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'19SV111
IMPORTANT SERVICE SAFETY PRECAUTION
• Service w_ork should be performed only
by
qualified service technicians who are
thoroughly familiar with all safety checks and servicing guidelines which follow:
WARNING
1. For continued safety, no modification of any
circuit should be attempted.
2. Disconnect AC power before servicing.
3. Semiconductor heat sinks are potential shock
hazards when the receiver is operating.
4. The chassis in this receiver has two ground
systems which are separated by insulation
material. The non-isolated (hot) ground system
is for the + B voltage regulator circuit and the
horizontal output circuit. The isolated ground
sy5tem is for the low + B DC voltages and the
secondary circuit of the high voltage
transformer.
To prevent electrical shock use an isolation
transformer between the I i ne cord and power
receptacle, when servicing this chassis.
SERVICING OF HIGH VOLTAGE
SYSTEM
AND
PICTURE TUBE
When servicing the high voltage system,
remove the static charge by connecting a
10k ohm resisto-r in series with an
insulated wire (such as a test probe)
between the picture tube ground and
the anode lead. {AC cord should be
disconnected from AC outlet.)
1. Note that the picture tube in this receiver
employs integral implosion protection.
2. Replace with tube of the same type number for
continued safety.
3. Do not I i
ft
picture tube by the neck.
4. Handle the picture tube only when wearing
shatterproof goggles and after discharging the
high voltage anode completely.
X-RADIATION AND HIGH VOLTAGE
LIMITS
1. All service personnel should be aware of the
procedures and instructions covering X-
radiation. The only potential source of X-ray in
current solid state TV receivers is the picture
tube. However, the picture tube does not emit
measurable X-Ray radiation if the high voltage
is as specified in the "High Voltage Check"
instructions.lt is only when high voltage is
excessive that X·rad iation is capable of
penetrating the picture tube shell which
includes lead in glass material. The important
precaution is to keep high voltage below the
maximum level specified.
2
2. It is essential that servicemen have available at
all times an accurate high voltage meter. The
calibration of this meter should be checked
periodically.
3. High voltage should always be kept at the
rated value -no higher. Operation at higher
voltages may cause a failure of the picture tube
or high voltage circuitry and, under certain
conditions, may produce radiation in excess of
desirable levels.
4. When the high voltage regulator is operating
properly there is no possibility of an X-
radiation problem. Every time a color chassis is
serviced, the brightness should be tested
while monitoring high voltage with a meter to
be certain that it does not exceed the specified
value and is regulated correctly.
5. Do not use a picture tube other than that
specified, and do not make unrecommended
circuit modifications to the high voltage
circuitry.
6. When trouble shooting and taking test
measurements on a receiver with excessively
high voltage,avoid being unnecessarily dose to
the receiver. Do not operate the receiver
longer than is necessary to locate the cause of
excessive voltage.
FIRE
AND SHOCK HAZARD CHECKS
Before returning the receiver to the user,
perform the following safety checks:
1. Inspect all lead dress to make certain that leads
are not pinched, and check that hardware is
not lodged between the chassis and other
metal parts in the receiver.
2. Inspect all protective devices such as non·
metallic control knobs, insulating materials,
cabinet backs, adjustment and compartment
covers or shields, isolation resistor-capacity
networks, mechanical insulators, etc.
3. To be sure that no shock hazard exists, check
for current I eakage in the foil owing manner:
• PI ug the AC cord d i recti y into a 120 volt AC
outlet, (Do not use an isolation transformer for
this test).
• Using two clip leads, connect a 1.5k ohm, 10
watt resistor paralleled by a 0.1SuF capacitor in
series with all exposed metal cabinet parts and
a known earth ground, such as an electrical
conduit or electrical ground connected to an
earth ground.
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