Servicing Precautions; Esd Precautions - Samsung ML-5000A Service Manual

Precautions

1-2 Servicing Precautions

Note :
Requirements for AC power are described on the label
affixed to the rear of the printer. Check the AC voltage
rating requirement before use.
1. Before disassembly, pull the power plug from the AC
power connector.
2. To avoid spilling toner inside the machine, do not
turn the printer over or on its side before removing
the developer cartridge.
3. Faulty installation of DRAMs may cause permanent
damage to the Laser Printer.
4. Use only+5V power for video controller-related
circuitry.
5. When replacing parts, use only the same type of part
as the original. Replacing components with a second
vendorÕs part may cause faulty operation.

1-3 ESD Precautions

Some semiconductor (Òsolid stateÓ) devices are easily damaged from static electricity. Such components
commonly are called Electrostatically Sensitive Devices (ESDs); examples include integrated circuits (ICs),
Large-Scale Integrated circuits (LSIs), some field-effect transistors, and semiconductor chip components. The
following techniques will reduce the occurrence of component damage caused by static electricity:
CAUTION : Be sure the power is off to the
chassis or circuit board, and
observe all other safety precautions
1. Immediately before handling any semiconductor
components 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 the strap before applying power to
the unit under test to avoid potential shock.)
2. After removing ESD-equipped assembly, place it on a
conductive surface such as aluminum foil to prevent
accumulation of an electrostatic charge.
3. Do not use freon-propelled chemicals. These can
generate electrical charges sufficient to damage ESDs.
4. Use only a ground-tip soldering iron when soldering
or desoldering ESDs.
5. Use only anti-static solder removal device. Some
solder removal devices are not rated as Òanti-
static;Óthese can accumulate sufficient electrical
charge to damage ESDs.
1-2
6. Check the insulation between the blades of the AC
plug and accessible conductive parts (examples :
metal panels and input ports).
7. Insulation Checking Procedure:
Disconnect the power cord from the AC power
source. 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 left)
should be greater than 1 megaohm.
8. 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.
9. Always connect a test instrumentÕs ground lead to the
instrument chassis ground before connecting the
positive lead; always remove the instrumentÕs ground
lead last.
6. Do not remove a replacement ESD from its protective
package until you are ready to install it. Most
replacement ESDs are package with leads that are
electrically shorted together by conductive foam,
aluminum foil or other conductive materials.
7. 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.
8. Minimize body motions when handling unpackaged
replacement ESDs. Motion such as your clothes
brushing together, or lifting a foot from a carpeted
floor can generate enough static electricity to damage
an ESC.
9. Handle ICs and EPROMs carefully to avoid bending a
pin.
10. Pay attention to the direction of parts when mounting
or inserting them on a PCB.
11. Components can be permanently damaged if heated
for longer than necessary while welding. All
components are susceptible to heat damage.
Samsung Electronics