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Extracted text from Hitachi DVP 305 U Service Manual (Ocr-read)
Page 1
1-1
1. Precautions
1-1 Safety Precautions
1) Before returning an instrument to the customer,
always make a safety check of the entire
instrument, including, but not limited to, the
following items:
(1) Be sure that no built-in protective devices are
defective or have been defeated during servicing.
(1)Protective shields are provided to protect both
the technician and the customer. Correctly replace
all missing protective shields, including any
remove for servicing convenience.
(2)When reinstalling the chassis and/or other as-
sembly in the cabinet, be sure to put back in place
all protective devices, including, but not limited to,
nonmetallic control knobs, insulating fish papers,
adjustment and compartment covers/shields, and
isolation resistor/capacitor networks. Do not
operate this instrument or permit it to be operated
without all protective devices correctly installed
and functioning.
(2) Be sure that there are no cabinet openings through
which adults or children might be able to insert
their fingers and contact a hazardous voltage. Such
openings include, but are not limited to,
excessively wide cabinet ventilation slots, and an
improperly fitted and/or incorrectly secured
cabinet back cover.
(3) Leakage Current Hot Check-With the instrument
completely reassembled, plug the AC line cord
directly into a 120V AC outlet. (Do not use a
isolation transformer during this test.) Use a
leakage current tester or a metering system that
complies with American National Standards
institute (ANSI) C101.1 Leakage Current for
Appliances and Underwriters Laboratories (UL)
1270 (40.7). With the instruments AC switch first
in the ON position and then in the OFF position,
measure from a known earth ground (metal water
pipe, conduit, etc.) to all exposed metal parts of the
instrument (antennas, handle brackets, metal
cabinets, screwheads, 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 0.5mA.
Reverse the instrument power cord plug in the
outlet and repeat the test. See Fig. 1-1.Any measurements not within the limits specified
herein indicate a potential shock hazard that must
be eliminated before returning the instrument to
the customer.
Fig. 1-1 AC Leakage Test
(4) Insulation Resistance Test Cold Check-(1) Unplug
the power supply cord and connect a jumper wire
between the two prongs of the plug. (2) Turn on
the power switch of the instrument. (3) Measure
the resistance with an ohmmeter between the
jumpered AC plug and all exposed metallic
cabinet parts on the instrument, such as
screwheads, antenna, control shafts, handle
brackets, etc. When an exposed metallic part has a
return path to the chassis, the reading should be
between 1 and 5.2 megohm. When there is no
return path to the chassis, the reading must be
infinite. If the reading is not within the limits
specified, there is the possibility of a shock hazard,
and the instrument must be re-pared and
rechecked before it is returned to the customer. See
Fig. 1-2.
Fig. 1-2 Insulation Resistance Test
DEVICE
UNDER
TEST(READING SHOULD
NOT BE ABOVE
0.5mA) LEAKAGE
CURRENT
TESTER
EARTH
GROUND TEST ALL
EXPOSED METER
SURFACES ALSO TEST WITH
PLUG REVERSED
(USING AC ADAPTER
PLUG AS REQUIRED)
2-WIRE CORD
Antenna
Terminal
Exposed
Melal Part
ohm
ohmmeter
Page 2
Precautions
1-2
2) Read and comply with all caution and safety re-
lated notes non or inside the cabinet, or on the
chassis.
3) Design Alteration Warning-Do not alter of add to
the mechanical or electrical design of this
instrument. Design alterations and additions,
including but not limited to, circuit modifications
and the addition of items such as auxiliary audio
output connections, might alter the safety
characteristics of this instrument and create a
hazard to the user. Any design alterations or
additions will make you, the service, responsible
for personal injury or property damage resulting
therefrom.
4) Observe original lead dress. Take extra care to
assure correct lead dress in the following areas:
(1) near sharp edges, (2) near thermally hot parts
(be sure that leads and components do not touch
thermally hot parts), (3) the AC supply, (4) high
voltage, and (5) antenna wiring. Always inspect in
all areas for pinched, out-of-place, or frayed wiring,
Do not change spacing between a component and
the printed-circuit board. Check the AC power cord
for damage.5) Components, parts, and/or wiring that appear to
have overheated or that are otherwise damaged
should be replaced with components, parts and/ 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.
6) Product Safety Notice-Some electrical and
mechanical parts have special safety-related
characteristics 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 by shading, an ( )or a ( )on
schematics and parts lists. Use of a substitute
replacement that does not have the same safety
characteristics as the recommended replacement
part might created shock, fire and/or other
hazards. Product safety is under review
continuously and new instructions are issued
whenever appropriate.