Servicing Precautions - Sam4s ER-390 Series Service Manual

1 Precaution Statements

1-2 Servicing Precautions

WARNING: 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: An electrolytic capacitor installed with the wrong polarity might explode.
1. Servicing precautions are printed on the cabinet.
Follow them.
2. Always unplug the units AC power cord from the AC
power source 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
3. 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.
4. After servicing, always check that the screws,
components and wiring
reinstalled. Make sure that the portion around the
serviced part has not been damaged.
1-3 Precautions for Electrostatic Sensitive Devices (ESDs)
1. Some semiconductor (solid state) devices are easily
damaged by static electricity. Such components are
called Electrostatic Sensitive Devices
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 wrist-strap
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.
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.
1-2
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5. Check the insulation between the blades of the AC
plug and accessible conductive parts
(examples : metal panels and input terminals).
6. 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 AC plug.
The insulation resistance between each blade of the
AC plug and accessible conductive parts (see above)
should be greater than 1 megohm.
7. 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.
8. Always connect an instrument's ground lead to the
instrument chassis ground before connecting the
positive lead ; always remove the instrument's ground
lead last.
7. Do not remove a replacement ESD from its protective
package until you are ready to install it.
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,
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.
Most
touch the
SAM4S ER-390 SERIES