AV-20D304
SECTION 1
PRECAUTIONS
1.1 SAFETY PRECAUTIONS(10) Isolation Check
(1) The design of this product contains special hardware, many circuits(Safety for Electrical Shock Hazard)After re-assembling the
product, always perform an isolation check on the exposed metal
and components specially for safety purposes. For continued
parts of the cabinet (antenna terminals, video/audio input and output
protection, no changes should be made to the original design unless
authorized in writing by the manufacturer. Replacement parts mustterminals, Control knobs, metal cabinet, screwheads, earphone jack,
be identical to those used in the original circuits. Service should becontrol shafts, etc.) to be sure the product is safe to operate without
performed by qualified personnel only.danger of electrical shock.
(2) Alterations of the design or circuitry of the products should not bea) Dielectric Strength Test
made. Any design alterations or additions will void the manufacturer'sThe isolation between the AC primary circuit and all metal
parts exposed to the user, particularly any exposed metal part
warranty and will further relieve the manufacturer of responsibility for
personal injury or property damage resulting therefrom.having a return path to the chassis should withstand a voltage
of 1100V AC (r.m.s.) for a period of one second.
(3) Many electrical and mechanical parts in the products have special
(. . . . Withstand a voltage of 1100V AC (r.m.s.) to an appliance
safety-related characteristics. These characteristics are often not
evident from visual inspection nor can the protection afforded by themrated up to 120V, and 3000V AC (r.m.s.) to an appliance rated
necessarily be obtained by using replacement components rated for200V or more, for a period of one second.)
higher voltage, wattage, etc. Replacement parts that have theseThis method of test requires test equipment not generally
special safety characteristics are identified in the parts list of Servicefound in the service trade.
manual. Electrical components having such features areb) Leakage Current Check
Plug the AC line cord directly into the AC outlet (do not use a
identified by shading on the schematics and by ( ) on the parts
list in Service manual. The use of a substitute replacement whichline isolation transformer during this check.). Using a "Leakage
Current Tester", measure the leakage current from each
does not have the same safety characteristics as the recommended
exposed metal part of the cabinet, particularly any exposed
replacement part shown in the parts list of Service manual may cause
shock, fire, or other hazards.metal part having a return path to the chassis, to a known good
(4) Use isolation transformer when hot chassis.earth ground (water pipe, etc.). Any leakage current must not
The chassis and any sub-chassis contained in some products areexceed 0.5mA AC (r.m.s.). However, in tropical area, this must
connected to one side of the AC power line. An isolation transformernot exceed 0.2mA AC (r.m.s).
of adequate capacity should be inserted between the product and the? Alternate Check Method
Plug the AC line cord directly into the AC outlet (do not use
AC power supply point while performing any service on some
products when the HOT chassis is exposed.a line isolation transformer during this check.). Use an AC
voltmeter having 1000 ohms per volt or more sensitivity in
(5) Don't short between the LIVE side ground and ISOLATED
the following manner. Connect a 1500ohm 10W resistor
(NEUTRAL) side ground or EARTH side ground when repairing.
Some model's power circuit is partly different in the GND. Theparalleled by a 0.15?F AC-type capacitor between an
difference of the GND is shown by the LIVE : ( ) side GND, theexposed metal part and a known good earth ground (water
ISOLATED(NEUTRAL) : ( ) side GND and EARTH : ( ) side GND.pipe, etc.). Measure the AC voltage across the resistor with
Don't short between the LIVE side GND and ISOLATED(NEUTRAL)the AC voltmeter. Move the resistor connection to each
side GND or EARTH side GND and never measure with a measuringexposed metal part, particularly any exposed metal part
having a return path to the chassis, and measure the AC
apparatus (oscilloscope etc.) the LIVE side GND and
ISOLATED(NEUTRAL) side GND or EARTH side GND at the samevoltage across the resistor. Now, reverse the plug in the AC
outlet and repeat each measurement. Any voltage
time.
measured must not exceed 0.75V AC (r.m.s.). This
If above note will not be kept, a fuse or any parts will be broken.
corresponds to 0.5mA AC (r.m.s.).
(6) The high voltage applied to the picture tube must conform with that
specified in Service manual. Excessive high voltage can cause anHowever, in tropical area, this must not exceed 0.3V AC
increase in X-Ray emission, arcing and possible component damage,(r.m.s.). This corresponds to 0.2mA AC (r.m.s.).
therefore operation under excessive high voltage conditions shouldAC VOLTMETER
(HAVING 1000 /V,
be kept to a minimum, or should be prevented. If severe arcing
OR MORE SENSITIVITY)
occurs, remove the AC power immediately and determine the cause
by visual inspection (incorrect installation, cracked or melted high
voltage harness, poor soldering, etc.). To maintain the proper
0.15 F AC-TYPE
minimum level of soft X-Ray emission, components in the high
voltage circuitry including the picture tube must be the exactPLACE THIS PROBE
replacements or alternatives approved by the manufacturer of theON EACH EXPOSED1500 10W
METAL PART
complete product.GOOD EARTH GROUND
(7) If any repair has been made to the chassis, it is recommended that(11) High voltage hold down circuit check.
the B1 setting should be checked or adjusted (See ADJUSTMENTAfter repair of the high voltage hold down circuit, this circuit shall be
OF B1 POWER SUPPLY).checked to operate correctly.
(8) Do not check high voltage by drawing an arc. Use a high voltageSee item "How to check the high voltage hold down circuit".
meter or a high voltage probe with a VTVM. Discharge the picture
tube before attempting meter connection, by connecting a clip lead toThis mark shows a fast POWER CORD
REPLACEMENT WARNING.
the ground frame and connecting the other end of the lead through aoperating fuse, the
letters indicated belowConnecting the white line side of power
10k& 2W resistor to the anode button.show the rating.cord to "WHT" character side.
(9) When service is required, observe the original lead dress. ExtraPWB
precaution should be given to assure correct lead dress in the highWhite line side
voltage circuit area. Where a short circuit has occurred, those
components that indicate evidence of overheating should beA VPW
replaced. Always use the manufacturer's replacement components. WHT
(No.52103)1-3 |
ACEC
JVC
