SERVICING PRECAUTIONS
CAUTION: Before servicing instruments covered by this Do not apply AC power to this instrument and/or any of its
service data and its supplements and addenda, read and electrical assemblies unless all solid-state device heat-
follow the SAFETY PRECAUTIONS on page 3 of this sinks are correctly installed.
publication.
NOTE: If unforeseen circumstances create conflict between Always connect the test instrument ground lead to the
the following servicing precautions and any of the safety appropriate instrument chassis ground before connecting
precautions on page 3 of this publication, always follow the the test instrument positive lead. Always remove the test
safety precautions. Remember: Safety First. instrument ground lead last.
General Servicing Guidelines Use with this instrument only the test fixtures specified in
1. Always unplug the instrument AC power cord from the AC this service data.
power source before: CAUTION: Do not connect the test fixture ground strap
a. Removing or reinstalling any component, circuit to any heatsink in this instrument.
board, module, or any other instrument assembly.
Electrostatically Sensitive (ES) Devices
b. Disconnecting or reconnecting any instrument Some semiconductor (solid state) devices can be damaged
easily by static electricity. Such components commonly are
electrical plug or other electrical connection.
called Electrostatically Sensitive (ES) Devices. Examples of
c. Connecting a test substitute in parallel with an typical ES devices are integrated circuits and some fietd-
electrolytic capacitor in the instrument. effect transistors and semiconductor ?chip? components. The
CAUTION: A wrong part substitution or incorrect following techniques should be used to help reduce the
polarity installation of electrolytic incidence of component damage caused by static electricity.
capacitors may result in an explosion
hazard. 1. Immediately before handling any semiconductor
component or semiconductor-equipped assembly, drain
d. Discharging the picture tube anode. off any electrostatic charge on your body by touching a
known earth ground. Alternatively, obtain and wear a
2. Test high voltage only by measuring it with an appropriate commercially available discharging wrist strap device,
high voltage meter or other voltage measuring device which should be removed for potential shock reasons
(DVM, FETVOM, etc.) equipped with a suitable high prior to applying power to the unit under test.
voltage probe. Do not test high voltage by ?drawing an
arc.? The H.V. Distribution Box has an internal 400MR 2. After removing an electrical assembly equipped with ES
resistor (bleeder resistor) connected from the high devices, place the assembly on a conductive surface
voltage to ground. After power is removed from the such as aluminum foil, to prevent electrostatic charge
instrument the high voltage will discharge through the buildup or exposure of the assembly.
high voltage bleeder resistor. If the tubes have high
voltage after power is removed, then the bleeder resistor 3. Use only a grounded-tip soldering iron to solder or
is defective or the bleeder ground is disconnected. desolder ES devices.
3. Discharge the picture tube?s anode at any of the R, G, or 4. Use only can anti-static type solder removal device. Some
B outputs on the H.V. Distribution Box only by (a) first solder removal devices not classified as ?anti-static? can
connecting one end of an insulated clip lead to the generate electrical charges sufficient to damage ES
degaussing or kine aquadag grounding system shield at device.
the point where the picture tube socket ground lead is
conngcted, and then (b) touch the other end of the 5. Do not use freon-propelled chemicals. These can
insulated clip lead to the picture tube high voltage generate electrical charges sufficient to damage ES
distribution box R, G, or B output, using an insulated devices.
handle to avoid personal contact with high voltage.
6. Do not remove a replacement ES device from its
4. Do not spray chemicals on or near this instrument or any protective package until immediately before you are ready
of its assembfies. to install it. (Most replacement ES devices are packaged
with leads electrically shorted together by conductive
5. Unless specified otherwise in these service data, clean foam, aluminum foil or comparable conductive material.)
electrical contracts by applying the following mixture to
the contacts with a pipe cleaner, cotton-tipped stick or 7. Immediately before removing the protective material from
comparable nonabrasive applicator: 10% (by votume) the leads of a replacement ES device, touch the
Acetone and 90% (by volume) isopropyl alcohol (90%- protective material to the chassis or circuit assembly into
99% strength). which the device will be installed.
CAUTION: This is a flammable mixture. Unless CAUTION: Be sure no power is applied to the chassis or
specified otherwise in these service data, circuit, and observe all other safety
lubrication of contacts is not required. precautions.
6. Do not defeat any plug/socket B+ voltage interlocks with 8. Minimize bodily motions when handling unpackaged
which instruments covered by this service data might be replacement ES devices. (Otherwise harmless motion
equipped. such as the brushing together of your clothes fabric OP the
tifting of your foot from a carpeted floor can generate
static electricity sufficient to damage an ES device.)
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ACEC
