PV151
1-2
PROJO
GENERAL INFORMATION
IMPORTANT SAFETY NOTICE
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.
Special components are also used to prevent x-radiation, shock and fire hazard.
These components are indicated by the letter x included in their component
designators and are required to maintain safe performance. 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 manufacturers 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 re-assembly 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.
X-RADIATION
1. Be sure procedures and instructions to all service personnel cover the subject of
x-radiation. The only potential source of x-rays in current TV receivers is the
picture tube. However, this tube does not emit x-rays when the HV is at the
factory-specified level. The proper value is given in the applicable schematic.
Operation at higher voltages may cause a failure of the picture tube or high-
voltage supply and, under certain circumstances, may produce radiation in excess
of desirable levels.
2. Only factory-specified CRT anode connectors must be used.
3. It is essential that the service personnel have available an accurate and
reliable high-voltage meter.
4. When the high-voltage circuitry is operating properly, there is no possibility
of an x-radiation problem. Every time a color chassis is serviced, the
brightness should be run up and down while monitoring the high voltage
with a meter, to be certain that the high voltage does not exceed the
specified value and that it is regulating correctly.
5. When troubleshooting and making test measurements in a product with a
problem of excessively high voltage, avoid being unnecessarily close to
the picture tube and the high voltage power supply. Do not operate the
product longer than necessary to locate the cause of excessive voltage.
6. Refer to HV, B+, and shutdown adjustment procedures described in the
appropriate schematics and diagrams (where used).
IMPLOSION
1. All direct view picture tubes are equipped with an integral implosion
protection system; take care to avoid damage during installation.
2. Use only the recommended factory replacement tubes.
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.
PRODUCT SAFETY SERVICING GUIDELINES FOR AUDIO-VIDEO PRODUCTS
A.C. Voltmeter
1600 OHM
10 WATT
Place this probe
on each exposed
metal part.
Good Earth Ground
such as the Water
Pipe, Conduit, etc.
0.16uF
