Keithley 237

2.2
POWER
UP
PROCEDURE
2.2.1
Line
Voltage Setting
The Source Measure Unit
is
designed to operate from
105-125V
or
210-250V line
power
ranges. A special trans-
former
may
be
installed (at factory) for
90-llOV
and
195-235V ranges. The operating voltage that the instru-
ment is configured to operate
at
is indicated
on
the line
voltage slide switch located
on
the rear panel (see
Figure
2-1).
The required switch positions for the avail-
able line voltages are summarized in Table
2-l.lf
the line
voltage setting needs to
be
changed, proceed as follows:
Table
2-1. Line
Voltage
Selection
(So-60Hz)
Voltage
Selection
Line
Voltage
Switch
Position
105-125V
115V
210-250V
230V
90-llOV*
115V
195-235V*
230V
*Requires special
power
transformer, installed
at
the factory.
WARNING
Make
sure
the
Model236/237/238
is
discon-
nected from
the
power
line
and
all
other
equipment
before proceeding.
1.
Locate the line voltage switch
on
the rear panel (see
Figure 2-1). Place the blade of a screwdriver into the
slot in the switch slot
and
slide it over to the alternate
position.
2.
Install a fuse consistent
with
the operating voltage,
as described in the next paragraph.
LINE
VOLTAGE
SELECTED
[[Jill]
LINE FUSE
SLOW BLOW
0
Figure 2-1. Line Voltage Switch
and Line Fuse
+
+
SECTION2
Operation
2.2.2
Fuse
Replacement
A rear panel fuse located adjacent to the line voltage
switch (see Figure
2-1)
protects the
power
line
input
of
the Source Measure Unit.
If
the fuse needs to
be
replaced
(line voltage switch setting changed
or
suspected blown
fuse), perform the following steps:
WARNING
Make
sure
the
Source
Measure
Unit
is dis-
connected from
the
power
line
and
other
equipment
before replacing
the
fuse.
1.
With the
power
off, place the
end
of a flat-blade
screwdriver into the slot
in
the rear panel line LINE
FUSE
holder.
Push
in
gently
and
rotate the fuse car-
rier one-quarter
turn
counterclockwise. Release
pressure
on
the holder
and
its internal spring
will
push
the fuse
and
carrier
out
of
the holder.
2.
Remove the fuse
and
replace
it
with
the type recom-
mended
in
Table
2-2.
CAUTION
Do
not
use
a fuse
with
a
higher
current rating
than
specified,
or
instrument
damage
may
occur.
If
the
instrument
repeatedly
blows
fuses, locate
and
correct
the
cause
of
the
trouble before replacing
the
fuse.
See
the
service
manual
for troubleshooting informa-
tion.
Table
2-2.
Line Fuse Selection
Model
Line
Keithley
Number
Voltage
Fuse Type
Part No.
236,237
90-125V
1A,
250V,
3AG, FU-10
SloBlo
195-250V 1
/2A,
250V,
3AG,
FU-4
SloBlo
238
90-125V
1.25A,
250V,
3AG FU-28
SloBlo
195-250V 0.6A,
250V,
3AG, FU-27
Slo Blo
3.
Install
the
new
fuse
and
the fuse carrier into the
holder
by
reversing the above procedure.
2-3