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AV-27920
SAFETY PRECAUTIONS
1. The design of this product contains special hardware, many
10. Isolation Check
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
manufacturer.
Replacement parts must be identical to those used in the original
circuits. Service should be performed by qualified personnel only.
(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, video/audio input and output terminals, Control knobs,
metal cabinet, screwheads, earphone jack, control shafts, etc.) to
2.
Alterations of the design or circuitry of the products should not be
be sure the product is safe to operate without danger of electrical
made.
Any
design
alterations
or
additions
will void
the
shock.
manufacturer's warranty and will further relieve the manufacturer
(1) Dielectric Strength Test
;
!
of responsibility for personal injury.or property damage resulting
The isolation between the AC primary circuit and all metal parts
i
therefrom.
exposed to the user, particularly any exposed metal part having a
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3.
Many electrical and mechanical
parts in the products have
return path to the chassis should withstand a voltage of 1100V
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special safety-related characteristics. These characteristics are
AC (r.m.s.) for a period of one second.
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often not evident from visual inspection nor can the protection
(... . Withstand a voltage of 1100V AC (r.m.s.) to an appliance
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afforded by them necessarily be obtained by using replacement
rated up to 120V, and 3000V AC (r.m.s.) to an appliance rated
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components rated for higher voltage, wattage, etc. Replacement
200V or more, for a period of one second.)
parts which
have
these
special
safety characteristics
are
This method of test requires a test equipment not generally found
i
identified
in the
parts
list of Service
manual.
Electrical
in the service trade.
components having such features are identified by shading
(2) Leakage Current Check
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on the schematics and by (A\) on the parts list in Service
Plug the AC line cord directly into the AC outlet (do not use a line
;
manual. The use of a substitute replacement which does not
isolation transformer
during this check.).
Using a "Leakage
:
have the same
safety characteristics
as the recommended
Current Tester", measure the leakage current from each exposed
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replacement part shown in the parts list of Service manual may
metal part of the cabinet, particularly any exposed metal part
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cause shock, fire, or other hazards.
having a return path to the chassis, to a known good earth ground
:
4.
Use isolation transformer when hot chassis.
(water pipe, etc.). Any leakage current must not exceed 0.5mA
(
The chassis and any sub-chassis contained in some products are
AC (r.m.s.).
i
connected
to one
side of the AC
power line. An isolation
However,
in tropical area, this must not exceed
0.2mA
AC
transformer of adequate capacity should be inserted between the
(r.m.s.).
product and the AC power supply point while performing any
@ Alternate Check Method
service on some products when the HOT chassis is exposed.
Plug the AC line cord directly into the AC outlet (do not use a line
5.
Don't short between the LIVE side ground and ISOLATED
isolation transformer during this check.). Use an AC voltmeter
(NEUTRAL)
side ground
or EARTH
side ground
when
having 1000 ohms per volt or more sensitivity in the following
repairing.
manner. Connect a 15009
10W resistor paralleled by a 0.15 4 F
Some model's power circuit: is partly different in the GND. The
AC-type capacitor between an exposed metal part and a known
difference of the GND is shown by the LIVE : (.L) side GND, the
good earth ground (water pipe, etc.). Measure the AC voltage
ISOLATED(NEUTRAL) : (+) side GND and EARTH : (@) side
across the resistor with the AC voltmeter. Move the resistor
GND.
Don't
short
between
the
LIVE
side
GND
and
connection to each exposed metal part, particularly any exposed
ISOLATED(NEUTRAL) side GND or EARTH side GND and
metal part having a return path to the chassis, and measure the
never measure with a measuring apparatus (oscilloscope etc.) the
AC voltage across the resistor. Now, reverse the plug in the AC
LIVE side GND
and ISOLATED(NEUTRAL)
side GND
or
outlet and repeat each measurement. Any voltage measured must
'EARTH side GND at the same time.
not exceed 0.75V AC (r.m.s.).
This corresponds to 0.5mA AC
If above note will not be kept, a fuse or any parts will be broken,
(r.m.s.).
:
6. if any repair has been made to the chassis, it is recommended
However, in tropical area, this must not exceed 0.3V AC (r.m.s.).
that the
B1
setting
should
be checked
or adjusted
(See
This corresponds to 0.2mA AC (r.m.s.).
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ADJUSTMENT OF B1 POWER SUPPLY).
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7. The high voltage applied to the picture tube must conform with
AC VOLTMETER
|
that specified in Service manual.
Excessive high voltage can
(HAVING 1000 2/V,
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cause
an increase in X-Ray emission, arcing and possible
OR MORE SENSITIVITY)
;
component damage, therefore operation under excessive high
GOOD
|
voltage conditions should be kept to a minimum, or should be
padi
i
prevented.
If severe
arcing occurs,
remove
the AC
power
i
immediately
and
determine
the cause
by visual
inspection
PLACE THIS PROBE
;
(incorrect installation, cracked or melted high voltage harness,
ON EACH EXPOSED
i
poor soldering, etc.). To maintain the proper minimum level of soft
15002 10W
METAL PART
X-Ray
emission,
components
in the
high voltage
circuitry
f
including the picture tube must be the exact. replacements or
41. High voltage hold down circuit check.
alternatives approved by the manufacturer of the complete
After repair of the high voltage hold down circuit, this circuit shail
8
Poe
Seek high voltage by drawing an arc. Use a high voltage
Be eee
Pe
Sen:
meter or a high voltage probe with a VTVM. Discharge the picture
pees OM
TiO Se CIOEe We Heat yates HOKIAO WN Creu:
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tube before attempting meter connection, by connecting a clip
:
lead to the ground frame and connecting the other end of the lead
This mark shows a fast
POWER CORD
through a 10k92 2W resistor to the anode button.
operating fuse, the
REPLACEMENT WARNING.
9.
When service is required, observe the original lead dress. Extra
letters indicated below
Connecting the line side of
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
manufacturers
replacement
components.
No.51370
show the rating.
power cord to" @" mark side.
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