ESI 250-DA - Servicing and Repair Procedures for the Impedance Bridge; Preliminary Checks Before Servicing; Systematic Checking Procedure for Troubleshooting

6
.
SERVICING
AND
REPAIR
NOTEl
Unnecessary
disassembly
of
the bridge may
cause
additional
trouble
instead
of
correcting
existing trouble.
Most
of
the
bridge
components
can
be
checked
without
removing
the
chassis
from
the
case.
If
possible,
the
instrument
should
be
returned
to
the factory
or
to
an
authorized
service
facility
if
trouble
is
suspected.
If
this is
impractical
the
following
procedure
is
recommended,
6.
1
PRELIMINARY
CHECKING
1.
Check
the
panel
controls
to
insure
that
they
are
positioned accord-
ing
to
instructions
covering
the
specific
measurement
being
per-
formed.
It
has
been
found
in many
cases that
failure to
obtain a
bridge
balance
has
been
due
to
the
wrong
position
of one
or
more of
the
panel
controls.
2.
Check
connections
between
the
bridge
binding
posts and
the
part
under
measurement.
What
appears
to
be an
intermittent
condition
inside
the
instrument
may
be
merely a
poor
outside
connection,
3.
When
capacitor
measurements
of
less
than
100
(jipf
are made,
be
sure
to
consider
zero
capacitance
of
the
bridge,
4.
If
the
bridge
cannot
be
balanced
when
measuring
capacitance,
check
the
capacitor
under
measurement
for
defects. It
may be
shorted or
open,
5.
If a
resistor
is
being
measured,
be
sure it
is not
open.
6.2
CHECKING
PROCEDURE
NOTE:
The
bridge
operator
must
acquire
a
knowledge
of
abnormal
outside
conditions
that
are
reflected in
unsatis-
factory
bridge
operation
so that
tampering
with
the
bridge
will
be
avoided.
When
it
has
been
ascertained
that
the
difficulty
is not
due to
outside
causes,
the
following
procedures
should
be
followed
in
conjunction
with
the
trouble
shooting
chart.
The
measurements
described
in 6.2
should be
made
with-
out
removing
the
bridge
chassis
from
the
case.
CAUTION:
Unqualified
personnel
must not
tamper
with
the bridge.
Unauthorized
repairs
will
invalidate
our warranty.
If
the
tests
outlined
in
the
following
paragraphs
indicate
the need
for major
repairs
,
our
Service
Department
will
be
glad
to
furnish
necessary
repair
information
as
well
as any
replacement
parts.
If
the
instru-
ment
is
more
than
one
year
old,
a
reasonable
charge
may
be
expected
for
replacement
parts
or
for
complete
reconditioning if
the
instrument
is
returned
to
the
factory.
lelsl
i
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250-DA
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