Safety Instructions - Sanyo DP19640 Service Manual

SAFETY INSTRUCTIONS

SAFETY PRECAUTIONS
WARNING: The chassis of this receiver has a floating
ground with the potential of one half the AC line voltage
in respect to earth ground. Service should not be
attempted by anyone not familiar with the precautions
necessary when working on this type of equipment.
The following precautions must be observed:
1. An isolation transformer must be connected in the
power line between the receiver and the AC line
before any service is performed on the receiver.
2. Comply with all caution and safety-related notes
provided inside the cabinet, on the chassis, and
on the back.
3. When replacing a chassis in the cabinet, always
be certain that all the protective devices are installed
properly, such as control knobs, adjustment covers,
shields and barriers.
4. Before replacing the back cover of the set, thoroughly
inspect the inside of the cabinet to see that no stray
parts or tools have been left inside. Before returning
any television to the customer, the service technician
must perform the following safety checks to be sure
that the unit is completely safe to operate without
danger of electrical shock.
ANTENNA COLD CHECK
Remove AC plug from the 120 VAC outlet and place
a jumper across the two blades. Connect one lead
of an ohmmeter to the jumpered AC plug, and touch
the other lead to each exposed antenna terminal
(UHF and VHF antenna terminals). The resistance
must measure between 1M ohm and 5.2M ohm. Any
resistance value below or above this range indicates
an abnormality which requires corrective action.
LEKAGE GURRENT CHECK
Plug the AC line cord directly into a 120 VAC outlet.
(Do not use an isolation transformer for this check.)
Use an AC voltmeter, that has 5000 ohms per volt or
more sensitivity. Connect a 1500 ohm 10 watt resistor,
paralleled by a 0.15 μF 150 VAC capacitor, between
a known good earth ground (water pipe, conduit, etc.)
and all exposed metal parts of the cabinet (antennas,
handle bracket, metal cabinet, screw heads, metal
overlays, control shafts, etc.). Measure the AC voltage
across the 1500 ohm resistor. The AC voltage should
not exceed 750 mV. A reading exceeding 750 mV
indicates that a dangerous potential exists. The fault
must be located and corrected. Repeat the above test
with the receiver power plug reversed.
NEVER RETURN A RECEIVER TO THE CUSTOMER
WITHOUT TAKING THE NECESSARY CORRECTIVE
ACTION.
PRODUCT SAFETY NOTICE
When replacing components in a receiver, always keep
in mind the necessary product safety precautions.
Pay special attention to the replacement of components
marked with a in the parts list and in the schematic
diagrams. To ensure safe product operation, it is
necessary to replace those components with the
exact same PARTS.
SERVICING ELECTROSTATICALLY
SENSITIVE DEVICES
Semiconductors (solid-state devices) that can be
damaged by static electricity are referred to as
Electrostatically Sensitive (ES) devices. Examples of
typical ES devices are: Integrated Circuits (IC), Field-
Effect Transistors (FET), and "chip" components.
The following techniques should be observed strictly,
to reduce the occurrence of semiconductor damage
due to electrostatic discharge.
1. Immediately prior to handling any semiconductor
component or an assembly containing a semiconductor
device or devices, discharge the electrostatic
buildup on your body by touching a known earth
ground. You may also obtain and wear a commercially
available discharging wrist strap device.
CAUTION: Be sure to remove the wrist strap before
applying power to any unit being serviced.
2. After removing an ES equipped assembly, place it
on a conductive surface, such as, aluminum foil,
to prevent buildup or exposure to static electricity.
3. Use only grounded-tip soldering irons to solder or
unsolder ES devices.
4. Use only anti-static solder removal devices. Some
suction-type devices can generate static electricity
adequate to damage ES devices.
5. A replacement ES device will come packaged in
protective material (conductive foam, aluminum
foil, or some comparable conductive material). Do
Not remove an ES device from its protective
packaging unless you are prepared to install it
immediately.
6. Precisely prior to removing an ES device from its
protective packaging, touch the protective
packaging to the chassis or assembly in which the
device will be installed.
CAUTION: Be sure that no power is applied to the
chassis or circuit assembly.
7. Incidental body movements, such as, lifting a foot
from a carpeted floor or the rubbing of fabric together
can generate static electricity sufficient to damage
ES devices. Therefore, minimize all body movements
while handling exposed (unpackaged) ES devices.
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