SAFETY AND PREVENTIVE MAINTENANCE
Preventive maintenance involves performing certain practices
on a computer so that the
computer will function reliably and not fail as often.
Software utilities can make a
computer system faster and more efficient. There are
software related preventive
maintenance activities that can be automated.
Importance
• Saves money
• Saves time
• Safeguard data
• Improves performance
Important things to observe:
• Creating a schedule for regular maintenance will help keep
computer
devices running at an optimal level
• Every time a computer maintenance task is performed it
should be noted
in a maintenance log
• The best source for maintenance information is the
manufacturer’s
documentation.
1. Cleaning and preventative maintenance:
The cleanliness of a computer is extremely important.
Buildup of dust, dirt, and oils can
prevent various mechanical parts of a computer from
operating.
Computer components get dirty. Dirt reduces their operating
efficiency and, ultimately,
their life. Cleaning them is definitely important. But
cleaning them with the right
cleaning compounds is equally important. Using the wrong
compounds can leave residue
behind that is more harmful than the dirt you are trying to
remove!
First of all, most computer cases and monitor cases can be
cleaned using mildly soapy
water on a clean, lint-free cloth. Make sure that the power
is off before putting anything
wet near a computer. Dampen (not soak) a cloth in mild soap
solution and wipe the dirt
and dust from the case. Then wipe the moisture from the case
with a dry, lint-free cloth.
Anything with a plastic or metal case can be cleaned in this
manner.
Additionally, if you spill anything on a keyboard, you can
clean it by soaking it in
distilled, demineralized water. In this type of water, the
extra minerals and impurities
have been removed and so it will not leave any traces of
residue that might interfere with
the proper operation of the keyboard after cleaning.
The electronic connectors of computer equipment, on the
other hand, should never touch
water. Instead, use a swab moistened in distilled, denatured
isopropyl alcohol (also
known as electronics cleaner and found in electronics
stores) to clean contacts. This will
take oxidation off of the copper contacts.
Finally, the best way to remove dust and dirt from the
inside of the computer is to use
compressed air instead of vacuuming. Compressed air can be
more easily directed and
doesn’t easily produce ESD damage (like vacuuming could).
Simply blow the dust from
inside the computer using a stream of compressed air.
However, make sure to do this
outside so that you don’t blow dust all over your work area
or over yourself.
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Preventive Maintenance for Computer Peripherals
Monitor
Since the display unit is the most visible piece of computer
equipment, it should
be kept clean for both appearance and functionality. The
information in this
section applies to both CRT and LCD screen types.
When cleaning a display, make sure the device is unplugged
from the wall. Use a
damp cloth with a mild detergent to wipe down the entire
display unit and remove
any dust buildup. Dampen another cloth with water to remove
any cleaner
residue on the surface of the monitor. Avoid using too much
water to prevent
drips. After cleaning the display, use a dry cloth to
complete the job. Be careful
when cleaning to avoid scratching the screen portion of the
monitor.
Mice
Mice can be either mechanical or optical.
A mechanical mouse may not function properly if it becomes
dirty. When dust
settles on the mouse pad, it gets swept up into the moving
parts of the mouse.
This causes a buildup on the rollers inside the mouse. The
fastest way to clean it
is to remove the plate on the bottom of the mouse, remove
the ball, and then
gently scrape the dust buildup from the rollers. The buildup
can be removed with
a fingernail or another gentle scraping tool. Another
cleaning method is to use
isopropyl alcohol or methanol with a cotton swab.
An optical mouse may need to be cleaned with a damp cloth on
the optical
sensor surface. However, this could damage the mouse and
should only be done
if absolutely necessary. Be sure to unplug an optical mouse
before cleaning it.
Eyes should not be exposed to the laser.
Keyboard
A keyboard receives more physical abuse than any other
component of a
computer system. Keyboards are also exposed to the
environment, which allows
dust to build up on the keyboard over time. Periodic
cleaning of the keyboard will
prolong the lifespan and prevent malfunction. This allows
easy access to the
areas where dust collects. A soft brush or cotton swab can
be used to remove
dirt from under the keys. Compressed air can be used to blow
out dust from
below the keys. The keyboard should be held vertically or in
an inclined position
while using the air to blow out the dirt and dust. This will
prevent large dirt and
dust particles from remaining stuck in the interior corners,
springs, and foam
material beneath the keys.
