DVD-S325EE / DVD-S325GC / DVD-S325GCA / DVD-S325GCS / DVD-S325GCU
2 SAFETY PRECAUTIONS
2.1. GENERAL GUIDELINES
1. When servicing, observe the original lead dress. If a short circuit is found, replace all parts which have been overheated or
damaged by the short circuit.
2. After servicing, see to it that all the protective devices such as insulation barriers, insulation papers shields are properly
installed.
3. After servicing, make the following leakage current checks to prevent the customer from being exposed to shock hazards.
2.1.1. LEAKAGE CURRENT COLD2.1.2. LEAKAGE CURRENT HOT CHECK
CHECK(See Figure 1 .)
1. Unplug the AC cord and connect a jumper between the two 1. Plug the AC cord directly into the AC outlet. Do not use an
prongs on the plug.isolation transformer for this check.
2. Measure the resistance value, with an ohmmeter, between 2. Connect a 1.5k& , 10 watts resistor, in parallel with a 0.15?F
the jumpered AC plug and each exposed metallic cabinetcapacitors, between each exposed metallic part on the set
part on the equipment such as screwheads, connectors,and a good earth ground such as a water pipe, as shown in
control shafts, etc. When the exposed metallic part has aFigure 1.
return path to the chassis, the reading should be between 3. Use an AC voltmeter, with 1000 ohms/volt or more
1M& and 5.2M& .sensitivity, to measure the potential across the resistor.
When the exposed metal does not have a return path to the 4. Check each exposed metallic part, and measure the
chassis, the reading must be.
voltage at each point.
5. Reverse the AC plug in the AC outlet and repeat each of the
above measurements.
6. The potential at any point should not exceed 0.75 volts
RMS. A leakage current tester (Simpson Model 229 or
equivalent) may be used to make the hot checks, leakage
current must not exceed 1/2 milliamp. In case a
measurement is outside of the limits specified, there is a
possibility of a shock hazard, and the equipment should be
repaired and rechecked before it is returned to the
Figure 1customer.
3 PREVENTION OF ELECTRO STATIC DISCHARGE (ESD)
TO ELECTROSTATICALLY SENSITIVE (ES) DEVICES
Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components commonly are called
Electrostatically Sensitive (ES) Devices. Examples of typical ES devices are integrated circuits and some field-effect transistors and
semiconductor "chip" components. The following techniques should be used to help reduce the incidence of component damage
caused by electro static discharge (ESD).
1. Immediately before handling any semiconductor component or semiconductor-equipped assembly, drain off any ESD on your
body by touching a known earth ground. Alternatively, obtain and wear a commercially available discharging ESD wrist strap,
which should be removed for potential shock reasons prior to applying power to the unit under test.
2. After removing an electrical assembly equipped with ES devices, place the assembly on a conductive surface such as alminum
foil, to prevent electrostatic charge build up 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. Some solder removal devices not classified as "anti-static (ESD protected)" can
generate electrical charge 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 packaged with leads electrically shorted together by conductive foam, alminum foil or comparable
conductive material).
7. Immediately before removing the protective material from the leads of a replacement ES device, touch the protective material
to the chassis or circuit assembly into which the device will be installed.
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ACEC
