JVC AV-27920 User Manual

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 i
3. Many electrical and mechanical parts in the products have return path to the chassis should withstand a voltage of 1100V i
special safety-related characteristics. These characteristics are AC (r.m.s.) for a period of one second. I
often not evident from visual inspection nor can the protection (... . Withstand a voltage of 1100V AC (r.m.s.) to an appliance i
afforded by them necessarily be obtained by using replacement rated up to 120V, and 3000V AC (r.m.s.) to an appliance rated i
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 i
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 j
replacement part shown in the parts list of Service manual may metal part of the cabinet, particularly any exposed metal part i
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.).
i
ADJUSTMENT OF B1 POWER SUPPLY). i
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, i
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: i
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.

JVC AV-27920 Specifications

General

Brand	JVC
Model	AV-27920
Category	TV
Language	English