1. Precautions
1-1 Safety Precautions
1) Before returning an instrument to the customer,Any measurements not within the limits specified
always make a safety check of the entire instrument,herein indicate a potential shock hazard that must
including, but not limited to, the following items:be eliminated before returning the instrument to
the customer.
(1) Be sure that no built-in protective devices are
defective or have been defeated during servicing.
(READING SHOULD
(1)Protective shields are provided to protect bothNOT BE ABOVE
0.5mA)
the technician and the customer. Correctly replace
LEAKAGE
DEVICECURRENT
all missing protective shields, including any
UNDERTESTER
removed for servicing convenience. TEST
(2)When reinstalling the chassis and/or other as-TEST ALL
sembly in the cabinet, be sure to put back in placeEXPOSED METER
SURFACES
all protective devices, including, but not limited to,
2-WIRE CORD
nonmetallic control knobs, insulating fish papers,
adjustment and compartment covers/shields, and
ALSO TEST WITH
EARTH
isolation resistor/capacitor networks. Do not oper-PLUG REVERSEDGROUND
(USING AC ADAPTER
ate this instrument or permit it to be operated with-PLUG AS REQUIRED)
out all protective devices correctly installed and
functioning.Fig. 1-1 AC Leakage Test
(2) Be sure that there are no cabinet openings through(4) Insulation Resistance Test Cold Check-(1) Unplug
which adults or children might be able to insertthe power supply cord and connect a jumper wire
their fingers and contact a hazardous voltage. Suchbetween the two prongs of the plug. (2) Turn on the
openings include, but are not limited to, excessive-power switch of the instrument. (3) Measure the
ly wide cabinet ventilation slots, and an improper-resistance with an ohmmeter between the
ly fitted and/or incorrectly secured cabinet backjumpered AC plug and all exposed metallic cabinet
cover.parts on the instrument, such as screwheads,
antenna, control shafts, handle brackets, etc. When
(3) Leakage Current Hot Check-With the instrumentan exposed metallic part has a return path to the
completely reassembled, plug the AC line cordchassis, the reading should be between 1 and 5.2
directly into a 120V AC outlet. (Do not use an iso-megohm. When there is no return path to the chas-
lation transformer during this test.) Use a leakagesis, the reading must be infinite. If the reading is
current tester or a metering system that compliesnot within the limits specified, there is the possibil-
with American National Standards institute (ANSI)ity of a shock hazard, and the instrument must be
C101.1 Leakage Current for Appliances andrepaired and rechecked before it is returned to the
Underwriters Laboratories (UL) 1270 (40.7). Withcustomer. See Fig. 1-2.
the instrument?s AC switch first in the ON position
and then in the OFF position, measure from a
Antenna
known earth ground (metal water pipe, conduit,
Terminal
etc.) to all exposed metal parts of the instrument
(antennas, handle brackets, metal cabinets, screw-
heads, metallic overlays, control shafts, etc.), espe-
Exposed
cially any exposed metal parts that offer an electri-
Metal Part
cal return path to the chassis.
Any current measured must not exceed 0.5mA.
Reverse the instrument power cord plug in the out-ohm
ohmmeter
let and repeat the test. See Fig. 1-1.
Fig. 1-2 Insulation Resistance Test
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