NAD L 76 Service Manual - Servicing Precautions

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SERVICING PRECAUTIONS

CAUTION : Before servicing the A/V Receiver covered by this

service data and its supplements and addends, read and follow the

SAFETY PRECAUTIONS. NOTE

: if unforeseen circumstances

create conflict between the following servicing precautions and any

of the safety precautions in this publication, always follow the safety

precautions.

Remember Safety First:

General Servicing Precautions

1. Always unplug the A/V Receiver AC power cord from the AC

power source before:

(1) Removing or reinstalling any component, circuit board,

module, or any other assembly.

(2) Disconnecting or reconnecting any internal electrical plug or

other electrical connection.

(3) Connecting a test substitute in parallel with an electrolytic

capacitor.

Caution : A wrong part substitution or incorrect polarity installation

of electrolytic capacitors may result in an explosion hazard.

2. Do not spray chemicals on or near this A/V Receiver or any of its

assemblies.

3. Unless specified otherwise in this service data, clean electrical

contacts by applying an appropriate contact cleaning solution to

the contacts with a pipe cleaner, cottontipped swab, or

comparable soft applicator.

Unless specified otherwise in this service data, lubrication of

contacts is not required.

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

instruments covered by this service manual might be equipped.

5. Do not apply AC power to this A/V Receiver and/or any of its

electrical assemblies unless all solid-state device heat sinks are

correctly installed.

6. Always connect test instrument ground lead to the appropriate

ground before connecting the test instrument positive lead. Always

remove the test instrument ground lead last.

Insulation Checking Procedure

Disconnect the attachment plug from the AC outlet and turn the

power on. Connect an 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

(Note 1) should be more than 1M-ohm.

Note 1 : Accessible Conductive Parts including Metal panels, Input

terminals, Earphone jacks, etc.

Electrostatically Sensitive (ES) Devices

Some semiconductor (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

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 ES 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 ES

devices.

4. Use only an antistatic solder removal device. Some solder

removal devices not classified a “anti-static” can generate

electrical charges sufficient to damage ES devices.

5. Do not use freonpropelled chemicals. These can generate

electrical charge sufficient to damage ES devices.

6. Do not remove a replacement ES device from its protective

package until immediately before you are ready to install it. (Most

replacement ES devices are packaged with leads electrically

shorted together by conductive foam, aluminum foil, or

comparable conductive material).

7. lmmediately 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 handing unpackaged replacement

ES devices. (Normally 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.)