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CAUTION: Before servicing receivers covered by this service
manual and its supplements and addenda, read and follo the
SAFETY PRECAUTIONS on page 3 of this publication.
NOTE: If unforeseen circumstances create conflict bet een the
follo ing servicing precautions and any of the safety
precautions on page 3 of this publication, al ays follo the
safety precautions. Remember: Safety First.
General Servicing Precautions
1. Al ays unplug the receiver AC po er cord from the AC
po er source before;
a. Removing or reinstalling any component, circuit board
module or any other receiver assembly.
b. Disconnecting or reconnecting any receiver electrical plug
or other electrical connection.
c.
Connecting a test substitute in parallel ith an electrolytic
capacitor in the receiver.
CAUTION: A rong 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 ith an appropriate
high voltage meter or other voltage measuring device (DVM,
FETVOM, etc) equipped ith a suitable high voltage probe.
Do not test high voltage by "dra ing an arc".
3. Discharge the picture tube anode only by (a) first connecting
one end of an insulated clip lead to the degaussing or kind
aquadag grounding system shield at the point here the
picture tube socket ground lead is connected, and then (b)
touch the other end of the insulated clip lead to the picture
tube anode button, using an insulating handle to avoid
personal contact ith high voltage.
4. Do not spray chemicals on or near this receiver or any of its
assemblies.
5. Unless specified other ise in this service manual, clean
electrical contacts only by applying the follo ing mixture to
the contacts ith a pipe cleaner, cotton-tipped stick or
comparable nonabrasive applicator; 10% (by volume)
Acetone and 90% (by volume) isopropyl alcohol (90%-99%
strength)
CAUTION: This is a flammable mixture.
Unless specified other ise in this service manual, lubrication
of contacts in not required.
6. Do not defeat any plug/socket B+ voltage interlocks ith
hich receivers covered by this service manual might be
equipped.
7. Do not apply AC po er to this instrument and/or any of its
electrical assemblies unless all solid-state device heat sinks
are correctly installed.
8. Al ays connect the test receiver ground lead to the
receiver chassis ground before connecting the test receiver
positive lead.
Al ays remove the test receiver ground lead last.
9. Use with this receiver only the test fixtures specified in this
service manual.
CAUTION: Do not connect the test fixture ground strap to
any heatsink in this receiver.
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
follo ing techniques should be used to help reduce the
incidence of component damage caused by static by static
electricity.
1. Immediately before handling any semiconductor component
or semiconductor-equipped assembly, drain off any
electrostatic charge on your body by touching a kno n earth
ground. Alternatively, obtain and ear a commercially
available discharging rist strap device, hich should be
removed to prevent potential shock reasons prior to
applying po er to the unit under test.
2. After removing an electrical assembly equipped ith ES
devices, place the assembly on a conductive surface 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 type 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 generate
electrical charges sufficient to damage ES devices.
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 ith leads
electrically shorted together by conductive foam, aluminum
foil or comparable conductive material).
7. Immediately before removing the protective material from
the ieads of a replacement ES device, touch the protective
material to the chassis or circuit assembly into hich the
device ill be installed.
CAUTION:Be sure no po er is applied to the chassis or
circuit, and observe all other safety precautions.
8. Minimize bodily motions hen handling unpackaged
replacement ES devices. (Other ise 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.)
General Soldering Guidelines
1. Use a grounded-tip, lo - attage soldering iron and
appropriate tip size and shape that ill maintain tip
temperature ithin the range or 500°F to 600°F.
2. Use an appropriate gauge of RMA resin-core solder
composed of 60 parts tin/40 parts lead.
3. Keep the soldering iron tip clean and ell tinned.
4. Thorohly clean the surfaces to be soldered. Use a mall ire
bristle (0.5 inch, or 1.25cm) brush ith a metal handle.
Do not use freon-propelled spray-on cleaners.
5. Use the follo ing unsoldering technique
a. Allo the soldering iron tip to reach normal temperature.
(500°F to 600°F)
b. Heat the component lead until the solder melts.
c. Quickly dra the melted solder ith an anti-static,
suction-type solder removal device or ith solder braid.
CAUTION: Work quickly to avoid overheating the circuit
board printed foil.
6. Use the follo ing soldering technique.
a. Allo the soldering iron tip to reach a normal
temperature (500°F to 600°F)
b. First, hold the soldering iron tip and solder the strand
against the component lead until the solder melts.
SERVICING PRECAUTIONS