Fluke 415B - Page 47

415B
OUTPUT
VOLTAGE
Third dial to 20;
dials
fourth
dial to
5;
other
dials
to
zero
HIGH
VOLTAGE
STDBY/RESET
b.
Connect a
1,
000 ohm,
2 watt, resistor across
the
OUTPUT
connector.
c. Set the HIGH VOLTAGE switch to ON.
The
STDBY/
RESET lamp shall extinguish and the
HIGH
VOLT-
AGE lanp shall
illuminate.
d. Increase the output voltage in 1 volt step. The over-
load
circuit
should
operate and extinguish
the HIGH
VOLTAGE lamp within
the
range of
29
to 35 volts.
If the trip point is beyond this range, adjust as
follows:
e.
Set the HIGH
VOLTAGE switch to
STDBY/RESET.
f.
Set the
unit for maximum
current
by turning
R5
fully
counter-clockwise.
This control
is located
on
the
High
Voltage
Rectifier
P/C
board
and is ac-
cessible
through a
vent on
the left-hand
side of the
unit.
g.
Set the
OUTPUT VOLTAGE
dials to 32 volts.
NOTE!
This voltage will provide 32 milliamperes to the
1,000
ohm load resistor.
If
it is
desired that
overcurrent
trip
should occur at a lower
cur-
rent, choose
the output voltage to
provide
the
reduced current.
h.
Using an insulated screwdriver,
slowly turn R5
clockwise
until
the
overload circuit
trips and ex-
tinguishes
the HIGH VOLTAGE
lamp.
i. Set the HIGH
VOLTAGE switch to
STDBY/RESET.
Set the OUTPUT
VOLTAGE dials to
25 volts, or to
a comparable
voltage if the adjustment
was for an
overload current
less than
32 milliamperes.
j.
Repeat steps c
and d to check the
adjustment.
4-34.
Meter Calibration
a. Set the
controls of the Model 415B
as follows:
POWER
POLARITY
OUTPUT
VOLTAGE
dials
HIGH
VOLTAGE
ON
Negative
First dial to
2500;
second dial to
500;
other
dials to zero
STDBY/RESET
b.
Set the HIGH VOLTAGE
switch to
ON.
c.
Using
an insulated
screwdriver, adjust
R26 on the
Switch P/C
board
so that
the panel meter indicates
3000
volts
(±90)
volts.
NOTE!
It will be
necessary
to remove
the
cover
and
disable the
cover
interlock
to make this
adjust-
ment.
d. Set the POLARITY
switch
to Positive and check
the
+3000
volts
indication.
4-35.
TROUBLESHOOTING
4-36.
Introduction
4-37. The
information
in the
following
paragraphs
is
intended to assist
you to isolate
most common
troubles
in the
Model 41
5B
if a
systematic
approach to
trouble-
shooting is
followed. A
good
understanding of the
prin-
ciples of
operation is
necessary
to efficient trouble-
shooting,
and it
is
recommended
that you
review
Section
IH before
attempting to
troubleshoot
the instrument
in
detail.
4-38.
The
following
troubleshooting
procedure is in
such
sequence that it can be
applied to any
unit, in-
cluding
one in
which
the trouble is
totally
unknown, and
there is
doubt
whether power
can be
applied
without
causing
damage. If the unit is operable, the
Resistance
Measurement,
paragraph
4-40,
and the Standby
Power
Check,
paragraph
4-41,
may
be
omitted. The
procedure
is in
two parts:
Isolation
Checks,
paragraph 4-39,
and
Assembly
Troubleshooting, paragraph 4-45.
The Iso-
lation Checks
are
designed to localize most common
troubles as
quickly as
possible. Certain key circuit
parameters are
checked
first, which may eliminate
a
large
portion of the
circuitry
as a possible cause of
the
trouble. If
the desired
results are not achieved in the
isolation check,
reference is
given to the
appropriate
assembly
troubleshooting
procedure.
NOTE!
When
troubleshooting the unit, use negative
polarity output.
Most voltages are
referenced to
the positive bus which is
grounded when
the
output polarity is
negative.
This
provides
some
protection to the person doing troubleshooting.
4-39. isolation Checks
4-40.
RESISTANCE
MEASUREMENTS. These
checks
verify correct
resistance
between
transformer windings
and
between the
shunting
capacitors on the
high voltage
transformer.
An output
resistance
measurement reveals
a possible
short
circuit in the
output
and permits
a check
of sample
string
resistors
before the unit
is
turned
on.
a. Connect
an ohm
meter
between the
yellow lead on
the
first
OUTPUT
VOLTAGE dial
wiper
to the jade
lead on
the
transformer terminal.
The
resistance
should
increase in even
steps from
approximately
360
ohms
to 1. 1
kilo ohms as the
switch is stepped
up.
b.
Connect
the
ohmmeter across
the
front
panel
OUT-
PUT
connector. The
meter
should indicate approx-
imately
2 kilo ohms with
all
OUTPUT VOLTAGE
dials
set
to zero and
the
POLARITY
switch
set
first to
negative and then
to
positive.
As each
OUT-
PUT
VOLTAGE
dial
is
stepped
up,
the
resistance
should
increase 500 ohms
per volt
and be
approxi-
mately 1.
25 meg
ohms
with
all
dials
to
maximum.
Rev,
2
4-5