Scanners
It is important to keep the scanner surface clean. If the
glass becomes dirty,
consult the user guide for manufacturer cleaning
recommendations. If the manual
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does not list any recommendations, use a glass cleaner and a
soft cloth to
protect the glass from getting scratched.
If the inside of the glass becomes dirty, check the manual
for instructions on how
to open the unit or remove the glass from the scanner. If
possible, thoroughly
clean both sides, and replace the glass as it was originally
set in the scanner.
Software utilities
There are several utilities included with DOS and Windows
that help maintain
system integrity. If used on a regular basis, the following
utilities can increase
system speed and efficiency:
• ScanDisk – This utility is used to check the integrity of
files and folders or
to thoroughly check the system by scanning the disk for
physical errors. It
can be used on any formatted disk that the operating system
can read.
This program should be used whenever the system is not
shutdown
properly or at least once a month.
• Defrag – When a program in installed on a computer, it may
be stored in
more than one place on the hard drive. This is known as
fragmentation.
Fragmentation lowers the performance of a drive. This
utility optimizes
space on the hard drive to allow programs to execute faster.
Technicians
will generally start Defrag after using the ScanDisk
utility.
• CHKDSK /f – This command is used to check the file system
for errors
and can be compared to the ScanDisk for Windows 2000 and XP.
CHKDSK is a DOS application that runs on the command line.
REGEDIT – The Registry is a database that holds
configuration data about the
hardware and environment of the PC. REGEDIT is a command
used by
advanced technicians. It provides access to the Registry in
a view similar to
Windows Explorer. If anything is changed in the Registry, it
could result in system
errors or malfunctions. Changes cannot be undone, so extreme
caution is
advised when using this program.
Anti-virus
Computer viruses are programs that have been written by
people with malicious
intent. After a computer has been infected, the virus can be
spread to other
machines through a network connection or by removable media.
An anti-virus application can be used to prevent a virus
from infecting the system.
Anti-virus programs can also be run on command and scan the
entire computer
or a specific file for viruses. If a virus is found, the
anti-virus software will either
clean the infected file or isolate the file. If a file
becomes isolated, the user will
not be able to open it. The anti-virus program must be
updated often or
automatically updated.
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Viruses are typically sent as e-mail attachments. After
being opened, the virus
will infect the computer and send itself out using e-mail
addresses found in
programs such as Microsoft Outlook. Other users will assume
that the e-mail is
legitimate, which will allow the virus to spread. Be
suspicious of e-mail
attachments with .exe extensions. When in doubt, contact the
sender before
opening an attachment.
If a computer system is behaving strangely and the hardware
checks out, a virus
may still exist. The virus can act like a hardware failure.
If anti-virus software is
installed, run it to make sure the system is clean and then
schedule it to run on a
regular basis.
2. Power issues
Computers components are vulnerable to various kinds of
electrical fluctuations.
The delicate internal components can be damaged by
electrical discharges.
Computers can be damaged or destroyed by high levels of
electrical releases
such as lighting or low levels such as static electricity.
The following types of
power interruptions can cause a system to malfunction or
fail:
• Blackouts – Blackouts are the complete loss of power for
any amount of
time. They are usually caused by weather-related events such
as high
winds, lightning, or earthquakes.
• Brownouts or Sags – Brownouts are a drop in power. Sag is
a brownout
that lasts less than a second. These incidents occur when
voltage on the
power line falls below 80 percent of the normal voltage.
This can be
caused by overloaded circuits. Utility companies may
intentionally cause
brownouts to reduce the power drawn by users during
peak-demand
periods. Sags and brownouts account for a large proportion
of the power
problems that affect networks and computing devices.
• Noise – Noise is caused by interference from radio
broadcasts,
generators, and lightning. Noise results in unclean power,
which can
cause errors in a computer system.
• Spikes – Spikes are sudden increases in voltage that are
much higher
than normal levels. For example, if the event lasts one or
two seconds, it
is called a spike. These are usually caused by lightning
strikes but can
also occur when the utility system comes back online after a
blackout.
• Power Surge – A power surge is a dramatic increase in
voltage above the
normal flow of electrical current. Power surges are also
referred to as
transient voltage. If a standard wall outlet in the United
States increases
from 120 V to 250 V, this is a power surge. A power surge
lasts more than
3 nanoseconds. A nanosecond is one-billionth of a second.
Surge
suppressors can help protect delicate computer components
from power
surges.
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An understanding of the different power issues that can
affect computer systems
will simplify the prevention of problems. The next section
will discuss the devices
that can be used to protect computer equipment from power
issues.
