Servicing Precaution; Precaution For Electrostatically Sensitive Devices(Esds) - Samsung SRP-275 Service Manual

1-2 Servicing Precaution

WARNING 1 : First read the "Safety Precautions" section of this manual. If some unforeseen circumstance
creates a conflict between the servicing and safety precautions, always follow the safety
precautions.
WARNING 2 : An electrolytic capacitor installed with the wrong polarity might explode.
1. Always unplug the unit's AC power cord from the AC power source or the Power Switch off before
attempting to :
(a) Remove or reinstall any component or assembly,
(b) Disconnect an electrical plug or connector,
(c) Connect a test component in parallel with an electrolytic capacitor.
2. Some components are raised above the printed circuit board for safety. An insulation tube or tape is
sometimes used. The internal wiring is sometimes clamped to prevent contact with thermally hot
components. Reinstall all such elements to their original position.
3. After servicing, always check that the screws, components and wiring have been correctly reinstalled.
Make sure that the portion around the serviced part has not been damaged.
4. Check the insulation between the blades of the AC plug and accessible conductive parts(examples : metal
panels and input terminals).
5. Insulation Checking Procedure : Disconnect the power cord from the AC source and turn the power switch
ON. Connect an insulation resistance meter (500V) to the blades of the AC plug. The insulation resistance
between each blade of the AC plug and accessible conductive parts (see above) should be greater then 1
mega-ohm.
6. Never defeat any of the B+ voltage interlocks. Do not apply AC power to the unit(or any of its assemblies)
unless all solid-state heat sinks are correctly installed.
7. Always connect an instrument's ground lead to the instrument chassis ground before connecting the
positive lead; always remove the instruments ground lead last.

1-3 Precaution for Electrostatically Sensitive Devices(ESDs)

1. Some semiconductor("solid state") devices are easily damaged by static electricity. Such components are
called Electrostatically Sensitive Devices (ESDs); examples include integrated circuits and some field-
effect transistors. The following techniques will reduce the occurrence of component damage caused by
static electricity.
2. Immediately before handling any semiconductor components or assemblies. drain the electrostatic charge
from your body by touching a known earth ground. Alternatively, wear a discharging wriststrap device. (Be
sure to remove it prior to applying power-this is an electric shock precaution.)
3. After removing an ESD-equipped assembly. Place it on a conductive surface such as aluminum foil to
prevent accumulation of electrostatic charge.
4. Do not use freon-propelled chemicals. These can generate electrical charges that damage ESDs.
5. Use only a grounded-tip soldering iron when soldering or unsoldering ESDs.
6. Use only an anti-static solder removal device. Many solder removal devices are not rated as "anti-static;"
these can accumulate sufficient electrical charge to damage ESDs.
7. Do not remove a replacement ESD from its protective package until you are ready to install it. Most
replacement ESDs are packaged with leads that are electrically shorted together by conductive foam,
aluminum foil or other conductive materials.
8. Immediately before removing the protective material from the leads of a replacement ESD, touch the
protective material to the chassis or circuit assembly into which the device will be installed.
9. Minimize body motions when handling unpackaged replacement ESDs. Motions such as brushing clothes
together, or lifting a foot from a carpeted floor can generate enough static electricity to damage an ESD.
Rev. 2.00
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SRP-275