SERVICING PRECAUTIONS
CAUTION: Before servicing receivers covered by this servicetransistors and semicounductor "chip" components. The
manual and its supplements and addenda, read and follow thefollowing techniques should be used to help reduce the
SAFETY PRECAUTIONSon page 3 of this publication.incidence of component damage caused by static by static
NOTE: If unforeseen circumstances create conflict between theelectricity.
following servicing precautions and any of the safety1. Immediately before handling any semiconductor component
precautions on page 3 of this publication, always follow theor semiconductor-equipped assembly, drain off any
safety precautions. Remember: Safety First.electostatic charge on your body by touching a known earth
ground. Alternatively, obtain and wear a commercially
General Servicing Precautionsavailable discharging wrist strap device, which should be
1. Always unplug the receiver AC power cord from the ACremoved to prevent potential shock reasons prior to
power source before;applying power to the unit under test.
a. Removing or reinstalling any component, circuit board2. After removing an electrical assembly equipped with ES
module or any other receiver assembly.devices, place the assembly on a conductive surface such as
b. Disconnecting or reconnecting any receiver electrical plugaluminum foil, to prevent electrostatic charge buildup or
or other electrical connection.exposure of the assembly.
c. Connecting a test substitute in parallel with an electrolytic3. Use only a grounded-tip soldering iron to solder or unsolder
capacitor in the receiver.ES devices.
CAUTION: A wrong part substitution or incorrect4. Use only an anti-static type solder removal device. Some
polarity installation of electrolytic capacitors may resultsolder removal devices not classified as "anti-static" can
in an explosion hazard.generate electrical charges sufficent to demage ES devices.
d. Discharging the picture tube anode.5. Do not use freon-propelled chemicals. These can generate
2. Test high voltage only by measuring it with an appropriateelectrical charges sufficient to damage ES devices.
high voltage meter or other voltage measuring device (DVM,6. Do not remove a repalcement ES device from its protective
FETVOM, etc) equipped with a suitable high voltage probe.package until immediately before you are ready to install it.
Do not test high voltage by "drawing an arc".(Most replacement ES devices are packaged with leads
3. Discharge the picture tube anode only by (a) first connectingelectrically shorted together by conductive foam, aluminum
one end of an insulated clip lead to the degaussing or kinefoil or comparable conductive material).
aquadag grounding system shield at the point where the7. Immediately before removing the protective material from
picture tube socket ground lead is connected, and then (b)the ieads of a replacement ES device, touch the protective
touch the other end of the insulated clip lead to the picturematerial to the chassis or circuit assembly into which the
tube anode button, using an insulating handle to avoiddevice will be installed.
personal contact with high voltage.CAUTION:Be sure no power is applied to the chassis or
4. Do not spray chemicals on or near this receiver or any of itscircuit, and observe all other safety precautions.
assemblies.8. Minimize bodily motions when handling unpackaged
5. Unless specified otherwise in this service manual, cleanreplacement ES devices. (Otherwise harmless motion such
electrical contacts only by applying the following mixture toas the bruching together of your clothes fabric or the lifting
the contacts with a pipe cleaner, cotton-tipped stick orof your foot from a carpeted floor can generate static
comparable nonabrasive applicator; 10% (by volume)electricity sufficient to damage an ES device.)
Acetone and 90% (by volume) isopropyl alcohol (90%-99%
strength)General Soldering Guidelines
CAUTION: This is a flammable mixture.1. Use a grounded-tip, low-wattage soldering iron and
Unless specified otherwise in this service manual, lubricationappropriate tip size and shape that will maintan tip
of contacts in not required.temperature within the range or 500!LF to 600!LF.
6. Do not defeat any plug/socket B+ voltage interlocks with2. Use an appropriate gauge of RMA resin-core solder
which receivers covered by this service manual might becomposed of 60 parts tin/40 parts lead.
equipped.3. Keep the soldering iron tip clean and well tinned.
7. Do not apply AC power to this instrument and/or any of its4. Thorohly clean the surfaces to be soldered. Use a mall
electrical assemblies unless all solid-state device heat sinkswirebristle (0.5 inch, or 1.25cm) brush with a metal handle.
are correctly installed.Do not use freon-propelled spray-on cleaners.
8. Always connect the test receiver ground lead to the5. Use the following unsoldering technique
receiver chassis ground before connecting the test receivera. Allow the soldering iron tip to reach normal temperature.
positive lead.(500!LF to 600!LF)
Always remove the test receiver ground lead last.b. Heat the component lead until the solder melts.
9. Use with this receiver only the test fixtures specified in thisc. Quickly draw the melted solder with an anti-static,
service manual.suction-type solder removal device or with solder braid.
CAUTION: Do not connect the test fixture ground strap toCAUTION: Work quickly to avoid overheating the
any heatsink in this receiver.circuiboard printed foil.
6. Use the following soldering technique.
Electrostatically Sensitive (ES) Devicesa. Allow the soldering iron tip to reach a normal
Some semiconductor (solid state) devices can be damagedtemperature (500!LF to 600!LF)
easily by static electricity. Such components commonly areb. First, hold the soldering iron tip and solder the strand
called Electrostatically Sensitive (ES) Devices.Examples ofagainst the component lead until the solder melts.
typical ES devices are integrated circuits and some fieldeffect
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ACEC
