SAMSUNG CS21A87X_BWT, CS-21A9WQ, CS15A8WT7X, CS29D8WT7X_VWT Service Manual

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 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 leakage­current tester or a metering system that
complies with American National Standards
Institute (ANIS C101.1, Leakage Current for
Appliances), 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 power­plug 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. 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
protection.

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-down”.)

Heed the high voltage limits. These include
the X–ray Protection Specifications Label, and
the Product Safety and X-ray Warning Note on
the service data schematic.

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.

1-1 Safety Precautions (Continued)

9. High voltage is maintained within specified
limits by close-tolerance, safety-related
components and adjustments. If the high
voltage exceeds the specified limits, check
each of the special components.

10. Design Alteration Warning:
Never alter or add to the mechanical or
electrical design of this unit. Example: Do not
add auxiliary audio or video connectors. Such
alterations might create a safety hazard. Also,
any design changes or additions will void the
manufacturer’s warranty.

11. Hot Chassis Warning:
Some TV receiver chassis are electrically
connected directly to one conductor of the AC
power cord. If an isolation transformer is not
used, these units may be safely serviced only
if the AC power plug is inserted so that the
chassis is connected to the ground side of the
AC source.

To confirm that the AC power plug is inserted
correctly, do the following: Using an AC
voltmeter, measure the voltage between the
chassis and a known earth ground. If the
reading is greater than 1.0V, remove the AC
power plug, reverse its polarity and reinsert.
Re-measure the voltage between the chassis
and ground.

12. Some TV chassis are designed to operate with
85 volts AC between chassis and ground,
regardless of the AC plug polarity. These units
can be safely serviced only if an isolation
transformer inserted between the receiver and
the power source.

13. Some TV chassis have a secondary ground
system in addition to the main chassis ground.
This secondary ground system is not
isolated from the AC power line. The two
ground systems are electrically separated by
insulating material that must not be defeated
or altered.

14. Components, parts and wiring that appear to
have overheated or that are otherwise
damaged should be replaced with parts that
meet the original specifications. Always
determine the cause of damage or
overheating, and correct any potential
hazards.

15. Observe the original lead dress, especially
near the following areas: Antenna wiring,
sharp edges, and especially the AC and high
voltage power supplies. Always inspect for
pinched, out-of-place, or frayed wiring. Do
not change the spacing between components
and the printed circuit board. Check the AC
power cord for damage. Make sure that leads
and components do not touch thermally hot
parts.

16. Picture Tube Implosion Warning:
The picture tube in this receiver employs
“integral implosion” protection. To ensure
continued implosion protection, make sure
that the replacement picture tube is the same
as the original.

17. Do not remove, install or handle the picture
tube without first putting on shatterproof
goggles equipped with side shields. Never
handle the picture tube by its neck. Some
“in-line” picture tubes are equipped with a
permanently attached deflection yoke; do not
try to remove such “permanently attached”
yokes from the picture tube.

18. Product Safety Notice:
Some electrical and mechanical parts have
special safety-related characteristics which
might not be obvious from visual inspection.
These safety features and the protection they
give might be lost if the replacement
component differs from the original—even if
the replacement is rated for higher voltage,
wattage, etc.

Components that are critical for safety are
indicated in the circuit diagram by shading,
( ) or ( ).
Use replacement components that have the
same ratings, especially for flame resistance
and dielectric strength specifications.
A replacement part that does not have the
same safety characteristics as the original
might create shock, fire or other hazards.

Precautions

1-2 Samsung Electronics