Fluke 341A - Page 34

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 343A output voltage accuracy, perform the
Model 343A
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