PRODUCT SAFETY SERVICING GUIDELINES FOR AUDIO-VIDEO PRODUCTS
3828VD0171G
i
DIGITAL FCS - SAFETY
IMPORTANT SAFETY NOTICE
This Manual was prepared for use only by prop-
erly trained audio-visual service technicians.
When servicing this product, under no circum-
stances should the original design be modified
or altered without permission from Zenith Elec-
tronics 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 completion of repairs.
Special components are also used to prevent x-
radiation, shock and fire hazard. These compo-
nents are indicated by the letter “x” included
in their component designators and are required
to maintain safe performance. Zenith Electron-
ics Corporation allows no deviations without
prior approval. Circuit diagrams may occasion-
ally 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 installa-
tions without manufacturer’s approval. Unautho-
rized modifications will not only void the war-
ranty, 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 equilat-
eral triangle is intended to alert the
service personnel to important safety
information in the service literature.
The lightning flash with arrowhead sym-
bol within an equilateral triangle is
intended to alert the service personnel
to the presence of non-insulated “dan-
gerous voltage” that may be of suffi-
cient magnitude to constitute a risk of
electric shock.
The pictorial representation of a fuse
and its rating within an equilateral tri-
angle is intended to convey to the ser-
vice personnel the following fuse re-
placement 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 trans-
ported 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 pos-
sible 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, an-
tenna 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 voltme-
ter having 5000 ohms per volt or more sensitiv-
ity in the following manner: Connect a 1500 ohm,
10 watt resistor, paralleled by .15 mfd 150V AC
type capacitor between a known good earth ground
(water pipe, conduit, etc.) and the exposed me-
tallic parts, one at a time. Measure the AC
voltage across the combination of 1500 ohm re-
sistor and .15mfd 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 poten-
tial shock hazard and must be corrected immedi-
ately.
A.C. Voltmeter
1500 OHM
10 WATT
Place this probe
on each exposed
metal part.
Good Earth Ground
such as the Water
Pipe, Conduit, etc.
0.15uF
X-RADIATION
1. Be sure procedures and instructions to all
service personnel cover the subject of x-ra-
diation. 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 sche-
matic. 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 lev-
els.
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 mea-
surements in a product with a problem of ex-
cessively high voltage, avoid being unneces-
sarily close to the picture tube and the high
voltage power supply. Do not operate the prod-
uct longer than necessary to locate the cause
of excessive voltage.
6. Refer to HV, B+, and shutdown adjustment
procedures described in the appropriate sche-
matics 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 leak-
age 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 fac-
tory-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 airflow 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.
