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2 SERVICING PRECAUTIONS
CAUTION:
Before servicing units covered by this service manual
and its supplements, read and follow the Safety Precautions section
of this manual.
Note:
If unforseen circumstances create conflict between the
following servicing precautions and any of the safety precautions,
always follow the safety precautions. Remember: Safety First.
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 installed.
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 identified 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 installed 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.
2-2 Insulation Checking Procedure
Disconnect the attachment plug from the AC outlet and turn the
power ON. Connect the insulation resistance 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.
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