Safety Precautions - Panasonic BT-M2090Y Service Manual

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SAFETY PRECAUTIONS
1. The design of this product contains special hardware, many
circuits and components specially for safety purposes.
For continued protection, no changes should be made to the
original design unless authorized in writing by the manufactur-
er. Replacement parts must be identical to those used in the
original circuits. Service should be performed by qualified per-
sonnel only.
2. Alterations of the design or circuitry of the products should not
be made. Any design alterations or additions will void the
manufacturer's warranty and will further relieve the manufac-
turer of responsibility for personal injury or property damage
resulting therefrom.
3. Many electrical and mechanical parts in the products have
special safety-related characteristics. These characteristics are
often not evident from visual inspection nor can the protection
afforded by them necessarily be obtained by using replace-
ment components rated for higher voltage, wattage, etc. Re-
placement parts which have these special safety characteris-
tics are identified in the parts list of Service manual. Electri-
cal components having such features are Identified by
shading on the schematics and by (
6
)on the parts list
in Service manual. The use of a substitute replacement
which does not have the same safety characteristics as the
recommended replacement part shown in the parts list of Ser-
vice manual may cause shock, fire, or other hazards.
4. Don't short between the LIVE side ground and ISOLAT-
ED(NEUTRAL) side ground or EARTH side ground when
repairing.
Some model's power circuit is partly different in the GND. The
difference of the GND is shown by the LIVE : (J_) side GND,
the ISOLA TED(NEUTRAL) : ( ,.Jr) 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 measuring apparatus (oscilloscope etc.)
the LIVE side GND and ISOLATED(NEUTRAL) side GND or
EARTH side GND at the same time.
If above note will not be kept, a fuse or any parts will be
broken.
5.
If
any repair has been made to the chassis, it is recommended
that the B1 setting should be checked or adjusted (See AD-
JUSTMENT OF 8
1
POWER SUPPLY).
6. 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 excessive high
voltage conditions should be kept to a minimum, or should be
prevented. If severe arcing occurs, remove the AC power im-
mediately and determine the cause by visual inspection (incor-
rect 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 in-
cluding the picture tube must be the exact replacements or al-
ternatives approved by the manufacturer of the complete prod-
uct.
7. Do not check high voltage by drawing an arc. Use a high volt-
age meter or a high voltage probe with a VTVM. Discharge
the picture tube before attempting meter connection, by con-
necting a clip lead to the ground frame and connecting the
other end of the lead through a 10kO 2W resistor to the an-
ode button.
8. When service is required, observe the original lead dress. Ex-
tra precaution should be given to assure correct lead dress in
the high voltage circuit area. Where a short circuit has oc-
curred, those components that indicate evidence of overheat-
ing should be replaced. Always use the manufacturer's re-
placement components.
9.
Isolation Check
(Safety for Electrical Shock Hazard)
After re-assembling the product, always perform an isolation
check on the exposed metal parts of the cabinet (antenna ter-
minals, video/audio input and output terminals, Control knobs,
metal cabinet, screwheads, earphone jack, control shafts, etc.)
to be sure the product is safe to operate without danger of
electrical shock.
(1) Dielectric Strength Test
The isolation between the AC primary circuit and all metal
parts exposed to the user, particularly any exposed metal part
having a return path to the chassis should withstand a voltage
of 3000V AC (r.m.s.) for a period of one second.
( .... Withstand a voltage of 1100V AC (r.m.s.) to an appli-
ance rated up
to
120V, and 3000V AC (r.m.s.) to an appli-
ance 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 cord directly into the AC outlet (do not use a
line isolation transformer during this check.). Using a "Leak-
age Current Tester", measure the leakage current from each
exposed metal part of the cabinet, particularly 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.).
• Alternate Check Method
Plug the AC line cord directly into the AC outlet (do not use a
line isolation transformer during this check.). Use an AC volt-
meter having 1 000 ohms per volt or more sensitivity in the fol-
lowing manner. Connect a 15000 1 OW resistor paralleled by
a 0.15µF 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 resistor connection to each exposed metal part, par-
ticularly any exposed metal part having a return path to the
chassis, and measure the AC voltage across the resistor.
Now, reverse the plug in the AC outlet and repeat each mea-
surement. Any voltage measured must not exceed 0.35V AC
(r.m.s.). This corresponds to 0.5mA AC (r.m.s.).
~
AC VOLTMETER
\,,,J--./
(HAVING 1000ON,
OR MORE SENSITIVITY)
.15µF AC-TYPE
GOOD EARTH GROUND
Fig.A
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