1-1
1. Precautions
Follow these safety,servicing and ESD precautions to prevent damage and protect against potential hazards such
as electrical shock and X-rays.
1-1 Safety Precautions
1) Be sure that all of the built-in protective devices are
replaced. Restore any missing protective shields.
2) When reinstalling the chassis and its assemblies, be
sure to restore all protective devices, including :
nonmetallic control knobs and compartment cov-
ers.
3) Make sure that there are no cabinet openings
through which people-particularly children-might
insert fingers and contact dangerous voltages.
Such openings include the spacing between the
picture tube and the cabinet mask, excessively
wide cabinet ventilation slots, and improperly
fitted back covers.
If the measured resistance is less than 1.0 megohm
or greater than 5.2 megohms, an abnormality exists
that must be corrected before the unit is returned
to the customer.
4) Leakage Current Hot Check(Fig. 1-1):Warning:Do
not use an isolation transformer during this test.
Use a leakage-current tester or a metering system
that complies with American National Standards
Institute(ANSI C101.1, Leakage Current for
Appliances),and Underwriters Laboratories(UL
Publication Ul1410, 59.7).
Fig. 1-1 Leakage Test
5) With the unit completely reassembled, plug the AC
line cord directly the power outlet. With the unit’s
AC switch first in the ON position and the OFF,
measure the current between a known earth
ground(metal water pipe,conduit,etc.)and all
exposed metal parts, including:antennas, handle
brackets,metal cabinets,screwheads and control
shafts. The current measured should not exceed
0.5milliamp. Reverse the power-plug prongs in the
AC outlet and repeat the test.
6) Antenna Cold Check:
With the unit’s AC plug disconnected from the AC
source, connect an electrical jumper across the two
AC prongs. Connect one lead of the ohmmeter to
an AC prong. Connect the other lead to the coaxial
connector.
7) X-ray Limits:
The picture tube is especially designed to prohibit
X-ray emissions. To ensure continued X-ray protec-
tion, replace the picture tube only with the one that
is the same type as the original. carefully reinstall
the picture tube shields and mounting
hardware;these also provide X-ray protection.
8) High Voltage Limits:
High voltage must be measured each time servic-
ing is done on the B+,horizontal deflection or high
voltage circuits. Correct operation of the x-ray pro-
tection circuits must be reconfirmed whenever they
are serviced. (X-ray protection circuits also may be
called “horizontal disable” or “hold-down”.)
Heed the high voltage limits. These include the X-
ray protection Specifications Label, and the
Product Safety and X-ray Warning Note on the ser
vice data schematic.
9) High voltage is maintained within specified limits
by close tolerance, safety-related components and
adjustments. If the high voltage exceeds the speci-
fied limits, check each of the special components.
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