SERVICING PRECAUTIONS
CAUTION: Before servicing receivers covered by this serviceunit under test.
manual and its supplements and addenda, read and follow the2. After removing an electrical assembly equipped with ES
SAFETY PRECAUTIONS on page 3 of this publication.devices, place the assembly on a conductive surface such as
NOTE: If unforeseen circumstances create conflict between thealuminum foil, to prevent electrostatic charge buildup or
following servicing precautions and any of the safety precautions onexposure of the assembly.
page 3 of this publication, always follow the safety precautions.3. Use only a grounded-tip soldering iron to solder or unsolder ES
Remember: Safety First.devices.
4. Use only an anti-static type solder removal device. Some solder
General Servicing Precautionsremoval devices not classified as "anti-static" can generate
1. Always unplug the receiver AC power cord from the AC powerelectrical charges sufficient to damage ES devices.
source before;5. Do not use freon-propelled chemicals. These can generate
a. Removing or reinstalling any component, circuit boardelectrical charges sufficient to damage ES devices.
module or any other receiver assembly.6. Do not remove a replacement ES device from its protective
b. Disconnecting or reconnecting any receiver electrical plug orpackage until immediately before you are ready to install it.
other electrical connection.(Most replacement ES devices are packaged with leads
c. Connecting a test substitute in parallel with an electrolyticelectrically shorted together by conductive foam, aluminum foil
capacitor in the receiver.or comparable conductive material).
CAUTION: A wrong part substitution or incorrect polarity7. Immediately before removing the protective material from the
installation of electrolytic capacitors may result in anleads of a replacement ES device, touch the protective material
explosion hazard.to the chassis or circuit assembly into which the device will be
installed.
2. Test high voltage only by measuring it with an appropriate highCAUTION: Be sure no power is applied to the chassis or circuit,
voltage meter or other voltage measuring device (DVM,and observe all other safety precautions.
FETVOM, etc) equipped with a suitable high voltage probe.8. Minimize bodily motions when handling unpackaged
Do not test high voltage by "drawing an arc".replacement ES devices. (Otherwise harmless motion such as
3. Do not spray chemicals on or near this receiver or any of itsthe brushing together of your clothes fabric or the lifting of your
assemblies.foot from a carpeted floor can generate static electricity
4. Unless specified otherwise in this service manual, cleansufficient to damage an ES device.)
electrical contacts only by applying the following mixture to the
contacts with a pipe cleaner, cotton-tipped stick or comparableGeneral Soldering Guidelines
non-abrasive applicator; 10% (by volume) Acetone and 90% (by1. Use a grounded-tip, low-wattage soldering iron and appropriate
volume) isopropyl alcohol (90%-99% strength)tip size and shape that will maintain tip temperature within the
CAUTION: This is a flammable mixture.range or 500!LF to 600!LF.
Unless specified otherwise in this service manual, lubrication of2. Use an appropriate gauge of RMA resin-core solder composed
contacts in not required.of 60 parts tin/40 parts lead.
5. Do not defeat any plug/socket B+ voltage interlocks with which3. Keep the soldering iron tip clean and well tinned.
receivers covered by this service manual might be equipped.4. Thoroughly clean the surfaces to be soldered. Use a mall wire-
6. Do not apply AC power to this instrument and/or any of itsbristle (0.5 inch, or 1.25cm) brush with a metal handle.
electrical assemblies unless all solid-state device heat sinks areDo not use freon-propelled spray-on cleaners.
correctly installed.5. Use the following unsoldering technique
7. Always connect the test receiver ground lead to the receivera. Allow the soldering iron tip to reach normal temperature.
chassis ground before connecting the test receiver positive(500!LF to 600!LF)
lead.b. Heat the component lead until the solder melts.
Always remove the test receiver ground lead last.c. Quickly draw the melted solder with an anti-static, suction-
8. Use with this receiver only the test fixtures specified in thistype solder removal device or with solder braid.
service manual.CAUTION: Work quickly to avoid overheating the
CAUTION: Do not connect the test fixture ground strap to anycircuitboard printed foil.
heat sink in this receiver.6. Use the following soldering technique.
a. Allow the soldering iron tip to reach a normal temperature
Electrostatically Sensitive (ES) Devices(500!LF to 600!LF)
Some semiconductor (solid-state) devices can be damaged easilyb. First, hold the soldering iron tip and solder the strand against
by static electricity. Such components commonly are calledthe component lead until the solder melts.
Electrostatically Sensitive (ES) Devices. Examples of typical ESc. Quickly move the soldering iron tip to the junction of the
devices are integrated circuits and some field-effect transistors andcomponent lead and the printed circuit foil, and hold it there
semiconductor "chip" components. The following techniquesonly until the solder flows onto and around both the
should be used to help reduce the incidence of componentcomponent lead and the foil.
damage caused by static by static electricity.CAUTION: Work quickly to avoid overheating the circuit
1. Immediately before handling any semiconductor component orboard printed foil.
semiconductor-equipped assembly, drain off any electrostaticd. Closely inspect the solder area and remove any excess or
charge on your body by touching a known earth ground.splashed solder with a small wire-bristle brush.
Alternatively, obtain and wear a commercially available
discharging wrist strap device, which should be removed to
prevent potential shock reasons prior to applying power to the
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ACEC
