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7.3 FUSE REPLACEMENT
7.3.1 Line Fuse
A rear panel fuse protects
the power line input of the instru-
ment.
Use the following
procedure
to replace the line fuse:
WARNING
Disconnect
the instrument
from
the power
line and other
equipment
before
replacing
the fuse.
With the power
off, place
the
end of a flat-blade
screw-
driver
into the slot in the rear panel LINE FUSE holder.
Push in gently and rotate the fuse carrier one-quarter
turn
counterclockwise.
Release pressure
on the holder
and its
Internal
spring will push the fuse and carrier
out of the
holder.
Remove the fuse and replace it with the type recommended
in Table 7-2.
CAUTION
Do not
use a fuse
with
a higher
current
rating
than
specified,
or
instrument
damage
may
occur.
If the
instrument
re-
peatedly
blows
fuses,
locate
and
correct
the
Cause
of the trouble
before
replacing
the fuse.
Install the new fuse and the fuse carrier into the holder by
reversing
the above procedure.
Table 7-2. Line Fuse Selection
Line
Voltage
Fuse Type
90-125V
1/4A,
25OV. 3AG,
Slo Blo
Keithley
Part No.
FU-17
19525OV
1/8A.
25OV. 3AG,
Slo Blo
FU-20
NOTE
7.3.2 COM
Fuse
The COM fuse (F102), which
is located
internally,
protects
the instrument
from damage
in situations
where
COM is
inadvertently
connected
to earth
ground
with
input
LO
floating.
Use the following
procedure
to replace
this fuse.
WARNING
Disconnect the line cotd and all test leads and
cables from the instrument before removing the
top cover.
1. Remove
the screws that secure
the top cover to the in-
strument,
then
remove
the cover.
2. Pry the COM fuse free of its holder
using
a screwdriver.
The fuse holder
is mounted
on the inside
of the rear
panel.
3. Replace
the fuse only
with
the following
type:
l&A,
25OV, BUSS #AGC-1116, Keithley
Part No. FIJ-86-l.
CAUTION
Replace the fuse only with the recommended
type. Installing a fuse with a larger rating may
result in instrument damage.
4. Install
the top cover and
secure
it with the screws
re-
moved
earlier.
7.4 CALIBRATION
An advanced
feature of the Model 617 is its digital calibration
capabilities.
Instead
of
the
more
conventional
time-
consuming
method
of adjusting
numerous
calibration
poten-
tiometers,
the technician
need
only
apply
an appropriate
calibration
signal and digitally calibrate
the instrument,
either
from the front panel, or over the IEEE-488 bus.
Some of the calibration
procedures
will require a shielded test
fixture.
Construction
of this fixture is detailed
in Figure 7-1.
The fixture should be used wherever
a shielded
enclosure
is
called for at various
places in the procedure.
Calibration
should be performed
every 12 months,
or if the
performance
verification
procedures
in Section
5 show that
the instrument
is out of specification.
If any of the calibration
procedures
cannot
be performed
properly,
refer
to the
troubleshooting
information
in this section.
Place the V, Q GUARD
switch in the OFF posi-
tion unless otherwise
noted.
7.4.1 Recommended
Calibration
Equipment
Table
7-3 lists recommended
calibration
equipment.
Alter-
nate equipment
may be used as long as equipment
accuracy
is
at least as good as the specifications
listed in the table.
7.4.2 Environmental
Conditions
Calibration
should be performed
under laboratory
conditions
having an ambient
temperature
of 23°C kl"C
and a relative
humidity
of less than 70%
7-2
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