustment,
paragraph 4-73;
the
zero
output
adjustments, paragraphs
4-74
and
4-79; the range adjustments, paragraph 4-82;
and
the beta
string,
paragraph
4-57.
CURRENT
LIMIT
Fully clockwise
b.
Connect
853A
common
to
+
SENSE.
Measure
the
resistance
between
the
following points
and
the
+
SENSE
terminal. Resistance
should be
as
indicated.
TEST POINT
APPROXIMATE
RESISTANCE
IN
OHMS
TP2
2500
TPS
3700
TPS
>!
00k
TP6
340
TP7
>100k
-
SENSE
58
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