Servicing Precautions - Sam4s ER-260 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 have been correctly
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 (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 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. These can
generate electrical charges that damage ESDs.
5. Use only a grounded-tip soldering iron when
soldering or unsoldering ESDs.
1-2
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 mega ohm.
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.
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.
SAM4S ER-260 SERIES