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Maintenance
7.3
Fuse replacement
The
line fuse,
located
on
the rear panel, protects the
power
line
input of
the instrument.
Use
the
following
procedure
to
replace
the
fuse,
if
necessary.
WARNING
Disconnect
the
instrument
from
the
power
line
and
other
equipment
before
replacing the
fuse.
1
.
With
the
power
off,
place
the
end
of a
flat-bladed
screw-
driver into the
slot
in
the rear
panel fuse
holder.
Press
in
gently
and
rotate the
fuse holder
approximately
one-
quarter
turn
counterclockwise. Release pressure
on
the
holder
and
allow
the
internal
spring
to
push
the
carrier
and
fuse out
of
the
holder.
2.
Separate
the fuse
from
the
carrier
by
carefully pulling
the
two
apart.
3.
Using
an
ohmmeter, check
the
fuse for
continuity.
A
good
fuse
will
show
low
resistance,
while a
blown
fuse
will
read high
(essentially
infinite)
resistance.
4.
If
the old fuse
is
defective, replace
it
with
the type
rec-
ommended
in
Table
7-1.
CAUTION
Do
not use
a
fuse
with a higher
rating
than
specified,
or instrument
damage
may
occur. If
the
instrument repeatedly
blows
fuses,
locate
and
correct
the cause
of
the
problem
before
resuming
opera-
tion
of the
unit.
5.
Install
the
new
fuse,
located
in
the
fuse
carrier,
by
reversing the
above
procedure.
7.4
Fixed
rack
installation
Table 7-2
lists
the
necessary
hardware
for
a
fixed
mounting
of a
Model
707A
in
a
19"
wide
rack (24
to
30"
deep).
Verify
that
all
parts
are available before
beginning
the
installation
procedure.
Table 7-2
Fixed rack
parts
Item
Description
Keithley
Part
No.
Qty-
A
Cha.ssis
Support
(left)
707-321
1
B
Chassis
Support
(right)
707-322
1
C
Nut,
#10-32
Captive
FA-
148
4
Bracket Kit
consisting
of:
BR-31
1
D
Rear Support Bracket
—
2
E
Spacer
Bar
—
2
p
Nut Bar
—
4
G
Screw,
#10-32
x
1/2"
Phil.
Binder
Hd.
—
12
Rack
preparation
1.
Select a position
in
the rack.
In
most
cases,
the
weight
of
the
Model 707
A
dictates
a
position
in
the
lower half
of
the rack.
The Model 707A
will
take
up
14"
of
vertical
space.
NOTE
The
mainframe must
be
mounted
at
a
height
that
is
an increment of
1-3/4"
from
the
top or
bottom
of
the rack.
Attempting
to
mount
the
mainframe
at
a
non-
incremental height
will
lead
to difficulties
with hole alignment.
Table
7-1
Line fuse
values
Line Voltage
Range
Fuse Rating
Keithley
Part
No.
100
to
240
VAC
5A, 250V, slow
blow,
3AG
FU-64
2.
Referring
to
Figure
7-
1,
install
two
captive nuts (item
C)
on each
front
rack
flange
at
holes 11-3/8"
and 13-1/8"
from
the
top
of
the selected space.
3.
Loosely
attach a nut bar (item
F)
to
each
rear
rack flange
with
two
binder
head screws
(item G).
See
Figure
7-2.
Mount
the
nut bars with
the outer
holes
at
the
same
level
as the
captive
nuts.
Note
that
the
hole
pattern
on
the nut
bar
is
not
symmetrical.
7-2
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