Zenith P42W34, Service Manual

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IMPORTANT SAFETY NOTICE
This manual was prepared for use only by properly trained audio-visual service
technicians.
When servicing this product, under no circumstances should the original 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 location, wiring and lead dress must conform
to original layout upon completion of repairs.
CAUTION: Do not attempt to modify this product in any way.
Never perform customized installations without manufacturer’s
approval.
Unauthorized modifications will not only void the warranty, but may
lead to property damage or user injury.
Service work should be performed only after you are thoroughly familiar with
these safety checks and servicing 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 personnel to the presence
of noninsulated “dangerous voltage” that may be of sufficient
magnitude to constitute a risk of electric shock.
The pictorial representation of a fuse and its rating within an
equilateral triangle is intended to convey to the service personnel
the following fuse replacement caution notice:
CAUTION: FOR CONTINUED PROTECTION AGAINST RISK
OF FIRE, REPLACE ALL FUSES WITH THE 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, covers, shields,
strain reliefs, power supply cords, and other hardware have been reinstalled
per the original design. Be sure that the safety 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 receiving tube or a resistor 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 ISOLATION
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, conduit, 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 metallic part.
Voltage measured must not exceed 0.75 volts RMS. This corresponds 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 installations where
dew is a factor, near steam radiators where steam leakage is a factor, etc.
3. Avoid placement where draperies may obstruct venting. The customer
should also avoid the use of decorative scarves or other coverings that might
obstruct ventilation.
4. Wall- and shelf-mounted installations using a commercial mounting kit must
follow the factory-approved mounting instructions. A product 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 disastrous
consequences to home and family.
A V
PRODUCT SAFETY GUIDELINES
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