Surge suppressor and power supplies
This section introduces different devices, which can be used
to protect sensitive
computer equipment from power issues.
Line Conditioners
Line conditioners work by filtering and smoothing the power
stream to eliminate dips,
fluctuations and interference that can cause power to be
"noisy". Their ability to reduce
noise is measured in decibels over a given frequency range
(just like noise reduction in
your home stereo system). The more noise reduction, the
better. Good line conditioners
can be quite costly due to the high quality of components
required to do the best job. In
some ways, a surge suppressor can be consider the "poor
man's line conditioner".
Surge suppressors
Surge suppressors, which are also called protectors, can
help guard against
electrical surges and spikes by diverting extra voltage to
the ground. Surge
suppressors use a component called a Metal Oxide Varistor
(MOV) to divert the
over-voltage. A clamping voltage triggers the MOV. If the
voltage is above the
minimum, it is diverted to the MOV and bypasses the computer
components.
This ensures that the voltage going to a device stays below
a certain level.
Protectors are mainly used to stop spikes from zapping the
hardware. They also
prevent high-voltage power surges from damaging computer
equipment. Surge
suppressors usually have a built-in fuse that prevents
excess amounts of power
from flowing through the unit. However, a surge suppressor
is useless during
brownouts or blackouts.
Standby Power Supplies (SPSs)
A standby power supply (SPS) has a backup battery to supply
power when the
incoming voltage drops below the normal level. The battery
is on standby during
the normal operation of the unit. When the voltage slips,
the battery provides DC
power to a power inverter, which converts it to AC power for
the computer. The
problem with this device is the time it takes to switch over
to the battery. If the
switching device fails, the battery will not be able to
supply power to the
computer.
Uninterruptible Power Supplies (UPSs)
An uninterruptible power supply (UPS) is comparable to SPS.
However, a UPS
requires battery power to operate. The power entering the
unit recharges the
batteries while they are in use. The power from the battery
is sent to an inverter,
which sends AC power to the computer. This device protects
against AC power
issues. A UPS provides a limited supply of power during a
power failure. A UPS
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usually provides enough time to save and exit before the
lack of power causes
the machine to turn off. A UPS can also help guard against
power sags or
brownouts. Most people prefer to use a UPS over an SPS
because of the
switching time involved with an SPS. A UPS provides a steady
stream of power
with no delay.
• Overall, the best protection against power issues is a
properly grounded
building with enough battery power to run all equipment in
case of a power
outage.
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3. HIGH VOLTAGE EQUIPMENT
The Computer
If you have to open the computer to inspect or replace parts
(as you will with most
repairs), be sure to turn off the machine before you begin,
and be sure to read the next
section, which covers safety issues with the power supply.
The computer case is metal
with sharp edges, so be careful when handling it. You can,
for example, cut yourself by
jamming your fingers between the case and the frame when you
try to force the case back
on.
POWER SUPPLY
Although it is possible to work on a power supply, it is not
recommended. Power supplies
contain several capacitors that can hold lethal charges long
after they have been
unplugged! It is extremely dangerous to open the case of a
power supply. Besides, power
supplies are inexpensive, so it would probably cost less to
replace them than to try to fix
them, and it would be much safer.
The Monitor
Other than the power supply, one of the most dangerous
components to try to repair is the
monitor, or Cathode Ray Tube (CRT). In fact, we recommend
that you do not try to
repair monitors. To avoid the extremely hazardous
environment contained inside the
monitor—it can retain a high-voltage charge for hours after
it’s been turned off—take it
to a certified monitor technician or television repair shop.
The repair shop or certified
technician will know and understand the proper procedures to
discharge the monitor,
which involve attaching a resistor to the flyback
transformer’s charging capacitor to
release the high-voltage electrical charge that builds up
during use. They will also be able
to determine whether the monitor can be repaired or needs to
be replaced. Remember, the
monitor works in its own extremely protective environment
(the monitor case) and may
not respond well to your desire to try to open it.
Even though we recommend not repairing monitors. If you have
to open a monitor, you
must first discharge the high-voltage charge on it using a
high-voltage probe. This probe
has a very large needle, a gauge that indicates volts, and a
wire with an alligator clip.
Attach the alligator clip to a ground (usually the round pin
on the power cord). Slip the
probe needle underneath the high-voltage cup on the monitor.
You will see the gauge
spike to around 15,000 volts and slowly reduce to zero. When
it reaches zero, you may
remove the high-voltage probe and service the high-voltage
components of the monitor.
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