Servicing Precautions - Hitachi 36UX59B Service Manual

MSLXU
SERVICING PRECAUTIONS
CAUTION: Before servicing instruments covered by this service
data and its supplements and addenda, read and follow the SAFE-
TY PRECAUTIONS on page 3 of this publication.
NOTE: If unforseen circumstances create conflict between the fol-
lowing servicing precautions and any of the safety precautions on
page 3 of this publication, always follow the safety precautions.
Remember: Safety First.
General Servicing Guidelines
1. Always unplug the instrument AC power cord from the AC
power source before:
a. Removing or reinstalling any component, circuit board,
module, or any other instrument assembly.
b. Disconnecting or reconnecting any instrument electrical
plug or other electrical connection.
c. Connecting a test substitute in parallel with an electrolyt-
ic capacitor in the instrument.
CAUTION: A wrong part substitution or incorrect
polarity installation of electrolytic
capacitors may result in an
explosion hazard.
d. Discharging the picture tube anode.
2. Test high voltage only by measuring it wih an appropriate high
voltage meter or other voltage measuring device (DVM,
FETVOM, etc.) equipped with a suitable high voltage probe.
Do not test high voltage by "drawing an arc."
3. Discharge the picture tube's anode by (a) first connecting one
end of an insulated clip lead to the degaussing or kine
aquadag grounding system shield at the point where the pic-
ture tube socket ground lead is connected, and then (b) touch
the other end of the insulated clip lead to the picture tube high
voltage output, using an insulated handle to avoid personal
contact with high voltage.
8. Always connect the test instrument ground lead to the appro-
priate instrument chassis ground before connecting the test
instrument positive lead. Always remove the test instrument
ground lead last.
9. Use with this instrument only the test fixtures specified in this
service data.
CAUTION: Do not connect the test fixture ground strap to
any heatsink in this instrument.
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 dam-
age caused by static electricity.
1. Immediately before handling any semiconductor component
or semiconductor-equipped assembly, drain off any electro-
static charge on your body by touching a known earth ground.
Alternatively, obtain and wear a commercially available dis-
charging 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 surface such as
aluminum foil, to prevent electrostatic charge build-up or
exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or desolder
ES devices.
4. Use only an anti-static type solder removal device. Some sol-
der removal devices not classified as "anti-static" can gener-
ate electrical charges sufficient to damage ES device.
4. Do not spray chemicals on or near this instrument or any of its 5. Do not use freon-propelled chemicals. These can generate
assemblies. electrical charges sufficient to damage ES devices.
5. Unless specified otherwise in these service data, clean elec-
trical contacts by applying the following mixture to the contacts
with a pipe cleaner, cotton-tipped stick or comparable
nonabrasive applicator: 10% (by volume) Acetone and 90%
(by volume) ispropyle alchohol (90%-99% strength).
CAUTION: This is a flammable mixture. Unless specified
otherwise in these service data, lubrication of
contacts is not required.
6. Do not defeat any plug/socket B+ voltage interlocks with
which instruments covered by this service data might be
equipped.
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 elec-
trically 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 mate-
rial 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 handling unpackaged
replace-
ment ES devices. (Otherwise harmless motion such as the
7.
DO
not apply AC power to this instrument and/or any of its brushing together of your clothes fabric or the lifting of Your
electrical assemblies unless all solid-state device heat-sinks foot from a carpeted floor can generate static electricity
Suffi-
are correctly installed. cient to damage an ES device.)
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