Samsung PPM42S2X/XAA, Service Manual

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1. Precautions
1-1 Safety Precautions
1. Be sure that all of the built-in protective
devices are replaced. Restore any missing
protective shields.
2. When reinstalling the chassis and its
assemblies, be sure to restore all protective
devices, including: nonmetallic control knobs
and compartment covers.
3. Make sure that there are no cabinet openings
through which people—particularly
children—might insert fingers and contact
dangerous voltages. Such openings include
the spacing between fornt cabinet and back
cabinet, excessively wide cabinet
ventilation slots, and improperly fitted back
covers.
4. Leakage Current Hot Check (Figure 1-1):
Warning: 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 Publication UL1950.5.2).
5. With the unit completely reassembled, plug
the AC line cord directly into the power
outlet. With the unit’s AC switch first in the
ON position and then OFF, measure the
current between a known earth ground (metal
water pipe, conduit, etc.) and all exposed
metal parts, including: antennas, handle
brackets, metal cabinets, screwheads and
control shafts. The current measured should
not exceed 3.5 milliamp. Reverse the power-
plug prongs in the AC outlet and repeat the
test.
Fig. 1-1 AC Leakage Test
6. Antenna Cold Check:
With the unit’s AC plug disconnected from the
AC source, connect an electrical jumper across
the two AC prongs. Connect one lead of the
ohmmeter to an AC prong. Connect the other
lead to the coaxial connector.
7. High Voltage Limits:
High voltage must be measured each time ser-
vicing is done on the B+, horizontal deflection
or high voltage circuits.
Precautions
Samsung Electronics 1-1
LEAKAGE
CURRENT
TESTER
DEVICE
UNDER
TEST
TEST ALL
EXPOSED METAL
SURFACES
2-WIRE CORD
ALSO TEST WITH
PLUG REVERSED
(USING AC ADAPTER
PLUG AS REQUIRED)
EARTH
GROUND
(READING SHOULD
NOT BE ABOVE
0.5mA)
Follow these safety, servicing and ESD precautions to prevent damage and protect against potential
hazards such as electrical shock and X-rays.