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1. Precautions
1-1 Safety Precautions
1) Before returning an instrument to the customer,
always make a safety check of the entire
instrument, including, but not limited to, the
following items:
(1) Be sure that no built-in protective devices are
defective or have been defeated during servicing.
(1)Protective shields are provided to protect both
the technician and the customer. Correctly replace
all missing protective shields, including any
remove for servicing convenience.
(2)When reinstalling the chassis and/or other as-
sembly in the cabinet, be sure to put back in place
all protective devices, including, but not limited to,
nonmetallic control knobs, insulating fish papers,
adjustment and compartment covers/shields, and
isolation resistor/capacitor networks. Do not
operate this instrument or permit it to be operated
without all protective devices correctly installed
and functioning.
(2) Be sure that there are no cabinet openings
through which adults or children might be able to
inser t their fingers and contact a hazardous
voltage. Such openings include, but are not limited
to, excessively wide cabinet ventilation slots, and
an improperly fitted and/or incorrectly secured
cabinet back cover.
(3) Leakage Current Hot Check-With the instrument
completely reassembled, plug the AC line cord
directly into a 120V AC outlet. (Do not use a
isolation transformer during this test.) Use a
leakage current tester or a metering system that
complies with American National Standards
institute (ANSI) C101.1 Leakage Current for
Appliances and Underwriters Laboratories (UL)
1270 (40.7). With the instrument's AC switch first in
the ON position and then in the OFF position,
measure from a known earth ground (metal water
pipe, conduit, etc.) to all exposed metal parts of
the instrument (antennas, handle brackets, metal
cabinets, screwheads, metallic overlays, control
shafts, etc.), especially any exposed metal parts
that offer an electrical return path to the chassis.
Any current measured must not exceed 0.5mA.
Reverse the instrument power cord plug in the
outlet and repeat the test. See Fig. 1-1.
Any measurements not within the limits specified
herein indicate a potential shock hazard that must
be eliminated before returning the instrument to
the customer.
DEVICE
UNDER
TEST
TEST ALL
EXPOSED METER
SURFACES
2-WIRE CORD
ALSO TEST WITH
PLUG REVERSED
(USING AC ADAPTER
PLUG AS REQUIRED)
Fig. 1-1 AC Leakage Test
(4) Insulation Resistance Test Cold Check-(1) Unplug
the power supply cord and connect a jumper wire
between the two prongs of the plug. (2) Turn on the
power switch of the instrument. (3) Measure the
resistance with an ohmmeter between the
jumpered AC plug and all exposed metallic cabinet
parts on the instrument, such as screwheads,
antenna, control shafts, handle brackets, etc.
When an exposed metallic part has a return path
to the chassis, the reading should be between 1
and 5.2 megohm. When there is no return path to
the chassis, the reading must be infinite. If the
reading is not within the limits specified, there is
the possibility of a shock hazard, and the
instrument must be re-pared and rechecked before
it is returned to the customer. See Fig. 1-2.
Antenna
Terminal
Exposed
Melal Part
Fig. 1-2 Insulation Resistance Test
(READING SHOULD
NOT BE ABOVE
0.5mA)
LEAKAGE
CURRENT
TESTER
EARTH
GROUND
ohm
ohmmeter
1-1
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