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PRODUCT SAFm SERVICING GUIDELINES FOR COLOR TELEVISION RECEIVERS
CAUTION: No modification
of
any circuit should be attamptad.
Setvica work should be parformed only aftar you .re thoroughly
familiar with all
of
the following safety checks and sarvicing guidelines.
To do otherwise increlSlS the risk of potential hazards and injury to the
user.
SAFETY CHECKS
Aftar the original servica problem has been correctad, • check should be
made of the following:
SUBJECT: FIRE • SHOCK HAZARD
1. Ba sure that.1I components are positioned in such a way as to avoid
possibility of adjacant component shorts. This is especially impor·
tant on thosa chassis which are trensported to and from the repair
shop.
2. Never releasa a repair unless all protactive devices such as insulators,
barriers, covers, shields, strain reliefs, and other hardware heve been
reinstalled per original design.
3. Soldaring must be inspectad to discover possible cold solder joints,
freyed leads, damaged insulation (including AC cord), solder
splashes or sharp solder points. Be certein to remove all loose
foreign particles.
4. Check the "across-tha-line" capacitor and other components for
physical evidence of damage or deterioration and replace if
nlClssary. Follow original layout, lead length and dress.
5. No lead or component should touch a receiving tube or a resistor
reted at 1 watt or more. Lead tension around protruding metel
surtacas must be evoided.
6. All critical components (shaded on the schematic diagrem and parts
lists) such as fuses, flameproof resistors, capacitors, ate, must be
replacad with exact Zenith types. Do not use replacemant compo·
nents other than those specified or make unrecommended circuit
modifications.
7. Aftar rHssambly of the set always perform an AC leakage test on
all exposed metallic parts of the cabinet, (the channel selector
knobs, antenna terminals, h.ndle and screws) to be sure the sat is
safe to operata 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 sansitivity, in the
following m.nner; Connect a 1500 ohm 10 watt resistor
(63·10401·76), parelleled by a .15 rnfd. 150V AC type cap.citor
(22-43841 between a known good earth ground (water pipe,
conduit, etc.land the exposed metallic parts, one at a time. Measure
the AC voltage across the combination 1500 ohm resistor and .15
mfd. capacitor. Reverse the AC plug and repeat AC voltage
measurements for each expllSld metallic part. Voltage measured
must not excead .75 volts RMS. This corresponds to 0.5 milliamp
AC. Any value exceeding this limit constitutes. potential shock
hazard and must be corrected immedi.tely.
TO GOOD EARTH GROUND
SUCH
NI.
WATER "PE.
COIIOUIT. ETC.
SUBJECT: IMPLOSION
I~I
o
A.C. VOLTMETER
0
22-4314
. ISMFO
A.C. TYPE
PLACE THIS PROBE
ON EACH EXPOSED
METALLIC PART.
1.
All Zenith picture tubes are equipped with .n integrel implosion
protection syStlm, but care should be taken to avoid damage during
install.tion. Avoid scr.tching the tube.
2. U. only recomrr.ended Zenith replacement tubes.
SUBJECT: X·RADIATION
1. Be sure procedum and instructions to .11 sarvice personnel cover
the subject of X·radi.tion. The only potential sourca of X·rays in
current TV receivers is the picture tube.
~owaver,
this tube dOls not
I",it X·reys when the H. V. is at tha factory specified level. It is only
whln thl H. V. is excassivl that X·rediation may
be
generated. Refar
to the X·rey Precaution Label which is locatad inside each talevision
receiver for the correct high voltage. The proper value is also givan
in the applicable servica manual. Operetion at higher voltages
may
cause • failure of the picture tube or high v.oltage supply and, under
cart.in circumstances, may produce radiation in excess of desirebll
levels.
2. Only Zenith specified CRT anode connectors must be usad. The
degaussing shield also serves as an X·ray shield in color sats, do not
defeat its purpose.
3. I t is essential that the serviceman has .v.il.ble an .ccurate and
reliable high voltage meter. The calibration of the meter should be
checked periodically against a refarenca standard, such as the one
aveilable lit your distributor.
4. When the high voltage circuitry is opereting properly there
is
no
possibility of an X·radiation problem. Every time a color chassis
is
seniicad, the brightness should be run up and down while
monitoring the high voltage with a meter to be certain that the high
voltage dOls not exceed the specified value and that it is regulating
correctly. We suggest that you and your service organization review
test procedures so that voltage regulation is always checked as a
st.ndard servicing procedure, and that the high voltage reading be
recorded on each customer's invoice.
5. When trouble shooting and making tast measurements in a receivar
with a problem of excessive high voltage, avoid being unnecassarily
close to the picture tube and the high voltage compartment. 00 not
operate the chassis longer th.n is necessary to loc.ta the cause of
excassive voltage.
6. Color transistor sets manufactured after June, 1973 ("E" Lina and
laterl, use new type picture tubes specific.lly designed to withstand
higher operating voltages without causing excessive X .... di.tion. It is
strongly recommended that the C.R.T. shop fixture be equipped
with the new type tube. Addition of a permanently connected H.V.
meter to the H.V. anode of the shop C.R.T. fixture isadviseble. The
C. R. T:s in these sets should never
be
replaced with any other tube
types
8S
that may result in excessive X·radiation and possible
violation of the law.
7. Starting with late production "E" line color sets, • special four lead
damper capacitor was used. Its feature, the interlocking four leads,
should not be defeatad. However, each time one of these sets is
serviced, for whatever reason, the part number of the capacitor
should be examined. If it is the 22·7233 typa (used in "E" and "F"
model lines onlyl, that capacitor must be replaced with an improved
recommendad type (22-7504.(11). Please refer to Zenith Tech
Topics tissue No. 87) for the datails. Your distributor will answer
any questions, or you may write to Zenith for further details.
SUBJECT: TIPS DN PRDPER INSTALLATIDN
1. Never install any receiver in a closed·in recess, cubbyhole or closely
fitting shelf space.
2. Never install a receiver over, or close to a heat duct, or in the path
of heated air flow.
3. Avoid conditions of high humidity such
a;
outdoor patio installa·
tions whare dew
is
a factor, near steam radiators where ltaam
leakage ill factor, atc .
4. Avoid placement whera drlperies may obstruct rear venting. The
customer should .Iso avoid the use of decorative scarves or other
coverings which might obstruct ventilation.
5. Wall and shelf mounted installations using a commercial mounting
kit, must follow the factory approved mounting instructions.
6. A receiver mountad to a shelf or platform must ratain its origillli
feet (or the equivelent 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 customizad
installations.
7. Caution customers against the mounting of • receiver on a sloping
shelf or in a tilted position, unless the receivar is properly secured.
8. A receiver in a roll .. bout cart should be steble in its mounting to the
cart. Caution the customer on the hazards of trying to roll. cart
with small casters across thresholds or deep pile carpets.
9. Caution customers against the use of a cart or stand which has not
been listed byUnderwritars Laboratorias, Inc. for use with their
specific modal of talevision receiver.
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