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1) Before returning an instrument to the customer, always make a

safety check of the entire instrument, including, but not limited
to, the following items:

(1) Be sure that no built-in protective devices are defective or have

been defeated during servicing.
(1)Protective shields are provided to protect both the technician
and the customer. Correctly replace all missing protective shields,
including any removed for servicing convenience.
(2)When reinstalling the chassis and/or other assembly in the
cabinet, be sure to put back in place all protective devices,
including, but not limited to, nonmetallic control knobs, insulating
fish papers, adjustment and compartment covers/shields, and
isolation resistor/capacitor networks. Do not operate this
instrument or permit it to be operated without all protective devices
correctly installed and functioning.

(2) Be sure that there are no cabinet openings through which adults

or children might be able to insert their fingers and contact a
hazardous voltage. Such openings include, but are not limited to,
excessively wide cabinet ventilation slots, and an improperly fitted
and/or incorrectly secured cabinet back cover.

(3) Leakage Current Hot Check-With the instrument completely

reassembled, plug the AC line cord directly into a 120V AC outlet.
(Do not use an isolation transformer during this test.) Use a leakage
current tester or a metering system that complies with American
National Standards institute (ANSI) C101.1 Leakage Current for
Appliances and Underwriters Laboratories (UL) 1270 (40.7). With
the instrument’s AC switch first in the ON position and then in the
OFF position, measure from a known earth ground (metal water
pipe, conduit, etc.) to all exposed metal parts of the instrument
(antennas, handle brackets, metal cabinets, screwheads, metallic
overlays, control shafts, etc.), especially any exposed metal parts
that offer an electrical return path to the chassis.
Any current measured must not exceed 0.5mA. Reverse the
instrument power cord plug in the outlet and repeat the test. See
Fig. 1.
Any measurements not within the limits specified herein indicate
a potential shock hazard that must be eliminated before returning
the instrument to the customer.

(4) Insulation Resistance Test Cold Check-(1) Unplug the power

supply cord and connect a jumper wire between the two prongs of
the plug. (2) Turn on the power switch of the instrument. (3)
Measure the resistance with an ohmmeter between the jumpered
AC plug and all exposed metallic cabinet parts on the instrument,
such as screwheads, antenna, control shafts, handle brackets, etc.
When an exposed metallic part has a return path to the chassis, the
reading should be between 1 and 5.2 megohm. When there is no
return path to the chassis, the reading must be infinite. If the reading
is not within the limits specified, there is the possibility of a shock
hazard, and the instrument must be repared and rechecked before
it is returned to the customer. See Fig. 2.

DEVICE

UNDER

TEST

(READING SHOULD

NOT BE ABOVE

0.5mA)

LEAKAGE

CURRENT

TESTER

EARTH

GROUND

TEST ALL

EXPOSED METER

SURFACES

ALSO TEST WITH
PLUG REVERSED

(USING AC ADAPTER
PLUG AS REQUIRED)

2-WIRE CORD

Fig. 1 AC Leakage Test

Fig. 2 Insulation Resistance Test

2) Read and comply with all caution and safety related notes on or

inside the cabinet, or on the chassis.

3) Design Alteration Warning-Do not alter or add to the mechanical

or electrical design of this instrument. Design alterations and
additions, including but not limited to, circuit modifications and
the addition of items such as auxiliary audio output connections,
might alter the safety characteristics of this instrument and create
a hazard to the user. Any design alterations or additions will make
you, the servicer, responsible for personal injury or property
damage resulting therefrom.

4) Observe original lead dress. Take extra care to assure correct lead

dress in the following areas:
(1) near sharp edges, (2) near thermally hot parts (be sure that
leads and components do not touch thermally hot parts), (3) the
AC supply, (4) high voltage, and (5) antenna wiring. Always inspect
in all areas for pinched, out-of-place, or frayed wiring, Do not
change spacing between a component and the printed-circuit board.
Check the AC power cord for damage.

5) Components, parts, and/or wiring that appear to have overheated

or that are otherwise damaged should be replaced with components,
parts and/ or wiring that meet original specifications.
Additionally, determine the cause of overheating and/or damage
and, if necessary, take corrective action to remove any potential
safety hazard.

