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CAUTION: Before servicing receivers covered by this service
manual and its su lements and addenda, read and follow the
SAFETY PRECAUTIONS on age 3 of this ublication.
NOTE: If unforeseen circumstances create conflict between the
following servicing recautions and any of the safety
recautions on age 3 of this ublication, always follow the
safety recautions. Remember: Safety First.
General Servicing Preca tions
1. Always un lug the receiver AC ower cord from the AC
ower source before;
a. Removing or reinstalling any com onent, circuit board
module or any other receiver assembly.
b. Disconnecting or reconnecting any receiver electrical lug
or other electrical connection.
c.
Connecting a test substitute in arallel with an electrolytic
ca acitor in the receiver.
CAUTION: A wrong art substitution or incorrect
olarity installation of electrolytic ca acitors may result
in an ex losion hazard.
d. Discharging the icture tube anode.
2. Test high voltage only by measuring it with an a ro riate
high voltage meter or other voltage measuring device (DVM,
FETVOM, etc) equi ed with a suitable high voltage robe.
Do not test high voltage by "drawing an arc".
3. Discharge the icture tube anode only by (a) first connecting
one end of an insulated cli lead to the degaussing or kine
aquadag grounding system shield at the oint where the
icture tube socket ground lead is connected, and then (b)
touch the other end of the insulated cli lead to the icture
tube anode button, using an insulating handle to avoid
ersonal contact with high voltage.
4. Do not s ray chemicals on or near this receiver or any of its
assemblies.
5. Unless s ecified otherwise in this service manual, clean
electrical contacts only by a lying the following mixture to
the contacts with a i e cleaner, cotton-ti ed stick or
com arable nonabrasive a licator; 10% (by volume)
Acetone and 90% (by volume) iso ro yl alcohol (90%-99%
strength)
CAUTION: This is a flammable mixture.
Unless s ecified otherwise in this service manual, lubrication
of contacts in not required.
6. Do not defeat any lug/socket B+ voltage interlocks with
which receivers covered by this service manual might be
equi ed.
7. Do not a ly AC ower to this instrument and/or any of its
electrical assemblies unless all solid-state device heat sinks
are correctly installed.
8. Always connect the test receiver ground lead to the
receiver chassis ground before connecting the test receiver
ositive lead.
Always 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 stra to
any heatsink in this receiver.
Electrostatically Sensitive (ES) Devices
Some semiconductor (solid state) devices can be damaged
easily by static electricity. Such com onents commonly are
called Electrostatically Sensitive (ES) Devices. Exam les of
ty ical ES devices are integrated circuits and some fieldeffect
transistors and semicounductor "chi " com onents. The
following techniques should be used to hel reduce the
incidence of com onent damage caused by static by static
electricity.
1. Immediately before handling any semiconductor com onent
or semiconductor-equi ed assembly, drain off any
electostatic charge on your body by touching a known earth
ground. Alternatively, obtain and wear a commercially
available discharging wrist stra device, which should be
removed to revent otential shock reasons rior to
a lying ower to the unit under test.
2. After removing an electrical assembly equi ed with ES
devices, lace the assembly on a conductive surface such as
aluminum foil, to revent electrostatic charge buildu or
ex osure of the assembly.
3. Use only a grounded-ti soldering iron to solder or unsolder
ES devices.
4. Use only an anti-static ty e solder removal device. Some
solder removal devices not classified as "anti-static" can
generate electrical charges sufficent to demage ES devices.
5. Do not use freon- ro elled chemicals. These can generate
electrical charges sufficient to damage ES devices.
6. Do not remove a re alcement ES device from its rotective
ackage until immediately before you are ready to install it.
(Most re lacement ES devices are ackaged with leads
electrically shorted together by conductive foam, aluminum
foil or com arable conductive material).
7. Immediately before removing the rotective material from
the ieads of a re lacement ES device, touch the rotective
material to the chassis or circuit assembly into which the
device will be installed.
CAUTION:Be sure no ower is a lied to the chassis or
circuit, and observe all other safety recautions.
8. Minimize bodily motions when handling un ackaged
re lacement ES devices. (Otherwise harmless motion such
as the bruching together of your clothes fabric or the lifting
of your foot from a car eted floor can generate static
electricity sufficient to damage an ES device.)
General Soldering G idelines
1. Use a grounded-ti , low-wattage soldering iron and
a ro riate ti size and sha e that will maintan ti
tem erature within the range or 500°F to 600°F.
2. Use an a ro riate gauge of RMA resin-core solder
com osed of 60 arts tin/40 arts lead.
3. Kee the soldering iron ti clean and well tinned.
4. Thorohly clean the surfaces to be soldered. Use a mall
wirebristle (0.5 inch, or 1.25cm) brush with a metal handle.
Do not use freon- ro elled s ray-on cleaners.
5. Use the following unsoldering technique
a. Allow the soldering iron ti to reach normal tem erature.
(500°F to 600°F)
b. Heat the com onent lead until the solder melts.
c. Quickly draw the melted solder with an anti-static,
suction-ty e solder removal device or with solder braid.
CAUTION: Work quickly to avoid overheating the
circuiboard rinted foil.
6. Use the following soldering technique.
a. Allow the soldering iron ti to reach a normal
tem erature (500°F to 600°F)
b. First, hold the soldering iron ti and solder the strand
against the com onent lead until the solder melts.
SERVICING PRECAUTIONS
