.
1. SAFETY PRECAUTIONS
1. The design of this product contains special hardware, many 9. Isolation Check
circuits and components especially for safety purposes. For (Safety for Electrical Shock Hazard)
continued protection, no changes should be made to the After re-assembling the product, always perform an isolation
original design unless authorized in writing by the check on the exposed metal parts of the cabinet (antenna
manufacturer. Replacement parts must be identical to those terminals, video/audio input and output terminals, Control
used in the original circuits. Service should be performed by knobs, metal cabinet, screw heads, earphone jack, control
qualified personnel only. shafts, etc.) to be sure the product is safe to operate without
danger of electrical shock.
2. Alterations of the design or circuitry of the products should 10. The surface of the TV screen is coated with a thin film which
not be made. Any design alterations or additions will void the can easily be damaged. Be very careful with it when handle
manufacturer?s warranty and will further relieve the the TV. Should the TV screen become soiled, wipe it with a
manufacturer of responsibility for personal injury or property soft dry cloth. Never rub it forcefully. Never use any cleaner
damage resulting therefrom. or detergent on it.
3. Many electrical and mechanical parts in the products have (1) Dielectric Strength Test
special safety-related characteristics. These characteristics The isolation between the AC primary circuit and all metal
are often not evident from visual inspection nor can the parts exposed to the user, particularly any exposed metal
protection afforded by them necessarily be obtained by using part having a return path to the chassis should withstand a
replacement components rated for higher voltage, wattage, voltage of 3000V AC (r.m.s.) for a period of one second.
etc. Replacement parts which have these special safety (?Withstand a voltage of 1100V AC (r.m.s.) to an appliance
characteristics are identified in the parts list of Service rated up to 120V, and 3000V AC (r.m.s.) to an appliance
manual. Electrical components having such features are rated 200V or more, for a period of one second.)
identified by shading on the schematics and by ( 9� ) on This method of test requires test equipment not generally
the parts list in Service manual. The use of a substitute found in the service trade.
replacement which does not have the same safety (2) Leakage Current Check
characteristics as the recommended replacement part Plug the AC line cord directly into the AC outlet (do not use
shown in the parts list of Service manual may cause shock, line isolation transformers during this check). Using a
fire, or other hazards ?Leakage Current Tester?, measure the leakage current from
each exposed metal part of the cabinet, particularly any
4. Don?t short between the LIVE side ground and exposed metal part having a return path to the chassis, to a
ISOLATED (NEUTRAL) side ground or EARTH side known good earth ground (water pipe, etc.). Any leakage
ground when repairing. Some model?s power circuit is current must not exceed 0.5mA AC (r.m.s.).
partly different in the GND. The difference of the GND is However, in tropical area, this must not exceed 0.2mA AC
shown by the LIVE: ( ) side GND, ISOLATED (r.m.s.).
(NEUTRAL): ( ) side GND and EARTH: ( ) side GND. ?Alternate Check Method
Don?t short between the LIVE side GND and ISOLATED Plug the AC line cord directly into the AC outlet ( do not use
(NEUTRAL) side GND or EARTH side GND and never a line isolation transformer during this check.). Use an AC
measure with a measuring apparatus (oscilloscope etc.) the voltmeter having 1000 ohms per volt or more sensitivity in
LIVE side GND and ISOLATED (NEUTRAL) side GND or the following manner. Connect a 1500
10W resistor
EARTH side GND at the same time. If above note will not be paralleled by a 0.15?F AC-type capacitor between an
kept, a fuse or any parts will be broken. exposed metal part and a known good earth ground (water
pipe, etc.). Measure the AC voltage across the resistor with
5. If any repair has been made to the chassis, it is the AC voltmeter. Move the resistor connection to each
recommended that the B1 setting should be checked or exposed metal part, particularly any exposed metal part
adjusted (See ADJUSTMENT OF B1 POWER SUPPLY). having a return path to the chassis, and measure the AC
voltage across the resistor. Now, reverse the plug in the AC
6. The high voltage applied to the picture tube must conform to outlet and repeat each measurement. Any voltage measured
that specified in Service manual. Excessive high voltage can must not exceed 0.75V AC (r.m.s.). This corresponds to
cause an increase in X-Ray emission, arcing and possible 0.5mA AC (r.m.s.).
component damage, therefore operation under excessive However, in tropical area, this must not exceed 0.3V AC
high voltage conditions should be kept to a minimum, or (r.m.s.).
should be prevented. If severe arcing occurs, remove the AC This corresponds to 0.2mA AC (r.m.s.)
power immediately and determine the cause by visual
inspection (incorrect installation, cracked or melted high
voltage harness, poor soldering, etc.). To maintain the proper
minimum level of soft X-Ray emission, components in the
high voltage circuitry including the picture tube must be the
exact replacements or alternatives approved by the
manufacturer of the complete product.
7. Do not check high voltage by drawing an arc. Use a high
voltage meter or a high voltage probe with a VTVM.
Discharge the picture tube before attempting meter
connection, by connecting a clip lead to the ground frame
and connecting the other end of the lead through a 10k
2W
resistor to the anode button.
8. When service is required, observe the original lead dress.
Extra precaution should be given to assure correct lead
dress in the high voltage circuit area. Where a short circuit
has occurred, those components that indicate evidence of
overheating should be replaced. Always use the
manufacturer?s replacement components.
3 |
ACEC
