ALI M5677, Service Manual

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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
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 opening 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
and 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.
AC Leakage Test
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 wore
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.
Insulation Resistance Test
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