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IMPORTANT SERVICE SAFETY INFORMATION
Operating the receiver outside of its cabinet or with its
back removed involves a shock hazard. Work on
these models should only be performed by those who
are thoroughly familiar with precautions necessary
when working on high voltage equipment.
Exercise care when servicing this chassis with power
applied. Many B plus and high voltage RF terminals are
exposed which, if carelessly contacted, can cause
serious shock or result in damage to the chassis.
Maintain interconnecting ground lead connections
between chassis, escutcheon, picture tube dag and
tuner cluster when operating the chassis.
These receivers have a "polarized" AC line cord. The AC
plug is designed to fit into standard AC outlets in one
direction only. The wide blade connects to the "ground
side" and the narrow blade connects to the "hot side" of
the AC line. This assures that the TV receiver is properly
grounded to the house wiring. If an extension cord must
be used, make sure it is of the "polarized" type.
Since the chassis of this receiver is connected to one
side of the AC supply during operation, service should
not be attempted by anyone not familiar with the
not be attempted by anyone not familiar with the
precautions necessary when working on these types
of equipment.
When it is necessary to make measurements or tests with
AC power applied to the receiver chassis, an Isolation
Transformer must be used as a safety precaution and to
prevent possible damage to transistors. The Isolation
Transformer should be connected between the TV line
cord plug and the AC power outlet.
When removing springs or spring mounted parts from the
tuner, tuner cluster or chassis, shatterproof goggles must
be worn. Keep others without shatterproof goggles away.
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 or that hardware is not lodged between
the chassis and other metal parts in the receiver.
2. Replace all protective devices such as nonmetallic
control knobs, insulating fishpapers, cabinet backs,
adjustment and compartment covers or shields,
isolation resistor-capacitor networks, mechanical
insulators, etc.
3. To be sure that no shock hazard exists, a check for
the presence of leakage current should be made at
each exposed metal part having a return path to the
chassis (antenna, cabinet metal, screw heads,
knobs and/or shafts, escutcheon, etc.) in the
following manner.
Plug the AC line cord directly into a 120V AC receptacle.
(Do not use an Isolation Transformer during these
checks.) All checks must be repeated with the AC line
cord plug connection reversed. (If necessary, a
nonpolarized adapter plug must be used only for the
purpose of completing these checks.)
If available, measure current using an accurate leakage
If available, measure current using an accurate leakage
current tester. Any reading of 0.35mA or more is
excessive and indicates a potential shock hazard which
must be corrected before returning the receiver to the
owner.
If a reliable leakage current tester is not available, this
alternate method of measurement should be used.
Using two clip leads, connect a 1500 ohm, 10 watt
resistor paralleled by a 0.15µF capacitor in series with
a known earth ground, such as a water pipe or conduit
and the metal part to be checked. Use a VTVM or
VOM with 1000 ohms per volt, or higher, sensitivity to
measure this AC voltage drop across the resistor. Any
reading of 0.35 volt RMS or more is excessive and
indicates a potential shock hazard which must be
corrected before returning the receiver to the owner.
TO EXPOSED
METAL PARTS
A1-1
A1-1
VT VM
AC SCALE
0.15K OHMS
10W
10µF
TO KNOWN
TEST PROBE
EARTH GROUND
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