Service manual

SERVICING
CM153 - 923-03443R1 4 ZLD20A1 - SERVICING
SERVICING PRECAUTIONS
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
precautions 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 performing the following.
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.
2. Test high voltage only by measuring it with an ap-
propriate high voltage meter or other voltage-mea-
suring device (DVM, FETVOM, etc) equipped with a
suitable high voltage probe. Do not test high volt-
age by “drawing an arc”.
3. Discharge the picture tube anode only by (a) first
connecting one end of an insulated clip lead to the
degaussing or kine aquadag grounding system shield
at the point where 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 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 follow-
ing mixture to the contacts with a pipe cleaner, cot-
ton-tipped stick or comparable nonabrasive applica-
tor; 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 con-
tacts in not required.
6. Do not defeat any plug/socket B+ voltage interlocks
with which receivers covered by this service manual
might be equipped.
7. Do not apply AC power to this instrument and/or any
of its electrical assemblies unless all solid-state de-
vice heat sinks are correctly installed.
8. Always connect the test receiver ground lead to the
receiver 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 heatsink in this receiver.
ELECTROSTATIC SENSITIVE (ES) DEVICES
Some semiconductor (solid state) devices can be
damaged easily by static electricity. Such components
commonly are called Electrostatic Sensitive Devices.
Examples of typical ES devices are integrated circuits
and some field effect transistors and semiconductor “chip”
components. The following techniques should be used
to help reduce the incidence of component damage
caused by static electricity.
1. Immediately before handling any semiconductor com-
ponent or semiconductor-equipped assembly, drain
off any electrostatic charge on your body by touch-
ing a known earth ground. Alternatively, obtain and
wear a commercially available discharging wrist strap
device, which should be removed to prevent poten-
tial shock reasons prior to applying power to the
unit under test.
2. After removing an electrical assembly equipped with
ES devices, place the assembly on a conductive sur-
face 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 gen-
erate electrical charges sufficient to damage ES de-
vices.
6. Do not remove a replacement ES device from its pro-
tective package until immediately before you are ready
to install it. (Most replacement ES devices are pack-
aged with leads electrically shorted together by con-
ductive foam, aluminum foil or comparable conduc-
tive material).
7. Immediately before removing the protective material
from the leads of a replacement ES device, touch the
protective 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
replacement ES devices. (Otherwise 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.)