CAUTION: Before servicing receivers covered by this
service manual and its supplements and addenda, read
and follow the SAFETY PRECAUTIONS on page
3 of this
publication.
NOTE: If unforeseen circumstances create conflict
between the following servicing precautions and any of the
safety p
recautions on page 3 of this publication, always
follow the safety precautions. Remember: Safety First.
General Servicing Precautions
1. Always unplug the receiver AC power cord from the AC
power 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 with an
electrolytic capacitor in the receiver.
CAUTION:
A wrong 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 with an
appropri
ate high voltage meter or other voltage
measuring device (DVM, FETVOM, etc) equipped
with
a suitable high voltage probe.
Do not test high voltage by "drawing an arc".
3. Discharge the picture tube anode only by (a) first
connecti
ng one end of an insulated clip lead to the
degaussi
ng or kine aquadag grounding system shield
at the point where the picture tube
socket ground lead
is connec
ted, and then (b) touch the other end of the
insulate
d clip lead to the picture tube anode button,
using an
insulating handle to avoid personal contact
with high voltage.
4. Do not spray chemicals on
or near this receiver or any
of its assemblies.
5. Unless specified otherwise in this service manual,
clean electrical contacts only by
applying the following
mixture
to the contacts with a pipe cleaner, cotton-
tipped s
tick or comparable non-abrasive applicator;
10% (by
volume) Acetone and 90% (by volume)
isopropyl alcohol (90%-99% strength)
CAUTION: This is a flammable mixture.
Unless
specified otherwise in this service manual,
lubrication of contacts in not required.
6. Do not
defeat any plug/socket B+ voltage interlocks
with whi
ch receivers covered by this service manual
might be equipped.
7. Do not apply AC power
to this instrument and/or any of
its elec
trical assemblies unless all solid-state device
heat sinks are correctly installed.
8. Always
connect the test receiver ground lead to the
receive
r chassis ground before connecting the test
receiver positive 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 strap
to any heat sink in this receiver.
Electrostatically Sensitive (ES) Devices
Some sem
iconductor (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
semicond
uctor "chip" components. The following
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
known ea
rth ground. Alternatively, obtain and wear a
commerci
ally available discharging wrist strap device,
which sh
ould be removed to prevent potential shock
reasons prior to applying power to the unit under test.
2. After
removing an electrical assembly equipped with
ES devic
es, 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 onl
y an anti-static type solder removal device.
Some sol
der 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
protecti
ve package until immediately before you are
ready to
install it. (Most replacement ES devices are
packaged
with leads electrically shorted together by
conducti
ve foam, aluminum foil or comparable
conductive material).
7. Immedi
ately before removing the protective material
from the leads of a replacement
ES device, touch the
protecti
ve material to the chassis or circuit assembly
into which the device will be installed.
CAUTION: Be sure no power is
applied to the chassis
or circuit, and observe all other safety precautions.
8. Minimize bodily motions when handling unpackaged
replacem
ent ES devices. (Otherwise harmless motion
such as the brushing together of
your clothes fabric or
the lift
ing of your foot from a carpeted floor can
generate
static electricity sufficient to damage an ES
device.)
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