MAINTENANCE SUGGESTIONS
Your
VTVM is
capable of
continuous
daily
service requirements
over a
period
of several
yeara.
In order
for the user
to fully realize
these capabilities,
the snme
degree of care
in operation
and maintenance
should be accorded
your
instrument
that
would
be
given
any fine
piece
of
equipment.
SERVICE
WARNINGS
c
The
following
instructions
are
for
use by
qualified
personnel
only.
To
avoid clectric
shock, do not
perform
servicing
other
than
contained
in the
operating instructions
unlcss
you
are
qualified
to
do so.
a
A
shock
hazard
is
present
whcn
the case is
removed
and the unit is
operating. Line voltagc
(120
VAC)
may
be
present
on
the
input
power
cord,
on-off switch,
power
transformer, etc. any
time the
unit is connected
to ac
power.
even
if the switch
is
off.
Disconnect
the
test
leads from
external
devices and from
the mcter
before servicins.
This
B&K-PRL.CISION
Model
177VTVM
is equipped
with
aJusetl
ohms
protection
circuit.
A I
amp
pigtail
fuse
is connected
internally
between
the
comnlon
test lead
and
chassis
ground.
The
fuse
may
blow if the meteris
connected
to the 120 VAC
power
line
or
other high
AC
voltages
while
on
the ohms functions.
lf
the
ohms
protection
fuse
is open,
all
functions
of
the
vrvM
are affected
since
thc fuse
is in series
with
the common
test 1ead.
Test for
open fuse
by measuring
continuity
between
the
commr.tn
test lead
and the vrvM
chassis
using
a separate
ohm-meter.
Replace
with 1A
3AG fast
blow
on1y.
The fuse
connects
directlv
from
the
common
jack
to
the
VTVM
chassis.
Should failure
of the meter movement coil
be suspected, the continuity may be
checked
with
another
ohmmeter if
you
first connect a 10K OHM limiting resistor
in
series with the ohmmeter
test leads.
Remember:
-
NEVER
test meter coil
continuity directly with
another ohmmeter
without using a Iimiting resistance.
Do not attempt
self-repair of the meter movement. This will automaticaily void
our standard warranty on
the VTVM.
The
plastic
meter cover may through
repeated
polishing
or cleaning
accumulate
charges of static electricity. This will cause erratic
pointer
deflection whether
the
instrument is on or o{I. These static charges may
easily
be removed by
using
one
of the commercially available anti-static solutions, or a solution of any
good
liquid
dish washing detergent and
wz:ter.
Dip a clean, soft cloth in the solution and wipe
the surface of the meter cover. The
cover need not
be
removed
for
this
operation.
Faulty operation of
your
VTVM may be caused by open or shorted test leads.
Check the continuity and
resistance
periodically.
Another
frequent source of
trouble arises from
accidental
improper usage of
the
VTVM,
resulting
in failure of one or more
precision
resistors in
the
multiplier
strings.
Symptoms
of
this difficulty may be slow, upscale drifting of the
pointer,
inability to obtain
proper-
zelo adjust action, ancl of course incorrect voltage or
resistance
readings. Keep in mir-rd that
patience
and the exercise of
proper pre-
cautionary measures in
the
use of
your
instrument
are of the utmost importance
in
keeping troubles of
this
type at a minimum.
L2
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