Hitachi DVC-605U, Service Manual

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Precautions
1-3
1-2 Servicing Precautions
CAUTION : Before servicing Instruments covered
by this service manual and its supplements, read and
follow the Safety Precautions section of this manual.
Note : If unforseen circument create conflict between
the following servicing precautions and any of the
safety precautions, always follow the safety
precautions. Remember: Safety First.
1-2-1 General Servicing Precautions
(1) a. Always unplug the instrument's AC power cord
from the AC power source before (1) re-moving
or reinstalling any component, circuit board,
module or any other instrument assembly, (2)
disconnecting any instrument electrical plug or
other electrical connection, (3) connecting a test
substitute in parallel with an electrolytic
capacitor in the instrument.
b. Do not defeat any plug/socket B+ voltage
interlocks with which instruments covered by
this service manual might be equipped.
c. Do not apply AC power to this instrument and
/or any of its electrical assemblies unless all
solid-state device heat sinks are correctly in-
stalled.
d. Always connect a test instrument's ground lead
to the instrument chassis ground before
connecting the test instrument positive lead.
Always remove the test instrument ground lead
last.
Note : Refer to the Safety Precautions section ground
lead last.
(2) The service precautions are indicated or printed on
the cabinet, chassis or components. When
servicing, follow the printed or indicated service
precautions and service materials.
(3) The components used in the unit have a specified
flame resistance and dielectric strength.
When replacing components, use components
which have the same ratings. Components i-
entified by shading, by( ) or by ( ) in the circuit
diagram are important for safety or for the
characteristics of the unit. Always replace them
with the exact replacement components.
(4) An insulation tube or tape is sometimes used and
some components are raised above the printed
wiring board for safety. The internal wiring is
sometimes clamped to prevent contact with
heating components. Install such elements as they
were.
(5) After servicing, always check that the removed
screws, components, and wiring have been in-
stalled correctly and that the portion around the
serviced part has not been damaged and so on.
Further, check the insulation between the blades of
the attachment plug and accessible conductive
parts.
1-2-2 Insulation Checking Procedure
Disconnect the attachment plug from the AC outlet
and turn the power ON. Connect the insulation resi-
stance meter (500V) to the blades of the attachment
plug. The insulation resistance between each blade of
the attachment plug and accessible conductive
parts(see note) should be more than 1 Megohm.
Note : Accessible conductive parts include metal
panels, input terminals, earphone jacks, etc.