Panasonic AG-MD830E - Page 3

SAFETY PRECAUTIONS
GENERAL GUIDELINES
1. When servicing observe the original lead dress. If a short
circuit isfound, replac all parts which have been overheated
or damaged by the short circuit.
2 . After servici ng, see to it that a II the protectiv 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 bei ng exposed to shock
hazards.
LEAKAGE CURRENT COLD CHECK
1. Unplug the AC cord and connect a jumper between the two
prongs onthe plug.
2. Measur the resistance value, with an ohm meter, between
the
jumpered AC plug and each exposed metallic cabinet
part on the equipment such as screwhead connectors, contrl
shafts, etc. When the exposed metallic part has a return
path to the chassis, the reading shoulb be between 1 M Q
and 5.2MQ.
When the exposed metal dose not have a return path to the
chassis, the read i ng m ust be 00 .
AC VOLTMETER
Hot-Check Circuit
TO
APPLIANCE'S
EXPOSED
METAL PARTS
0.15,u F
Figure 1
COLD
WATER PIPE
(EARTH GROUND)
LEAKAGE CURRENT HOT CHECK (See Figure 1)
1. Plug the AC cord directly into the AC outlet.
Do not use an isolation transformer for this check.
2. Connect a 1.5KQ, 10W resistor, inparallel with 0.15,u F
capacitor, between each exposed metallic part on the set an
a
good earth grou'nd such as a water pipe, as shown in
Figure 1.
3. Use an AC voltmeter, with 1000 ohms/volt or more
sensitivity, to measur the potential across the resistor.
4. Check each exposed metallic part, and measure the voltage
at each poi nt.
5. Reverse the AC plug in the AC outlet repeat each of the
above measurements.
6. The potantial at any point should not exceed 0.75 volts
RMS. A leakage current tester (Simpson Model 229
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
possiblity of a shock hazard, and the equipment should be
repa i red and rechecked before it is returned to the
customer.
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 static electricity.
1. Immediately before handling any semiconductor
component or semiconductor-equipped assembly, drain off
any electrostatic charge on your body by touching a known
earth ground.
Alternatively, obtain and wear a commercially available
discharging wrist strap device, 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
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 untilimmediately before you are ready to install
it. (most replacement ES devices are packaged with leads
electrically shorted together by conductive foam,
aluminum foil or comparable conductive material).
7. Immediately before removing the protective material from
the leads of replacement ES device, touch the protective
material to the chassis or circuit assembly into which the
device
will be installed.
CAUTION: Be sure no power is applied to the chassis or
circuit, and observe all otner asfety precautions.
8. Minimize bodily motions when handling unpackaged
replacement ES devoces. (Otherwise harm less mother such
as the
brushing together of your clothes fabric or the lifting
of your foor from a carpeted floor can generate static
electricity sufficient to damage an ES device).
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