JVC PD-Z50DX4, Service Manual

Page: 3 / 189

(No.YA229)1-3
SECTION 1
PRECAUTION
1.1 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
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
manufacturer's warranty and will further relieve the
manufacturer 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 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 features are
identified by shading on the schematics and by ( ) 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 Service manual may cause shock,
fire, or other hazards.
(4) Don't short between the LIVE side ground and
ISOLATED (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 : ( ) side
GND, the ISOLATED (NEUTRAL) : ( ) 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 the LIVE side GND and
ISOLATED (NEUTRAL) side GND or EARTH side GND at
the same time with a measuring apparatus (oscilloscope
etc.). 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 PDP POWER SUPPLY setting
should be checked or adjusted.
(6) The high voltage applied to the PDP must conform with that
specified in Service manual. Excessive high voltage can
cause an increase in 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
immediately and determine the cause by visual inspection
(incorrect installation, cracked or melted high voltage
harness, poor soldering, etc.). To maintain the proper
components in the circuitry including the PDP must be the
exact replacements or alternatives approved by the
manufacturer of the complete product.
(7) 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 through a 10k
Ω
2W
resistor to the anode button.
(8) When service is required, observe the original lead dress.
Extra 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
manufacturer's replacement 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
terminals, video/audio input and output terminals, Control
knobs, metal cabinet, screw heads, earphone jack, control
shafts, etc.) to be sure the product is safe to operate without
danger of electrical shock.
a) 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
appliance rated 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.
b) 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 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.).
However, in tropical area, this must not exceed 0.2mA 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 having 1000
Ω
per volt or more
sensitivity in the following manner. Connect a 1500
Ω
10W
resistor paralleled by a 0.15
µ
F 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, particularly 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
measurement. Any voltage measured must not exceed
0.75V AC (r.m.s.). This corresponds to 0.5mA AC (r.m.s.).
However, in tropical area, this must not exceed 0.3V AC
(r.m.s.). This corresponds to 0.2mA AC (r.m.s.).
AC VOLTMETER
(HAVING 1000 /V,
OR MORE SENSITIVITY)
PLACE THIS PROBE
ON EACH EXPOSED
METAL PART
1500 10W
0.15 F AC-TYPE
GOOD EARTH GROUND