Panasonic DMP-BD77GA Service Manual - 1 Safety Precautions

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1 Safety Precautions

1.1.

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 essen-

tial that these critical parts should be replaced with manu-

facturer’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 acci-

dents resulting in personal injury from electrical shocks. It

will also protect AC Adaptor from being damaged by acci-

dental 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 over-

heated 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.

1.2.

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 metal-

lic cabinet part on the equipment such as screwheads,

connectors, control shafts, etc. When the exposed metal-

lic part has a return path to the chassis, the reading

should be between 1 M

Ω and 5.2 MΩ. When the exposed

metal does not have a return path to the chassis, the

reading must be infinity.

1.3.

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 1.5 k

Ω, 10 W resistor, in parallel with a 0.15 μF

capacitor, between each exposed metallic part on the set

and a good earth ground, as shown in Figure 1.

3. Use an AC voltmeter, with 1 k

Ω/V or more sensitivity, 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 V RMS.

A leakage current tester (Simpson Model 229 or equiva-

lent) may be used to make the hot checks, leakage cur-

rent must not exceed 1/2 mA. 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 customer.

Figure. 1