SERVICING PRECAUTIONS
CAUTION:Before servicing the Surround sound preamplifier
covered by this service data and its supplements and addends,
read and follow the SAFETY PRECAUTIONS. NOTE: if
unforeseen circumstances create conflict between the following
servicing precautions and any of the safety precautions in this
publication, always follow the safety precautions. Remember
Safety First:
General Servicing Precautions
1. Always unplug the Surround sound preamplifier AC
power cord from the AC power source before:
(1) Removing or reinstalling any component, circuit board,
module, or any other assembly.
(2) Disconnecting or reconnecting any internal electrical plug
or other electrical connection.
(3) Connecting a test substitute in parallel with an electrolytic
capacitor.
Caution: A wrong part substitute or incorrect polarity
installation of electrolytic capacitors may result in an
explosion hazard.
2. Do not spray chemicals on or near this Surround sound
preamplifier or any of its assemblies.
3. Unless specified otherwise in this service data, clean
electrical contacts by applying an appropriate contact
cleaning solution to the contacts with a pipe cleaner, cotton
tipped swab, or comparable soft applicator. Unless
specified otherwise in this service data, lubrication of
contacts is not required.
4. Do not defeat any plug/socket B+ voltage interlocks with
which instruments covered by this service manual might be
equipped.
5. Do not apply AC power to this Surround sound preamplifier
and/or any of its electrical assemblies unless all solid-state
device heat sinks are correctly installed.
6. Always connect test instrument ground lead to the
appropriate ground before connecting the test instrument
positive lead. Always remove the test instrument ground
lead last.
Insulation Checking Procedure
Disconnect the attachment plug from the AC outlet and turn the
power on. Connect an insulation resistance meter (500V) to the
blades of the attachment plug. The insulation resistances
between each blade of the attachment plug and accessible
conductive parts (Note 1) should be more than 1 M-ohm.
Note 1: Accessible Conductive Parts including Metal panels,
Input terminals, Earphone jacks, etc.
Electro statically Sensitive (ES) Devices
Some semiconductor (solid state) devices can be damaged
easily by static electricity. Such components commonly are
called Electro statically Sensitive (ES) Devices. Examples of
typical Es devices are integrated circuits and some field effect
transistors and semiconductor chip components. The
following techniques should be used to help reduce the
incidence of component damage caused by static electricity.
1. Immediately before handing any semiconductor component
or semiconductor-equipped assembly, drain off any
electrostatic charge on your body by touching a known
earth ground. Alternatively, obtain and wear a commercially
available discharging wrist strap device, which should be
removed for potential shock reason prior to applying power
to the unit under test.
2. After removing an electrical assembly equipped with ES
devices, place the assembly on a conductive surface such
as aluminum foil, to prevent electrostatic charge buildup or
exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder
ES devices.
4. Use only an antistatic solder removal device. Some solder
removal devices not classified a “anti-static” can generate
electrical charges sufficient to damage ES devices.
5. Do not use Freon propelled chemicals. These can generate
electrical charge sufficient to damage ES devices.
6. Do not remove a replacement ES device from its protective
package until immediately before you are ready to install it.
(Most replacement ES devices are packaged with leads
electrically shorted together by conductive foam, aluminum
foil, or comparable conductive material).
7. Immediately before removing the protective material from
the leads of a replacement ES device, touch the protective
material to the chassis or circuit assembly into which the
device will be installed.
Caution: Be sure no power is applied to the chassis or
circuit, and observe all other safety precautions.
8. Minimize bodily motions when handing unpackaged
replacement ES devices. (Normally harmless motion such
as the brushing together of your clothes fabric or the lifting
of your foot from a carpeted floor can generate static
electricity sufficient to damage an ES device.)
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