Fluke 410B - Maintenance; Introduction; Preventive Maintenance; Troubleshooting

4-1.
INTRODUCTION
4-2.
Maintenance
of the
Model
410B DC
Power
Supply
should
consist
primarily
of
occasional
cleaning,
tube
replacement,
and
calibration.
Preventive
maintenance
is
discussed
in
paragraph 4-3.
A discussion
of trouble-
shooting
and
a
troubleshooting
chart
are
presented
in
paragraph
4-6.
Calibration
procedures
and the
equip-
ment
necessary
are
presented
in
paragraph 4-14.
WARNING
Caution
should
be
exercised
when
servicing
this
power
supply.
The
metal
shell
of
some
of the
electrolytic
capacitors
may be
as
much
as
10,
100
volts
above
chassis
ground.
Capacitors
C5
and
C219
are
high-quality,
oil-filled
units
capable
of retaining
a
charge
for
several
days.
Before
servicing
or
removing
tubes,
all
capacitors
and
plate
caps
should
be
shorted
to
the
chassis.
It is
recommended
that
the
shorting
wire
remain
connected
to
C5
and
C219
during
servicing
to
prevent
build-up
of
capacitor
voltage
due
to
dielectric
absorption.
4-3.
PREVENTIVE
MAINTENANCE
4-4.
Periodic
cleaning
of the
Model
410B
is
desirable
because
of
the
high
voltage
present.
Any
contamination
particularly
on
the
high
voltage
capacitors,
may
cause
corona
discharge,
which
will
appear
as
noise
in
the
output
voltage.
Components
may
be
cleaned
with
Freon,
or
with
a
Unt-free
rag
saturated
with
denatured
alcohol!
Ceramic
switches
may
be
cleaned
with
denatured
alcohol
or
tetrachloroethane.
After
cleaning,
the
ceramic
surface
should
be
coated
with
a
10% solution
of
Dow
Corning
silicon
fluid
(200
viscosity
grade).
Denatured
alcohol
or
tetrachloroethane
may
be
used
as a
thinner
for
the
silicon
fluid.
4-5.
Printed
circuit
boards
in the
410B are
coated
with
a
polyurethane
compound
to
prevent
moisture
ul>~
sorbtion.
If
components
are
replaced,
it
will
be
nec-
essary
to
recoat
the
circuit
board
in
the
immediate
area
of
the
part
replaced.
Aerosol
containers
of
Epocast
available
from
Furane
Plastics,
Inc.,
Los
Angeles!
California,
provide
a
convenient
way
of
recoating
the
circuit
board
area.
The
recoated
circuit
board
does
not
require
baking.
4-6.
TROUBLESHOOTING
4-7.
It
is
recommended
that
all
checks
be made
with
the
POLARITY
switch
turned
to
negative
output
polarity
and
when
possible,
the
output
voltage
set
to
500
volts!
Most
voltages
are
referred
to
the
positive
bus,
and
when
(he
output
polarity
is
negative,
the
positive
bus
is con-
nected
to
the
earth
grounded
chassis.
This
affords
some
protection
to
the
person
performing
the
tests.
4-8.
The
power
supply
should
be
allowed
to
warm-up
oefore
the
following
accuracy
checks.
Usually,
one-half
hour
of
operation
is
adequate.
Figure 4-1
is
a
list of
various
failures
and
probable
causes.
Reference
to
Figure 4-1
will
occasionally
indicate
the
cause
of
a
failure.
Components
may be
located
by
referring
to
Section
V.
A list
of
equipment
required
is
given
in
Figure 4-2.
4-9.
AUXILIARY
VOLTAGES
a.
Connect
the
881A
common
lead
to
the
410B
chassis
ground
(shell
of the
OUTPUT
connector).
b.
Set
the
POLARITY
switch
to
negative.
c.
Set
the
POWER
switch
to
ON.
d.
Set
the
OUTPUT
VOLTAGE
controls
to
zero.
e.
Set
the
HIGH
VOLTAGE
switch
to
ON.
f.
Connect
the
881
A
positive
lead
to
the
junction
of
CR206
and
CR207.
g.
The
881A should
indicate
+10
(±1)
vdc.
h.
Connect
the
88
1A positive
lead
to
the
junction
of
CR205
and
CR206.
i.
The
88
1A should
indicate
+20
(±2)
vdc.
j. Connect
the
881A
positive
lead
to
the
junction
of
CR205
and
R203.
k.
The
881A
should
indicate
+95
(±9.
5)
vdc.
l.
Connect
the
881A
positive
lead
to
the
junction
of
CR208
and
R205.
m.
The
88
1A
should
indicate
-110
(±11)
vdc.
n.
Connect
the
881A
positive
lead
to
the
positive
end
of
C211.
Also
connect
the
910A
RMS
Voltmeter
across
the
same
points
as the
881A.
o. The
88
1A
should
indicate
125
(±2.
25)
vdc.
The
910A
should
indicate
less
than
0.
005
volts
rms
ripple.
4-10.
LINE
REGULATION
AND
RIPPLE
a.
Connect
the
variable
transformer
between
the
41
0B
and
the
lino.
Sot the
transformer
to
115
volts
output.
WARNING
A
good
power
line
ground
must
be
provided
when
the
variable
transformer
is used.
b.
Connect
the
910A
and the
881A
across
the
OUTPUT
connector.
Also
connect
the
oscilloscope
across
the
OUTPUT
connector.
c.
Set the
POWER
switch
to
ON.
ci.
Set
the
HIGH
VOLTAGE
switch
to
ON.
e.
Set
the
OUTPUT
VOLTAGE
controls
to
500
volts,
and
record
the
voltage
indicated
by
the
88.1A,
1.
Increase
the
variable
transformer
output
to 127
vac,