2 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, 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 1
M
Ω
and 5.2 M
Ω
. 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" to exposed metallic part on the set. And
connect "B" to 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
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 0.25 V RMS.
A leakage current tester (Simpson Model 228 or equivalent)
may be used to make the hot checks, leakage current 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
6
NV-GS6EE / NV-GS6GC / NV-GS17E / NV-GS17EB / NV-GS17EF / NV-GS17EG / NV-GS17EP / NV-GS18E / NV-GS21E / NV-GS21EB / NV-GS21EG / NV-GS21EK / NV-GS21EP / NV-GS25GC / NV-GS25GN /
GS28GK / NV-GS35E / NV-GS35EB / NV-GS35EG / NV-GS35EP / NV-GS35GC / NV-GS35GN / NV-GS38GK
