1 Precautions
1-2 Servicing Precautions
WARNING:An electrolytic capacitor installed with the wrong polarity might explode.
Caution:Before servicing units covered by this service manual, read and follow the Safety Precautions
section of this manual.
Note:If unforeseen circumstances create conflict between the following servicing precautions and any of the safety
precautions, always follow the safety precautions.
1-2-1 General Servicing
Precautions
1. Always unplug the unitOs AC power cord from the AC4. Check the insulation between the blades of the AC plug
power source and disconnect the DC Power Jack beforeand accessible conductive parts (examples: metal panels,
attempting to:input terminals and earphone jacks).
(a) remove or reinstall any component or assembly, (b)5. Insulation Checking Procedure: Disconnect the power
disconnect PCB plugs or connectors, (c) connect a testcord from the AC source and turn the power switch ON.
component in parallel with an electrolytic capacitor.Connect an insulation resistance meter (500 V) to the
2. Some components are raised above the printed circuitblades of the AC plug.
board for safety. An insulation tube or tape is sometimesThe insulation resistance between each blade of the AC
used. The internal wiring is sometimes clamped toplug and accessible conductive parts (see above) should
prevent contact with thermally hot components. Reinstallbe greater than 1 megohm.
all such elements to their original position.
6. Always connect a test instrumentOs ground lead to the
3. After servicing, always check that the screws,instrument chassis ground before connecting the positive
components and wiring have been correctly reinstalled.lead; always remove the instrumentOs ground lead last.
Make sure that the area around the serviced part has not
been damaged.
1-3 Electrostatically Sensitive Devices (ESD) Precautions
Some semiconductor (solid state) devices can be easily damaged by static electricity. Such components are commonly called
Electrostatically Sensitive Devices (ESD). Examples of typical ESD are integrated circuits and some field-effect transistors. The
following techniques will reduce the incidence of component damage caused by static electricity.
1. Immediately before handling any semiconductor6. Do not remove a replacement ESD from its protective
components or assemblies, drain the electrostatic chargepackage until you are ready to install it. Most
from your body by touching a known earth ground.replacement ESDs are packaged with leads that are
Alternatively, wear a discharging wrist-strap device. Toelectrically shorted together by conductive foam,
avoid a shock hazard, be sure to remove the wrist strapaluminum foil or other conductive materials.
before applying power to the monitor.7. Immediately before removing the protective material
2. After removing an ESD-equipped assembly, place it on afrom the leads of a replacement ESD, touch the
conductive surface such as aluminum foil to preventprotective material to the chassis or circuit assembly into
accumulation of an electrostatic charge.which the device will be installed.
3. Do not use freon-propelled chemicals. These canCaution: Be sure no power is applied to the
generate electrical charges sufficient to damage ESDs.chassis or circuit and observe all
4. Use only a grounded-tip soldering iron to solder orother safety precautions.
desolder ESDs.
5. Use only an anti-static solder removal device. Some8. Minimize body motions when handling unpackaged
solder removal devices not classified as Oanti-static� canreplacement ESDs. Motions such as brushing clothes
together, or lifting your foot from a carpeted floor can
generate electrical charges sufficient to damage ESDs.generate enough static electricity to damage an ESD.
1-2MH17WS |
ACEC
