SAFETY PRECAUTIONS
GENERAL GUIDELINESELECTROSTATICALLY SENSITIVE (ES) DEVICES
1. When servicing, observe the original lead dresSome s. If a semicshorondutctor (solid state) devices can be damaged
circuit is found, replace all parts which haveeasi beeln ovy byer- static electricity. Such components commonly are
heated or damaged by the short circuit.called Electrostatically sensitive (ED) Devices. Examples of
2. After servicing, see to it that all the prottyectpicalive dev ES devicesices are integrated circuits and some field-
such as insulation barriers, insulation papers efshiefect trlds ansareistors and semiconductor ?chip? components. The
properly installed.following techniques should be used to help reduce the
3. After servicing, make the following leakage incicurrdence entof component damage caused by static electricity.
checks to prevent the customer from being exposed to
shock hazards.1. Immediately before handling any semiconductor
component or semiconductor-equipped assembly, drain
LEAKAGE CURRENT COLD CHECKoff any electrostatic charge on your body by touching a
known earth ground.
1. Unplug the AC cord and connect a jumper between the
Alternatively, obtain and wear a commercially available
two prongs on the plug.
discharging wrist trap device, which should be removed
2. Measure the resistance value, with an ohm meter,
for potential shock reasons prior to applying power to the
between the jumpered AC plug and each exposed
unit under test.
metallic cabinet part on the equipment such as
2. After removing an electrical assembly equipped with ES
screwheads, connectors, control shafts, etc. The
devices, place the assembly on a conductive surface
resistance value must be more th&. an 5M
such as aluminum foil, to prevent electrostatic charge
buildup or exposure of the assembly.
3. Use only a grounded tip soldering iron to solder or
unsolder ES devices.
4. Use only an anti-static solder removal device classified as
?anti-static? can generate electrical charges sufficient to
damage ES devices.
5. Do not use freon-propelled chemicals. These can
generate electrical charges sufficient to damage ES
devices.
6. Do not remove a replacement ES device from its
protective package until immediately before you are
ready to install it.
(most replacement ES devices are package with leads
Figure1electrically shorted together by conductive foam,
aluminum foil or comparable conductive material).
7. Immediately before removing the protective material from
the leads of a replacement ES device, touch the
LEAKAGE CURRENT HOT CHECK (See Figure 1)
protective material to the chassis or circuit assembly into
1. Plug the AC cord directly into the AC outlet.which the device will be installed.
Do not use an isolation transformer for this check.CAUTION : Be sure no power is applied to the chassis or
2. Connect a 1.5k& , 10W resistor, in parallel with a 0.1circ5?uit, and observe all other safety precautions.
F capacitor, between each exposed metallic part 8. oMni nimizthee bodily motions when handling unpacked
set an a good earth ground such as a water piperepla, ascement ES devices. (Otherwise harmless motion
shown in Figure1.such as the brushing together of your clothes fabric or the
3. Use an AC voltmeter, with 1000 ohms/volt or liftimoreng of your foot from a carpeted floor can generate
sensitivity, to measure the potential across the rstatiesistorc e.lectricity sufficient to damage an ES device).
4. Check each exposed metallic part, and measure the
voltage at each point.X-RADIATION
5. Reverses the AC plug in the AC outlet repeat each of the
WARNING
above measurements.
1.The potential source of X-radiation in EVF sets is the
6. The potential at any point should not exceed 0.15 volts
High Voltage section and the picture tube.
RMS. A leakage current tester (Simpson Model 229
2. When using a picture tube test jig for service, ensure that
equivalent) may be used to make the hot checks, leakage
jig is capable of handling 10kV without causing x-
current must not exceed 0.1 milliamp. In case a
measurement is outside of the limits specified, thradiatere is ion.a
possibility of a shock hazard, and the equipmeNotent shou :It ldis important to use an accurate periodically
calibrated high voltage meter.
be repaired and rechecked before it is returned to the
3. Measure the High Voltage. The meter (electric type)
customer.
reading should indicate ? 2.5kV, 0.15kV. If the meter
indication is out of tolerance, immediate service and
correction is required to prevent the possibility of
premature component failure. To prevent an x-radiation
possibility, it is essential to use the specified picture tube.
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ACEC
