JVC AV-27D203/R, Руководство по обслуживанию

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No. 51940
AV-27D303
AV-27D203
3
SAFETY PRECAUTIONS
1. The design of this product c ontains spec ial hardware, many
circuits and components s pecially for safety purposes. For
continued protection, no changes should be made to the
original des ign unless authorized in writing by the manufacturer.
Replacement parts must be identic al to thos e used in the
original circuits. Servic e should be performed by qualified
pers onnel only.
2. Alterations of the design or circuitry of the products s hould not
be made. Any design alterations or additions will void the
manufacturer's warranty and will further relieve the
manufacturer of respons ibility for pers onal injury or property
damage resulting therefrom.
3. Many electrical and mechanic al parts in the products have
special safety-related c haracteris tics. These charac teristics are
often not evident from visual inspection nor can the protection
afforded by them necess arily be obtained by using
replac ement components rated for higher voltage, wattage, etc.
Replacement parts whic h have thes e special s afety
characteristics are identified in the parts list of Service manual.
Electrical components having such features are identified
by shading on the schematics and by (
!
! !
! ) on the parts list
in Service manual. The use of a substitute replac ement which
does not have the same safety characteristics as the
recommended replac ement part shown in the parts list of
Service manual may c aus e shock, fire, or other haz ards.
4. Use isolation transformer when hot chassis.
The chassis and any sub-chassis contained in s ome products
are c onnected to one side of the AC power line. An isolation
transformer of adequate capacity should be inserted between
the product and the AC power supply point while performing
any service on some products when the HOT chassis is
exposed.
5. Do n't short between the LIVE side ground and ISOLATED
(NEUTRAL) side ground or EARTH side ground when
repairing.
Some model's power c ircuit is partly different in the GND. The
differenc e of the GND is shown by the LIVE : (
"
) s ide GND,
the ISOLATED(NEUTRAL) : ( # ) side GND and EARTH : ( $ )
side GND. Don't short between the LIVE side GND and
ISOLATED(NEUTRAL) side GND or EARTH side GND and
never measure with a meas uring apparatus (oscilloscope etc.)
the LIVE side GND and ISOLATED(NEUTRAL) side GND or
EARTH side GND at the s ame time.
If above note will not be kept, a fuse or any parts will be brok en.
6. If any repair has been made to the chassis, it is recommended
that the B1 setting should be chec ked or adjusted (See
ADJUSTMENT OF B1 POWER SUPPLY).
7. The high voltage applied to the picture tube must conform with
that specified in Service manual. Excessive high voltage can
cause an increase in X-Ray emission, arcing and possible
component damage, therefore operation under excess ive high
voltage c onditions should be kept to a minimum, or should be
prevented. If severe arc ing occurs, remove the AC power
immediately and determine the cause by visual inspection
(incorrect installation, crac ked or melted high voltage harness,
poor s oldering, etc.). T o 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.
8. Do not c hec k high voltage by drawing an arc. Us e a high
voltage meter or a high voltage probe with a VTVM. Discharge
the picture tube before attempting meter connection, by
connec ting a clip lead to the ground frame and connecting the
other end of the lead through a 10k
Ω 2W resistor to the anode
button.
9. When service is required, observe the original lead dress.
Extra precaution should be given to assure correct lead dres s
in the high voltage c ircuit area. W here a short circuit has
occurred, those c omponents that indic ate evidence of
overheating s hould be replaced. Always use the
manufacturer's replacement components.
10. Isolation Check
(Safety for Electrical Shock Hazard)
After re-assembling the product, always perform an isolation
check on the exposed metal parts of the c abinet (antenna
terminals, video/audio input and output terminals, Control
knobs, metal c abinet, screwheads, earphone jac k, c ontrol
shafts, etc.) to be sure the product is safe to operate without
danger of electrical shoc k.
(1) Dielectric Strength Test
The is olation between the AC primary circuit and all metal parts
exposed to the us er, particularly any exposed metal part having
a return path to the chassis should withstand a voltage of
1100V AC (r.m.s.) for a period of one sec ond.
(. . . . Withs tand a voltage of 1100V AC (r.m.s.) to an appliance
rated up to 120V, and 3000V AC (r.m.s.) to an applianc e rated
200V or more, for a period of one second.)
This method of test requires a test equipment not generally
found in the service trade.
(2) Leakage Current Check
Plug the AC line c ord directly into the AC outlet (do not use a
line is olation transformer during this check.). Using a "Leakage
Current Tester", measure the leakage current from each
exposed metal part of the cabinet, partic ularly any exposed
metal part having a return path to the chassis , to a known good
earth ground (water pipe, etc.). Any leakage current must not
exceed 0.5mA AC (r.m.s.).
However, in tropical area, this must not exc eed 0.2mA AC
(r.m.s.).
"
" "
" Alternate Check Method
Plug the AC line c ord directly into the AC outlet (do not use a
line isolation transformer during this check.). Use an AC
voltmeter having 1000 ohms per volt or more sensitivity in the
following manner. Connec t a 1500
Ω
10W resistor paralleled
by a 0.15
μ
F AC-type capacitor between an exposed metal
part and a known good earth ground (water pipe, etc.).
Measure the AC voltage across the resistor with the AC
voltmeter. Move the res istor connection to each exposed metal
part, particularly any exposed metal part having a return path to
the chassis , and measure the AC voltage across the resistor.
Now, revers e the plug in the AC outlet and repeat each
measurement. Any voltage measured must not exceed 0.75V
AC (r.m.s.). This corresponds to 0.5mA AC (r.m.s.).
However, in tropic al area, this must not exceed 0.3V AC
(r.m.s.). This corresponds to 0.2mA AC (r.m.s.).
0.15
μ
F AC-TYPE
1500
Ω
10W
GOOD
EARTH
GR OUND
PLACE THIS PROBE
ON EACH EXPOSED
METAL PART
AC VOLTMETER
(HAVING 1000
Ω
/V,
OR MOR E SENSITIVITY)
11. High voltage hold down circuit check.
After repair of the high voltage hold down circuit, this circuit
shall be c hec ked to operate correctly.
See item "
Ho w to check the high voltage hold down
circuit ".
A V
This mark shows a fast
operating fuse, the
letters indicated below
show the rating.