Important Safeguards And Precautions - Sharp LC-15AV1U Service Manual

IMPORTANT SAFEGUARDS AND PRECAUTIONS

Prior to shipment from the factory, our products are strictly inspected for recognized product safety and electrical
codes of the countries in which they are to be sold. However, in order to maintain such compliance, it is equally
important to implement the following precautions when a set is being serviced.
Safety Precautions for TV Circuit
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:
a. Be sure that no built-in protective devices are
defective and have been defeated during servicing.
(1) Protective shields are provided on this chassis 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 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. Servicers who defeat safety features
or fail to perform safety checks may be liable for
any resulting damage.
b. Be sure that there are no cabinet openings through
which an adult or child might be able to insert their
fingers and contact a hazardous voltage. Such
openings include, but are not limited to, (1) spacing
between the picture tube and the cabinet mask,
(2) excessively wide cabinet ventilation slots, and
(3) an improperly fitted and/or incorrectly secured
cabinet back cover.
c. Antenna Cold Check - With the instrument AC plug
removed from any AC source, connect an electrical
jumper across the two AC plug prongs. Place the
instrument AC switch in the on position. Connect
one lead of an ohmmeter to the AC plug prongs tied
together and touch the other ohmmeter lead in turn
to each tuner antenna input exposed terminal screw
and, if applicable, to the coaxial connector. If the
measured resistance is less than 1.0 megohm or
greater than 5.2 megohm, an abnormality exists that
must be corrected before the instrument is returned
to the customer. Repeat this test with the instrument
AC switch in the off position.
d. 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) 1410, (50.7). With
the instrument 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 cabinet, screw heads, 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
milli-ampere. Reverse the instrument power cord
plug in the outlet and repeat the test.
READING SHOULD
NOT BE ABOVE 0.5 mA
DEVICE
BEING
TESTED
ALSO TEST WITH
PLUG REVERSED
USING AC
ADAPTER PLUG
AS REQUIRED
ANY MEASUREMENTS NOT WITHIN THE LIMITS
SPECIFIED HEREIN INDICATE A POTENTIAL
SHOCK HAZARD THAT MUST BE ELIMINATED
BEFORE RETURNING THE INSTRUMENT TO THE
CUSTOMER OR BEFORE CONNECTING THE
ANTENNA OR ACCESSORIES.
e. X-Radiation and High Voltage Limits - Because
the picture tube is the primary potential source of X-
radiation in solid-state TV receivers, it is specially
constructed to prohibit X-radiation emissions. For
continued X-radiation protection, the replacement
picture tube must be the same type as the original.
Also, because the picture tube shields and mounting
hardware perform an X-radiation protection function,
they must be correctly in place. High voltage must be
measured each time servicing is performed that
involves B+, horizontal deflection or high voltage.
Correct operation of the X-radiation protection circuits
also must be reconfirmed each time they are serviced.
(X-radiation protection circuits also may be called
"horizontal disable" or "hold down.") Read and apply
the high voltage limits and, if the chassis is so
equipped, the X-radiation protection circuit
2-1
LEAKAGE
CURRENT
TESTER
+
TEST ALL EXPOSED
METAL SURFACES
EARTH
GROUND
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LCVISP