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Samsung YP-T55 Service Manual: Safety Precautions

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1. Precautions
Follow these safety, servicing and ESD precautions to prevent damage and protect against potential haz-
ards such as electrical shock and X-rays.

1-1 Safety Precautions

1. Be sure that all of the built-in protective
devices are replaced.
2. When reinstalling the chassis and its
assemblies, be sure to restore all protective
devices, including 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 the
picture tube and the cabinet mask,
excessively wide cabinet ventilation slots,
and improperly fitted back covers.
4. Design Alteration Warning:
Never alter or add to the mechanical or
electrical design of the unit. Example: Do
not add auxiliary audio or video connectors.
Such alterations might create a safety haz-
ard. Also, any design changes or additions
will void the manufacturer's warranty.
5. Leakage Current Hot Check (Figure 1-1):
Warning: Do not use an isolation
transformer during this test. Use a leak-
age-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 UL1410,
With the unit completely reassembled, plug
the AC line cord directly into a 120V AC
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, etc.) and all exposed
metal parts. Examples: Handle brackets,
metal cabinets, screwheads and control
shafts. The current measured should not
exceed 0.5 milliamp. Reverse the power-
plug prongs in the AC outlet and repeat.
Test all
exposed metal
2-Wire Cord
Also test with
plug reversed
(using AC adapter
plug as required)
Fig. 1-1 AC Leakage Test
6. Insulation Resistance Cold Check:
(1) With the unit's AC plug disconnected
from the AC source, connect an electrical
jumper across the two AC prongs. (2) Set
the power switch to ON. (3) Measure the
resistance between the shorted AC plug and
any exposed metallic parts. Example:
Screwheads, antenna, control shafts or
handle brackets.
If any of the exposed metallic parts has a
return path to the chassis, the measured
resistance should be between 1 and 5.2
megohms. If there is no return path, the
measured resistance should be "infinite." If
the resistance is outside these limits, a
shock hazard might exist. See Figure 1-2
Metal Part
Fig. 1-2 Insulation Resistance Test
(Reading should
not be above
Samsung Electronics


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