Backplane Jumpers - Keithley 707A Instruction Manual

Maintenance
7.6
Backplane jumpers
The Model
707
A
backplane has jumpered connections
between
slots 3
and 4
for the
following general purpose
signals:
•
HI
and
LO
of analog bus #1
(e.g.,
rows
C-F
of
Model
7072).
•
HI,
LO,
and Guard of analog bus #2
(e.g.,
rows
A-H
of
Model
7071).
These jumpers
can be
removed
to selectively isolate the
sig-
nals
of
slots
1-3
from
slots
4-6.
If
all
jumpers
are
removed,
there will
be
two
3-slot general
purpose analog backplanes
in
one mainframe.
An
example system
configuration using
this
isolation
method
is
described
in
Section
3.
The
following
steps outline the
procedure
for
removing
backplane jumpers. Also
refer to
Figures 7-5 through
7-7.
WARNING
Turn
off
mainframe power and
discon-
nect the
line cord.
Ensure no
voltage
is
applied from
user
circuits,
then
remove
all
cards.
1
.
Set
the
mainframe on
a bench.
(Slightly raise the
bottom
edge
of the front panel off the bench
surface
by
placing
a
thin
book
under
the
mainframe.)
Remove
the eight
pan-head screws holding
the
handles
to
the
unit.
2.
Remove
the six flat-head screws attaching the
front
panel.
3.
Grasping
the
right
side
of
the front panel,
swing
it
to
the
left
approximately
45'
and
rest
it
on
its
edge.
CAUTION
Do
not touch the surface of the back-
plane
to
prevent
possible
contamination
from body
oil
and
dirt,
which
could
degrade
insulation resistance.
4.
The
backplane jumpers
are called out
in
Figure 7-7.
Re-
move
them by
snipping with diagonal
cutters.
If
it
is
necessary
to
clean
the
connector
side
of
the backplane
or
re-insert
backplane jumpers
(Keithley
part
number
J-15)
continue with these
steps:
5.
Remove
the
two
pan-head screws
attaching the
back-
plane support
bracket,
and
remove
the bracket.
6.
Handle
the
board by
the
edges
only.
Do
not touch
any
board
surfaces.
When
servicing,
wear
clean,
white
cot-
ton gloves.
7. 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.
8.
Once
the
flux
has been removed, swab
only
the repaired
area with methanol, and then blow-dry
the
board with
dry nitrogen
gas.
9.
After cleaning, the board should be
placed
in
a
50°C low
humidity environment
for several hours.
10.
Reassemble
the unit taking care
to align the
backplane
with
its
supports before attaching the front panel
and
handles.
7-7