Samsung SPT4388PF, Service Manual

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1-1 Samsung Electronics
1. 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 the
picture tube and the cabinet mask,
excessively wide cabinet ventilation slots,
and improperly fitted back covers.
If the measured resistance is less than 1.0
megohm or greater than 5.2 megohms, an
abnormality exists that must be corrected
before the unit is returned to the customer.
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
A p p l i a n c e s ) , and Underwriters Laboratories
(UL Publication UL1410, 59.7).
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 0.5 milliamp. Reverse the
power-plug prongs in the AC outlet and
repeat the 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 . X-ray Limits:
The picture tube is especially designed to
prohibit X-ray emissions. To ensure
continued X-ray protection, replace the
picture tube only with one that is the same
type as the original. Carefully reinstall the
picture tube shields and mounting
hardware; these also provide X-ray
p r o t e c t i o n .
8 . High Voltage Limits:
High voltage must be measured each time
servicing is done on the B+, horizontal
deflection or high voltage circuits. Correct
operation of the X-ray protection circuits
must be reconfirmed whenever they are
serviced. (X-ray protection circuits also may
be called "horizontal disable" or "hold-
d o w n " . )
Heed the high voltage limits. These include
the X–ray Protection Specifications Label, a n d
the Product Safety and X-ray Warning Note o n
the service data schematic.
1-1 Safety Precautions
Fig. 1-1 AC Leakage Test
Follow these safety, servicing and ESD precautions to prevent damage and protect against potential
hazards such as electrical shock and X-rays.