Fluke 415B Instruction Manual 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
curren
t.
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