JVC AV-27BM3

SAFETY PRECAUTIONS
40.
The design of this product cenlains 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.
Alterations af the design or eitcuitry 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.
Many olectrical and mechanical parts in the products have special
salety-telated 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 vottage, wattage, etc. Replacement parts which
have th Special salety characteristics ae ides ied the paris
{ist of Service manual. Electrical components having such fea-
tures are identified by shading on the schematics and by
A\) on the parts fist in Service manual. The use of a substi-
tule replacement which does not have the same salety characteris-
tics as the recommended replacement part shown in the parts fist
of Service manual many create shock, fire, or other hazards.
Use isolation transformer when hot chassis.
The chassis and any sub-chassis contrained in some products are
connected to ono side of the AC power ling. An isolation transform-
er of adequate capacity should be inserted between the product
and the AG power supply point while perlorming any service on
sume products when the HOT chassis is axposed.
Don't short between the LIVE side ground and NEUTRAL
side grounding or EARTH side ground when repairing.
Some model's power circuit is partly different in the GND. The dil
ference of the GND is shown hy the LIVE (L) side GND, the NEU-
TRAL (fr) side GND and EARTH (@®) side GND. Don't short be-
tween the LIVE side GND and NEUTRAL side GND or EARTH side
GND and never measure with a measuring apparatus (oscilloscope
ete.) the LIVE side GND and NEUTRAL side GND or EARTH sido
GND at the same time.
If above note will not be kept, a fuse or any parts will be broken.
It any repair has been made to the chassis, it is recommended that
the By setting should be checked or adjusted (See ADJUSTMENT
OF 8) POWER SUPPLY).
The high voltage applied to the picture tube must conform with that
specitied 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, of should be prevented. If severe ar-
cing occurs, remove the AC power immedistely and determine the
cause by visual inspection (incorrect installation, crecked or melted
high voltage harness, poor soldering, etc.). To maintain the proper
minimum level of soft X-Ray emission, components if the high voll
age circuitry including the picture tube must be the exact replace-
ments or altematives approvided by the manufecturer of the com-
plete product.
Do nat 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 tead
to the ground frame and contecting the other end of the lead
through a 10k2 2W resistor to the anode button.
When service is required, observe the original fead 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,
Isolation Check
(Safety for Electrical Shock Hazard)
After te-assembling the product, always perform an isolation check
on tho exposed matal parts of the cabinet {antenna terminals, vid
ay
2)
4.
AV-27BM3
AY-27CM3
eo/audio input and output terminals, Control knobs,metal cabinet,
screwheads, earphone jack, coatral shafis, etc.) to be sure the prod-
uct is saie to operate without danger of electrical shock.
lectric Strength Test
The isolation between the AC primary circuit and ail metal parts ex-
posed 0 the user, particularly any exposed metal part having a re-
tum path to the chassis should withstand a voltage of 1100V AC
(rms) 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 (t.m.s.) to an appliance rated 200V.
of more, for @ period of one second.)
This method of test requires a test equipment not generally found
in the service Wade.
Leakage Current Check
Plug the AC fine cord directly into the AC outlet (do not use a line
isoiation transiormer during this check.) Using a "Leakage Curent
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 mnust not exceed 0,6mA AG (.m.s,).
* Alternate Check Method
Plug the AC line cord directly into the AC outlet (do not use a fine
isolation transformer during this check). Use an AG voltmeter hav.
ing 1,000 ohms per volt or more sensitivity in the following manner.
Gonnect 2 1,500 10W resistor paralleled by a 0.15pF AC-type ca-
Pacitor between an exposed metal part and a known good earth
ground (water pipe, etc.). Measure the AG 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
tum path to the chassis, and measure the AC voltage across the 1e-
sistor. Now, reverse the plug in the AC outlet and repeat each mea-
sutement, Any voltage moasured must not exceed 0.36V AG
{h.m.5.). This coresponds to 0.5mA AC (r.m.8.)
AC VOLTMETER
(HAVING 10002/V,
OR MORE SENSITIVITY)
PLACE THIS PROBE
ON EACH EXPOSED
METAL PART
15002 10W
GOOD EARTH GROUND
High voltage hoid down circuit check.
Alter repair of the high voltage hold down circuil, this circuit shail
be checked to operate conectly.
See item "How to check the high voltage hold down circuit".
i ONLY CANADA
This mark shows a fast operating fuse, the lotters indicaled
below show the rating.
(No.50718) 3