SERVICING PRECAUTIONS
CAUTION: Before servicing instruments covered by this service8. Always connect the test instrument ground lead to the appro-
data and its supplements and addenda, read and follow the SAFE-priate instrument chassis ground before connecting the test
TY PRECAUTIONS on page 3 of this publication.instrument positive lead. Always remove the test instrument
NOTE: If unforeseen circumstances create conflict between theground lead last.
following servicing precautions and any of the safety precautions
on page 3 of this publication, always follow the safety precautions. 9. Use with this instrument only the test fixtures specified in this
Remember: Safety First.service data.
CAUTION: Do not connect the test fixture ground strap to
General Servicing Guidelinesany heatsink in this instrument.
1. Always unplug the instrument AC power cord from the AC
power source before:Electrostatically Sensitive (ES) Devices
a. Removing or reinstalling any component, circuit board, Some semiconductor (solid state) devices can be damaged easily
module, or any other instrument assembly.by static electricity. Such components commonly are called
Electrostatically Sensitive (ES) Devices. Examples of typical ES
b. Disconnecting or reconnecting any instrument electrical devices are integrated circuits and some field-effect transistors
plug or other electrical connection.and semiconductor Ochip� components. The following techniques
should be used to help reduce the incidence of component dam-
c. Connecting a test substitute in parallel with an electrolyt-age caused by static electricity.
ic capacitor in the instrument.
CAUTION: A wrong part substitution or incorrect 1. Immediately before handling any semiconductor component
polarity installation of electrolytic or semiconductor-equipped assembly, drain off any electro-
capacitors may result in an static charge on your body by touching a known earth ground.
explosion hazard.Alternatively, obtain and wear a commercially available dis-
charging wrist strap device, which should be removed for
d. Discharging the picture tube anode.potential shock reasons prior to applying power to the unit
under test.
2. Test high voltage only by measuring it wih an appropriate high
voltage meter or other voltage measuring device (DVM,2. After removing an electrical assembly equipped with ES
FETVOM, etc.) equipped with a suitable high voltage probe.devices, place the assembly on a conductive surface such as
Do not test high voltage by Odrawing an arc.� aluminum foil, to prevent electrostatic charge build-up or
exposure of the assembly.
3. Discharge the picture tubeOs anode by (a) first connecting one
end of an insulated clip lead to the degaussing or kine3. Use only a grounded-tip soldering iron to solder or desolder
aquadag grounding system shield at the point where the pic-ES devices.
ture tube socket ground lead is connected, and then (b) touch
the other end of the insulated clip lead to the picture tube high4. Use only an anti-static type solder removal device. Some sol-
voltage output, using an insulated handle to avoid personalder removal devices not classified as Oanti-static� can gener-
contact with high voltage.ate electrical charges sufficient to damage ES device.
4. Do not spray chemicals on or near this instrument or any of its5. 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-6. Do not remove a replacement ES device from its protective
trical contacts by applying the following mixture to the contactspackage until immediately before you are ready to install it.
with a pipe cleaner, cotton-tipped stick or comparable(Most replacement ES devices are packaged with leads elec-
nonabrasive applicator: 10% (by volume) Acetone and 90%trically shorted together by conductive foam, aluminum foil or
(by volume) ispropyl alcohol (90%-99% strength).comparable conductive material.)
CAUTION: This is a flammable mixture. Unless specified
otherwise in these service data, lubrication of 7. Immediately before removing the protective material from the
contacts is not required.leads of a replacement ES device, touch the protective mate-
rial to the chassis or circuit assembly into which the device will
6. Do not defeat any plug/socket B+ voltage interlocks whichbe installed.
instruments covered by this service data might be equipped.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-
7. Do not apply AC power to this instrument and/or any of itsment ES devices. (Otherwise harmless motion such as the
electrical assemblies unless all solid-state device heat-sinksbrushing together of your clothes fabric or the lifting of your
are correctly installed.foot from a carpeted floor can generate static electricity suffi-
cient to damage an ES device.)
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