Safety Precautions - Hitachi UT42X902/D8MW Service Manual

SAFETY PRECAUTIONS

NOTICE: Comply with all cautions and safety-related notes
located on or inside the cover case and on the chassis or
LCD module.
WARNING: Since the chassis of this receiver is connected
to one side of the AC power supply during operation,
whenever the receiver is plugged in service should not
be attempted by anyone unfamiliar with the precautions
necessary when working on this type of receiver.
1. When service is required, an isolation transformer
should be inserted between power line and the receiver
before any service is performed on a "HOT" chassis
receiver.
2. When replacing a chassis in the receiver, all the
protective devices must be put back in place, such as
barriers, nonmetallic knobs, insulating cover-shields,
and isolation resistors, capacitors, etc.
3. When service is required, observe the original lead
dress (wiredress).
4. Always use manufacturer's replacement components.
Critical components as indicated on the circuit diagram
should not be replaced by another manufacturer's.
Furthermore, where a short circuit has occurred,
replace those components that indicate evidence of
over heating.
5. Before returning a serviced receiver to the customer,
the service technician must thoroughly test the unit to
be certain that it is completely safe to operate without
danger of electrical shock, and be sure that no protective
device built into the receiver by the manufacturer has
become defective, or inadvertently defeated during
servicing.
Therefore, the following checks should be performed
for the continued protection of the customer and service
technician.
Leakage Current Cold Check
With the AC plug removed from the 120V AC 60Hz source,
place a jumper across Line 1 and Line 2 of the three plug
prongs, do not connect with the third prong, which is
physical ground.
Using an insulation tester (DC500V), connect one of its
leads to the AC plug jumper and touch with the other lead
each exposed metal part (antennas, screwheads, metal
overlays, control shafts, etc.), particularly any exposed
metal part having a return path to the chassis should
have a resistor reading over 4MΩ. Any resistance value
below this range indicates an abnormality which requires
corrective action. An exposed metal part not having a
return path to the chassis will indicate an open circuit.
TABLE OF CONTENTS
Leakage Current Hot Check
Plug the AC line cord directly into a 120V AC outlet. (Do
not use an isolation transformer during this test.) Use a
leakage current tester or a metering system that complies
with the American National Standards Institute (ANSI)
C101.0 Leakage Current for Appliances. In the case of
the LCD monitor set the AC switch first in the ON posi-
tion and then in the OFF position, measure from across
Line 1 and Line 2 of the three plug prongs (do not con-
nect with the third prong which is physical ground), to
all exposed metal parts of the instrument (antennas,
handle bracket, metal cabinet, screw heads, metallic
overlays, control shafts, etc.), especially any exposed
metal parts that offer an electrical return path to the chassis.
Any current measured must not exceed 0.5 MIU. Reverse
the instrument power cord plug in the outlet and repeat test.
AC LEAKAGE TEST
(USING ADAPTER AS
REQUIRED)
ANY MEASUREMENTS NOT WITHIN THE LIMITS
OUTLINED ABOVE ARE INDICATIVE OF A POTENTIAL
SHOCK HAZARD AND MUST BE CORRECTED BEFORE
RETURNING THE RECEIVER TO THE CUSTOMER.
NOTE:
Unplug the AC cord from the power
line before servicing the LCD TV
set.
The Main Power Switch does not
completely cut the AC power.
2
D8MW