Important Safety Notice; Service Information - Zenith D52WLCD Series Service Manual

PRODUCT SAFETY SERVICING GUIDELINES FOR AUDIO-VIDEO PRODUCTS

IMPORTANT SAFETY NOTICE

This manual was prepared for use only by properly trained audio-
video service technicians.
When servicing this product, under no circumstances should the orig-
inal design be modified or altered without permission from Zenith
Electronics Corporation. All components should be replaced only with
types identical to those in the original circuit and their physical loca-
tion, wiring and lead dress must conform to original layout upon com-
pletion of repairs.
Special components are also used to prevent shock and fire hazard.
These components are indicated by the letter "x" included in their
component designators and are required to maintain safe perfor-
mance. No deviations are allowed without prior approval by Zenith
Electronics Corporation.
Circuit diagrams may occasionally differ from the actual circuit used.
This way, implementation of the latest safety and performance
improvement changes into the set is not delayed until the new service
literature is printed.
CAUTION:
Do not attempt to modify this product in any way.
Never perform customized installations without manu-
facturer's approval. Unauthorized modifications will not
only void the warranty, but may lead to property dam-
age or user injury.
Service work should be performed only after you are
thoroughly familiar with these safety checks and servic-
ing guidelines.
GRAPHIC SYMBOLS
The exclamation point within an equilateral triangle is
intended to alert the service personnel to important
safety information in the service literature.
The lightning flash with arrowhead symbol within an
equilateral triangle is intended to alert the service per-
sonnel to the presence of noninsulated "dangerous
voltage" that may be of sufficient magnitude to consti-
tute a risk of electric shock.
The pictorial representation of a fuse and its rating with-
in an equilateral triangle is intended to convey to the
service personnel the following fuse replacement cau-
tion notice:
CAUTION: FOR CONTINUED PROTECTION AGAINST
RISK OF FIRE, REPLACE ALL FUSES WITH THE
A V
SAME TYPE AND RATING AS MARKED NEAR EACH
FUSE.

SERVICE INFORMATION

While servicing, use an isolation transformer for protection from AC
line shock.
After the original service problem has been corrected, make a check
of the following:
FIRE AND SHOCK HAZARD
1. Be sure that all components are positioned to avoid a possibility of
adjacent component shorts. This is especially important on items
transported to and from the repair shop.
2. Verify that all protective devices such as insulators, barriers, cov-
ers, shields, strain reliefs, power supply cords, and other hardware
have been reinstalled per the original design. Be sure that the safe-
ty purpose of the polarized line plug has not been defeated.
3. Soldering must be inspected to discover possible cold solder joints,
solder splashes, or sharp solder points. Be certain to remove all
loose foreign particles.
4. Check for physical evidence of damage or deterioration to parts and
components, for frayed leads or damaged insulation (including the
AC cord), and replace if necessary.
5. No lead or component should touch a high current device or a resis-
tor rated at 1 watt or more. Lead tension around protruding metal
surfaces must be avoided.
6. After reassembly of the set, always perform an AC leakage test on all
exposed metallic parts of the cabinet (the channel selector knobs,
antenna terminals, handle and screws) to be sure that set is safe to
operate without danger of electrical shock. DO NOT USE A LINE ISO-
LATION TRANSFORMER DURING THIS TEST. Use an AC voltmeter
having 5000 ohms per volt or more sensitivity in the following manner:
Connect a 1500 ohm, 10 watt resistor, paralleled by a .15 mfd 150V AC
type capacitor between a known good earth ground water pipe, con-
duit, etc.) and the exposed metallic parts, one at a time.
Measure the AC voltage across the combination of 1500 ohm resistor
and .15 mfd capacitor. Reverse the AC plug by using a non-polarized
adaptor and repeat AC voltage measurements for each exposed metal-
lic part. Voltage measured must not exceed 0.75 volts RMS. This cor-
responds to 0.5 milliamp AC. Any value exceeding this limit constitutes
a potential shock hazard and must be corrected immediately.
TIPS ON PROPER INSTALLATION
1. Never install any receiver in a closed-in recess, cubbyhole, or
closely fitting shelf space over, or close to, a heat duct, or in the
path of heated air flow.
2. Avoid conditions of high humidity such as: outdoor patio installa-
tions where dew is a factor, near steam radiators where steam leak-
age is a factor, etc.
3. Avoid placement where draperies may obstruct venting. The cus-
tomer should also avoid the use of decorative scarves or other cov-
erings that might obstruct ventilation.
4. Wall- and shelf-mounted installations using a commercial mounting
kit must follow the factory-approved mounting instructions. A prod-
uct mounted to a shelf or platform must retain its original feet (or the
equivalent thickness in spacers) to provide adequate air flow across
the bottom. Bolts or screws used for fasteners must not touch any
parts or wiring. Perform leakage tests on customized installations.
5. Caution customers against mounting a product on a sloping shelf or
in a tilted position, unless the receiver is properly secured.
6. A product on a roll-about cart should be stable in its mounting to the cart.
Caution the customer on the hazards of trying to roll a cart with
small casters across thresholds or deep pile carpets.
7. Caution customers against using a cart or stand that has not been
listed by Underwriters Laboratories, Inc. for use with its specific
model of television receiver or generically approved for use with
TVs of the same or larger screen size.
8. Caution customers against using extension cords. Explain that a
forest of extensions, sprouting from a single outlet, can lead to dis-
astrous consequences to home and family.
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