Servicing Precautions - Zenith XBV243 Service Manual

SERVICING PRECAUTIONS

CAUTION: Before servicing the product 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.
GENERAL SERVICING PRECAUTIONS
1. Always unplug the product 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 elec-
trical plug or other electrical connection.
(3) Connecting a test substitute in parallel with an
electrolytic capacitor.
CAUTION: A wrong part substitution or incorrect polarity
installation of electrolytic capacitors may result in
an explosion hazard.
2. Do not spray chemicals on or near this product or
any of its assemblies.
3. Unless specified otherwise in this service data, clean
electrical contacts by applying an appropriate con-
tact cleaning solution to the contacts with a pipe
cleaner, cotton-tipped swab, or comparable soft ap-
plicator. 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 product and/or any of
its electrical assemblies unless all solid-state device
heat sinks are correctly installed.
6. Always connect the test instrument ground lead to
the appropriate ground before connecting the test
instrument positive lead. Always remove the test in-
strument 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 resistance between each blade of the
attachment plug and accessible conductive parts should
be more than 1Mohm. Accessible conductive parts
include metal panels, input terminals, earphone jacks,
etc.
VR168 - 923-03485
All manuals and user guides at all-guides.com
SUMMARY
1-3
ELECTROSTATICALLY SENSITIVE (ES) DEVICES
Some semiconductor (solid state) devices can be
damaged easily by static electricity. Such components
commonly are called Electrostatically 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 handling any semiconductor com-
ponent or semiconductor-equipped assembly, drain
off any electrostatic charge on your body by touch-
ing a known earth ground. Alternatively, obtain and
wear a commercially available discharging wrist strap
device, which should be removed for potential shock
reasons 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 sur-
face 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 anti-static solder removal device. Some
solder removal devices not classified as "anti-static"
can generate electrical charges sufficient to damage
ES devices.
5. Do not use freon-propelled chemicals. These can gen-
erate an electrical charge sufficient to damage ES
devices.
6. Do not remove a replacement ES device from its pro-
tective 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 con-
ductive material).
7. Immediately before removing the protective mate-
rial from the leads of a replacement ES device, touch
the protective material to the chassis or circuit as-
sembly 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 handling unpackaged
replacement ES devices. (Normal 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.)
D35E COMBO - SUMMARY