Safety Precautions - Panasonic Palmcorder VHSC PalmSight PV-L759 Service Manual

SAFETY PRECAUTIONS

GENERAL GUIDELINES
1. IMPORTANT SAFETY NOTICE
There are special components used in this equipment
which are important for safety. These parts are marked by
in the Schematic Diagrams, Circuit Board Layout,
Exploded Views and Replacement Parts List. It is essential
that these critical parts should be replaced with
manufacturer's specified parts to prevent X-RADIATION,
shock, fire, or other hazards. Do not modify the original
design without permission of manufacturer.
2. An Isolation Transformer should always be used during the
servicing of AC Adaptor whose chassis is not isolated from
the AC power line. Use a transformer of adequate power
rating as this protects the technician from accidents resulting
in personal injury from electrical shocks. It will also protect
AC Adaptor from being damaged by accidental shorting
that may occur during servicing.
3. 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.
4. After servicing, see to it that all the protective devices
such as insulation barriers, insulation papers shields are
properly installed.
5. After servicing, make the following leakage current
checks to prevent the customer from being exposed to
shock hazards.
LEAKAGE CURRENT COLD CHECK
1. Unplug the AC cord and connect a jumper between the two
prongs on the plug.
2. Measure the resistance value, with an ohmmeter, between
the jumpered AC plug and each exposed metallic cabinet
part on the equipment such as screwheads, connectors,
control shafts, etc. When the exposed metallic part has a
return path to the chassis, the reading should be between
1M ohm and 5.2M ohm. When the exposed metal does not
have a return path to the chassis, the reading must be
infinity.
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 1.5k ohm, 10 watts resistor, in parallel with a
0.15 micro farad capacitor, between each exposed metal-
lic part on the set and a good earth ground, as shown in
figure 1.
3. Use an AC voltmeter, with 1000 ohms/volt or more sensi-
tivity, to measure the potential across the resistor.
4. Check each exposed metallic part, and measure the volt-
age 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 measure-
ment 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 customer.
Hot-Check Circuit
AC VOLTMETER
TO
APPLIANCES
EXPOSED
METAL PARTS
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 follow-
ing techniques should be used to help reduce the incidence of
component damage caused by electro static discharge (ESD).
1. Immediately before handling any semiconductor compo-
nent 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 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 antistatic solder removal device. Some solder
removal devices not classified as "antistatic (ESD pro-
tected)" can generate electrical charge sufficient to dam-
age 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, aluminum
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.
CAUTION :
Be sure no power is applied to the chassis or circuit, and
observe all other safety precautions.
8. Minimize bodily motions when handling unpackaged re-
placement ES devices. (Otherwise harmless motion such
as the brushing together of your clothes fabric or the lifting
of your foot from a carpeted floor can generate static
electricity (ESD) sufficient to damage an ES device).
1-1
0.15µF
EARTH GROUND
1500Ω. 10W
Figure. 1