Antenna
Terminal

Exposed
Metal Part

ohm

ohmmeter

— 6 —

6) Product Safety Notice-Some electrical and mechanical parts have

special safety-related characteristics which are often not evident
from visual inspection, nor can the protection they give necessarily
be obtained by replacing them with components rated for higher
voltage, wattage, etc. Parts that have special safety characteristics
are identified by shading, an (

) or a (

) on schematics and

parts lists. Use of a substitute replacement that does not have the
same safety characteristics as the recommended replacement part
might create shock, fire and/or other hazards. Product safety is
under review continuously and new instructions are issued
whenever appropriate.

— 7 —

  Before servicing units covered by this service manual

and its supplements, read and follow the Safety Precautions section of
this manual.

 If unforseen circumstances create conflict between the following

servicing precautions and any of the safety precautions, always follow
the safety precautions. Remember: Safety First.

(1) a. Always unplug the instrument’s AC power cord from the AC

power source before (1) re-moving or reinstalling any
component, circuit board, module or any other instrument
assembly, (2) disconnecting any instrument electrical plug or
other electrical connection, (3) connecting a test substitute in
parallel with an electrolytic capacitor in the instrument.

b. Do not defeat any plug/socket B+ voltage interlocks with which

instruments covered by this service manual might be equipped.

c. Do not apply AC power to this instrument and/or any of its

electrical assemblies unless all solid-state device heat sinks are
correctly installed.

d. Always connect a test instrument’s ground lead to the instrument

chassis ground before connecting the test instrument positive
lead. Always remove the test instrument ground lead last.

 Refer to the Safety Precautions section ground lead last.

(2) The service precautions are indicated or printed on the cabinet,

chassis or components. When servicing, follow the printed or
indicated service precautions and service materials.

(3) The components used in the unit have a specified flame resistance

and dielectric strength.
When replacing components, use components which have the same
ratings. Components identified by shading, by (

) or by (

) in

the circuit diagram are important for safety or for the characteristics
of the unit. Always replace them with the exact replacement
components.

(4) An insulation tube or tape is sometimes used and some components

are raised above the printed wiring board for safety. The internal
wiring is sometimes clamped to prevent contact with heating
components. Install such elements as they were.

(5) After servicing, always check that the removed screws,

components, and wiring have been installed correctly and that the
portion around the serviced part has not been damaged and so on.
Further, check the insulation between the blades of the attachment
plug and accessible conductive parts.

Disconnect the attachment plug from the AC outlet and turn the power
ON. Connect the insulation resistance meter (500V) to the blades of
the attachment plug. The insulation resistance between each blade of
the attachment plug and accessible conductive parts (see note) should
be more than 1 Megohm.

  Accessible conductive parts include metal panels, input

terminals, earphone jacks, etc.

— 8 —

Some semiconductor (solid state) devices can be damaged easily by
static electricity.
Such components commonly are called Electrostatically Sensitive
Devices (ESD). Examples of typical ESD 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 component or

semiconductor-equipped assembly, drain off any electrostatic
charge on your body by touching a known earth ground.
Alternatively, obtain and wear a commercially available
discharging wrist strap device, which should be removed for
potential shock reasons prior to applying power to the unit under
test.

(2) After removing an electrical assembly equipped with ESD 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 ESD

devices.

(4) Use only an anti-static solder removal devices. Some solder

removal devices not classified as “anti-static” can generate
electrical charges sufficient to damage ESD devices.

(5) Do not use freon-propelled chemicals. These can generate electrical

charges sufficient to damage ESD devices.

(6) Do not remove a replacement ESD device from its protective

package until immediately before your are ready to install it. (Most
replacement ESD devices are packaged with leads electrically
shorted together by conductive foam, aluminum foil or comparable
conductive materials).

(7) Immediately before removing the protective materials from the

leads of a replacement ESD device, touch the protective material
to the chassis or circuit assembly into which the device will be
installed.

 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

ESD 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 ESD device).