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INSTRUCTION
MANUAL
Digital
Multimeter
Models 172A. 173A
INITIAL
PREPARATION
2.
Line
Fuse
Requirement.
The Model
172A/l73A
uses
a single
line
fuse
to protect
the
line-operated
power
supply.
The fuse
is
a 3 AB or
3 AG, slow-blow
type.
Rep lace
with
I/4
ampere
for
II7
volts
operation
or
l/8
ampere
for
234 volrs.
IMPORTANT
A
Replace
fuse
with
correct
rating,
otherwise,
damage
to the
instrument
could
result.
3.
How to Replace
the
Line
Fuse.
The
fuse
is
installed
on the
main
circuit
board
as shown
in Figure
6-2
(Page
b-14).
The top
cover
must
be removed
to gain
access
to
the
circuit
board
as described
in Section
6.
FU-20
(1/8A)
for
234V.
Use Keithiey
FU-I7
(l/4A)
for
II7
V;
WARN I NG
t
Disconnect
the
line
cord
before
removing
the
top
cover
of
the
instrument.
'Line
voltage
is
present
at
various
points
on the
circuit
board
and represent
a SHOCK
HAZARD.
CAUT I ON
A
The fuse
installed
on the
rear
panel
of
the
Model
172A/l73A
is used
only
for
current
range
protection.
This
fuse
is
not
a line
voltage
protection
fuse.
-
b.
Battery
Power.
To operate
the
Model
172A/l73A
from
batteries,
the
Model
1723
Rechargeable
Battery
Pack must
be installed.
The /*ode1
1728 can
be either
field
or
factory-installed
(at
the
time
the
Model
172A/l73A
is
purchased).
NOTE
The Model
1728 Rechargeable
Battery
Pack can be installed
by the
user
within
me
Model
172A/l73A
at
any
time.
However,
if
the
Model
I722
Digital
Output
is
already
installed,
the
Model
1728 cannot
be used
simultaneously.
I .
How to
Install
the
Model
1728 Rechargeable
Battery
Pack.
The batteries
furnisnec
with
the
Model
1728 are
already
installed
in
the
battery
pack.
The battery
pack
in-
cludes
7 rechargeable
"C"
cells
(l.2V,
2 AMP Hr)
and
two
19.2
volt
packs
(sixteen
I.?'/-
cells
per
pack).
See Figure
2-3.
=)
Check
the
fuses
on the
Battery
Pack.
Three
fuses
are
used.
All
are
I ampere,
3AB or
3 AG, Slo-Blo
types,
Keithley
Part
Ho.
FU-IO.
b)
Check
for
proper
installation
of
batteries
in the
Battery
Pack.
If
reolace-
ment
battery
cells
are
to be insYalled,
be certain
to observe
the
proper
polarity
of
the
individual
cells
as shown
in
Figure
2-3.
C)
To install
the
Battery
Pack,
turn
the
instrument
over
so that
the
bottom
cover
faces
up.
Loosen
four
slotted
screws
on the
bottom
cover.
The screws
are
captive,
that
is
they
cannot
be removed
completely.
Turn
over
the
instrument
with
the
top
cover
facing
up,
taking
care
to hold
the
top
and bottom
covers
together.
Carefully,
remove
the
top
cover
to gain
access
to the
printed
circuit
board.
There
is
a
connection
between
the
top
cover
and the
main
circuit
board
which
must
be temporaril
removed
in order
to
free
the
top
cover.
Check
to see that
the
four
insulating
spacers
are
in position
on the
circuit
board
as shown
in
Figure
2-3.
Plug
tile
two
s-wire
connectors
(J401,
J402)
into
the
mating
receptacles
(P4Ol , ?402)
taking
care
to orient
the
connectors
as shown.
Place
the
Model
I728
in position
on tne
spacers
with
the
pack
oriented
as shown
in
Figure
2-3.
Replace
the
connector
from
the
top
cover
to
the
circuit
board.
Replace
the
top
cover.
Turn
over
t,\e
instrument
iiith
the
bottom
cover
facing
up and tighten
down
the
four
slotted-head
screws.
2-3
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