Hitachi 50gx49b Service Manual page 5

Read and comply with all caution and safety-related
notes on or inside the receiver cabinet, on the receiver
chassis, or on the picture tube.
Design Alteration Warning - Do not alter or add to
the mechanical or electrical design of this TV receiver.
Design alterations and additions including but not
limited to circuit modifications and the addition of
items such as auxiliary audio and/or video output
connectors, might alter the safety characteristics of
this receiver and create a hazard to the user. Any
design alterations or additions may void the
manufacturer's warranty and may make you, the
servicer, responsible for personal injury or property
damage resulting therefrom.
Picture Tube Implosion Protection Warning - The
picture tube in this receiver employs integral implosion
protection. For continued implosion protection,
replace the picture tube only with one of the same
type number. Do not remove, install, or otherwise
handle the picture tube in any manner without first
putting on shatterproof goggles equipped with side
shields. People not so equipped must be kept safely
away while picture tubes are handled. Keep the
picture tube away from your body. Do not handle the
picture tube by its neck.
5. Hot Chassis Warning - a. Some TV receiver chassis
are electrically connected directly to one conductor of
the AC power cord and may be safely serviced without
an isolation transformer only if the AC power plug is
inserted so that the chassis is connected to the
ground side of the AC power source. Confirm that the
AC power plug is inserted correctly with an AC
voltmeter by measuring between the chassis and a
known earth ground. If a voltage reading in excess of
1 .OV is obtained, remove and reinsert the AC power
plug in the opposite polarity and again measure the
voltage potential between the chassis and a known
earth ground. b. Some TV receiver chassis normally
have 85V AC (RMS) between chassis and earth
ground regardless of the AC plug polarity. These
chassis can be safely serviced only with an isolation
transformer inserted in the power line between the
receiver and the AC power source, for both personnel
and test equipment protection. c. Some TV receiver
chassis have a secondary ground system in addition
to the main chassis ground. This secondary ground
system is not isolated from the AC power line.The two
ground systems are electrically separated by
insulating material that must not be defeated or
altered.
6. Observe original lead dress. Take extra care to assure
correct lead dress in the following areas: a. near sharp
edges, b. near thermally hot parts-be sure that leads
and components do not touch thermally hot parts, c.
the AC supply, d. high voltage and e. antenna wiring.
Always inspect in all areas for pinched, out-of-plate, or
frayed wiring. Do not change spacing between
components and the printed circuit board. Check AC
power cord for damage.
Components, parts, and/or wiring that appear to have
overheated or are otherwise damaged should be
replaced with components, parts, or wiring that meet
original specifications. Additionally, determine the
cause of overheating and/or damage and, if
necessary, take corrective action to remove any
potential safety hazard.
PRODUCT SAFETY NOTICE - Many TV electrical
and mechanical parts have special safety-related
characteristics some of which are often not evident
from visual inspection, nor can the protection they
give necessarily be obtained by replacing them with
components rated for higher voltage, wattage, etc.
Parts that have special safety characteristics are
identified in Hitachi service data by shading on
schematics and by a A in the parts list. Use of
substitute replacement that does not have the same
safety characteristics as the recommended replace-
ment part in Hitachi service data parts list might
create shock, fire, and/or other hazards. Product
safety is under review continuously and new
instructions are issued whenever appropriate. For the
latest information, always consult the appropriate
current Hitachi service literature. A subscription to, or
additional copies of service literature may be obtained
at a nominal charge from Hitachi.
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