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Maintenance
7.10
Using
an
extender
card
To
access
circuitry
on
the plug-in relay
cards
of
the
Model
707 A,
use a
Model
7070
Universal
Adapter Card.
The Model
7070 must
be configured
as
an extender card
by
placing the
configuration
jumper
in
the
EXTEND
position.
See
the
Model 7070
Instruction
Manual
for
complete
details
on
using
the card.
7.11
Cleaning
7.11.1
Backplane
Since card
rows
are extended
on
the three
analog backplanes
of
the
Model
707A
(as
explained
in
Section
3),
a contaminat-
ed backplane
will
degrade
card
isolation specifications. If
an
isolation
problem
exists,
the
backplane should be cleaned
only
after
the isolation
of each
card has
been
tested
accord-
ing
to
the
respective card manuals.
The
following procedure
is
primarily
intended
to
clean
high
impedance
PC
boards,
such
as the
Model
707A
backplane,
but
it
can be used
to clean
all
PC
boards.
To remove
the
back-
plane, refer
to
paragraph
7.5.
1.
Handle
the
board by
the
edges
only.
Do
not
touch any
board
surfaces.
When
servicing,
wear
clean,
white
cot-
ton gloves.
2.
If
making
solder
repairs
on
the
board,
use a
flux that
is
rosin
RMA
based.
Remove
the flux
from
these areas
when
the repair
is
complete.
Use
methanol and
clean
cotton
swabs
to
remove
the
flux.
Take
care not
to
spread
the
flux
to
other
areas
of
the board.
3.
Once
the flux
has
been
removed,
swab
only
the repaired
area
with
the
methanol,
then
blow-dry
the
board with
dry nitrogen
gas.
4.
After cleaning, the
board should be placed
in
a
SOT
low
humidity environment
for several hours.
7.11.2
Fan
filter
The
fan
filter,
which
is
located
on
the rear panel,
keeps
dirt
from
being
drawn
into the
instrument
by
the internal
cooling
fan.
The
filter
opening should be kept
free
of
obstructions
to
ensure proper instrument
cooling.
The
filter
should be
checked
periodically for
dirt
build-up,
and
cleaned
or replaced, as necessary.
Use
the
following
pro-
cedure
to
clean or replace
the
filter.
1
.
Disconnect
the line
cord
from
the
power
line
receptacle.
2.
Grasp
the
filter
holder,
and
pull
it
free
of
the rear panel.
3.
Remove
the
filter
element
from
the holder.
4.
Soak
the
filter
in
a
solution
of
warm
water and mild
detergent
until
clean.
Rinse thoroughly
in
clean water,
and allow
the
filter
to
dry completely before
installation.
If
a
new
filter
assembly
is
required,
one
may
be obtained
by ordering Keithley
part
number
FL-6.
NOTE
Do
not operate the
instrument with
the
fil-
ter
removed
to
avoid
dirt
build-up within
the instrument.
5.
If
necessary,
clean
the fan
guard
with
a
damp
cloth.
6.
Install
the
filter
element
in
the
holder
and
snap
the
holder
back
onto
the fan
guard.
The
two
tabs
on
the
holder should
be
oriented
at
the
right
and
left
sides.
7-16
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