Samsung RCD-750 - General Servicing Safety Checks and Precautions

1-1-6.
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Before returning an instrument to the
customer, always make a safety check of the
entire instrument, including, but not limited
to, the following items:
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
fishpapers, 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.
Be sure that there are no cabinet openings
throught 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.
Leakage Current Hot Check-With the
instrume-nt 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 App-
liances and Underwriters Laboratories (UL)
1270 (40.7). With the instrument's AC switch
first in the ON positin and then in the OFF
position, measure from a known earth
ground (metal waterpipe, 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 0.5
millamp. Reverse the instrument power cord
plug in the outlet and repeat the test.
See Figure 1.
Any measurements not within the limits
specified herein indicate a potential shock
hazard that must be ellminated before
returning the instrument to the customer.
(Reading should
not be above
0.5mA)
Device
Under Leakahe
Currant
Tester
Test all
exposed metal
surfaces
2-Wire Cord
Also test with
plug reversed
(using AC adapter
plug as required)
Earth
Ground
FIG. 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
repared and rechecked before it is returned
to the customer.
See Figure 2.