Safety Precautions - Panasonic BT-M1950Y 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 pro-
tection.no changes should be made to the original design unless
authorized in writing by the manufacturer. Replacement parts must
be identical to those used in the original circuits. Service should be
performed by qualified personnel only.
2. Alterations of the design or circuitry of the products should not be
made. Any design alterations or additions will void the manufactur-
er's warranty and will further relieve the manufacturer of responsi-
bility 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 replacement components
rated for higher voltage, wattage, etc. Replacement parts which
have these special safety characteristics are identified in the parts
list of Service manual. Electrical components having such fea-
tures are identified by shading on the schematics and by
( Lt,)
on the parts list in Service manual. The use of a substi-
tute replacement which does not have the same safety characteris-
tics as the recommended replacement part shown in the parts list
of Service manuiil may cause shock, fire, or other hazards.
4.
Use isolation transformer when hot chassis.
The chassis and any sub-chassis contrained in some products are
connected to one side of the AC power line. An isolation transform-
er 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. Don't short between the LIVE side ground and ISOLAT-
ED(NEUTRAL) side ground or EARTH side ground when re-
pairing.
Some model's power circuit is partly different in the GND. The dif-
ference of the GND is shown by the LIVE : (
.l)
side GND, the
ISOLATED(NEUTRAL) : (
'*'l
side GND and EARTH : (
@)
side
GND. Don't short between the LIVE side GND and ISOLAT-
ED(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.
6. If any repair has been made to the chassis, it is recommended that
the 8
1
setting should be checked or adjusted (See ADJUSTMENT
OF 8
1
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 dam-
age, therefore operation under excessive high voltage conditions
should be kept to a minimum, or should be prevented.
If
severe ar-
cing occurs, remove the AC power immediately and determine lhe
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 volt-
age circuitry including the picture tube must be the exact replace-
ments or alternatives approved by the manufacturer of the com-
plete product.
8. 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
9.
through a 1 Ok!'l 2W res1stor to the anode button.
When service is required, observe the original lead dress. Extra pre-
caution should be given to assure correct lead dress in the high
voltage circuit area. Where a short circuit has occurred, those com-
ponents that indicate evidence of overheating should 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 cabinet (antenna terminals, vid-
eo/audio input and output terminals, Control knobs.metal cabinet,
screwheads, earphone jack, control shafts, etc.) to be sure the prod-
uct is safe to operate without danger of electrical shock.
(1)
Dielectric Strength Test
The isolation between the AC primary circuit and all metal parts ex-
posed to the user, particularly any exposed metal part having a re-
turn path to the chassis should withstand a voltage of 11 OOV AC
(r.m.s.) for a period of one second.
( .... Withstand a voltage of 1100V AC (r.m.s.) to an appliance rat-
ed up to 120V, and 3000V AC (r.m.s.) to an appliance 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 "Leakage Current
Tester", measure the leakage curtent 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 voltmeter hav-
ing 1000 ohms per volt or more sensitivity in the following manner.
Connect a 1500!'1 1 OW resistor paralleled by a 0.15µF AC-type ca-
pacitor between an exposed metal part and a known good earth
ground (water pipe, etc.). Measure the AC voltage across the resis-
tor with the AC voltmeter. Move the resistor connection to each ex-
posed metal part. particularly any exposed metal part having a re-
turn path to the chassis, and measure the AC voltage across the re-
sistor. 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
(HAVING
1000!JN,
OR MORE SENSITIVITY)
.15µF
AC-TYPE
GOOD EARTH GROUND
11. High voltage hold down circuit check.
After repair of the high voltage hold down circuit, this circuit shall
be checked to operate correctly.
See item "How to check the high voltage hold down circuit".
(See page 32.)
• ONLY CANADA
This mark shows a fast operating fuse, the letters indicated
below show the rating.
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