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PRECAUTIONS
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 removed for servicing convenience.
(2)When reinstalling the chassis and/or other assembly 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 insert 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 an 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.
Any measurements not within the limits specified herein indicate
a potential shock hazard that must be eliminated before returning
the instrument to the customer.
(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 repared
and rechecked before it is returned to the customer. See Fig. 2.
(READING SHOULD
NOT BE ABOVE
0.5mA)
LEAKAGE
CURRENT
TESTER
EARTH
GROUND
EXPOSED METER
SURFACES
ALSO TEST WITH
PLUG REVERSED
(USING AC ADAPTER
PLUG AS REQUIRED)
2-WIRE CORD
Fig. 1 AC Leakage Test
Fig. 2 Insulation Resistance Test
2) Read and comply with all caution and safety related notes on or
inside the cabinet, or on the chassis.
3) Design Alteration Warning-Do not alter or add to the mechanical
or electrical design of this instrument. Design alterations and
additions, including but not limited to, circuit modifications and
the addition of items such as auxiliary audio output connections,
might alter the safety characteristics of this instrument and create
a hazard to the user. Any design alterations or additions will
make you, the servicer, responsible for personal injury or
property damage resulting therefrom.
4) Observe original lead dress. Take extra care to assure correct
lead dress in the following areas:
(1) near sharp edges, (2) near thermally hot parts (be sure that
leads and components do not touch thermally hot parts), (3) the
AC supply, (4) high voltage, and (5) antenna wiring. Always
inspect in all areas for pinched, out-of-place, or frayed wiring,
Do not change spacing between a component and the printed-
circuit board. Check the AC power cord for damage.
5) Components, parts, and/or wiring that appear to have overheated
or that are otherwise damaged should be replaced with
components, parts and/or wiring that meet original
specifications.
Additionally, determine the cause of overheating and/or damage
and, if necessary, take corrective action to remove any potential
safety hazard.
Antenna
Terminal
Exposed
Metal Part
ohm
ohmmeter
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