Identify potential hazards when working with computer equipment.

List the steps and potential hazards of discharging a Cathode Ray Tube (CRT).

Describe basic Electrostatic Discharge (ESD) procedures.

Discuss the potential risk of ESD to equipment.

Identify proper disposal methods for used computer equipment and consumables.

Always wear shoes with nonconductive rubber soles.

Do not wear leather-soled shoes or go barefoot when working on computer equipment.

Never assume that an electrical device is safe to handle.

Always test the device with a voltmeter. This is akin to the saying "Always assume that a gun is loaded."

Perform your tests with the device disconnected from the power source.

Some tests must be conducted with power applied. Be extremely cautious when performing these tests.

Always disconnect the power from a device when you are connecting or removing test leads.

This will prevent shorting the equipment by accidentally touching the lead to nearby components. Shorting can cause injury to you and/or damage to the equipment.

Do not wear jewelry of any kind.

Necklaces, rings, and bracelets can unintentionally short out nearby components when working in the tight space of most electronic cabinets. Make certain that earrings are removed. They may fall off and land on the electrical components you are testing.

Always discharge the large capacitors in equipment power supplies if you intend to remove the protective housing.

The power supply contains a capacitor, charged powerfully enough to be lethal, that is used to condition the power output.

Capacitors retain a charge even after the power cord is disconnected.

There are no user-serviceable parts inside of a power supply.

If you must work on a power supply, always double-check that the capacitor has been discharged with a reliable voltmeter or by shorting with an insulated screwdriver.

If at all possible, do not work on a circuit that is energized.

The CRT is vacuum sealed and, if broken, will implode, causing injury.

If you will be working on the interior of a monitor, discharge the CRT to prevent a lethal electric discharge.

Obtain a high voltage probe rated at 40,000 volts or higher.

Power off the monitor and let it set a few minutes to cool down.

Remove any rings or jewelry!

Remove the protective housing (cover) from the monitor.

Attach the ground lead of the high voltage probe to the metal chassis of the monitor.

Slide the tip of the high voltage probe under the rubber cover of the anode (positive) lead that connects to the CRT.

Printers are generally not considered to be dangerous pieces of equipment; however, they have areas within them that contain 110 VAC.

Certain parts of a printer can become very hot during operation. These include the print head on dot-matrix printers and the fuser assembly in laser printers.

Laser printers can pose the biggest hazard. The light generated by laser printers is not visible to the eye; however, the laser light can damage your eyes before you can realize what happened.

Fire in or around computer equipment is not a common occurrence.

Since a computer is an electrical device, you should use a Class C fire extinguisher, just as you would for any other electrical fire.

The best Class C fire extinguisher for use in a computer-related fire is a Class BC Halon or CO₂ extinguisher.

Alternatively, a Class BC Bisodium Powder fire extinguisher can also be used.

Equally important is humidity. If the humidity is too low, the risk of problems from ESD increase.

Water is the second most common cause of computer downtime and failure.

Dust is a significant concern for computer equipment.

Other potential hazards to computer equipment comes from power surges, brownouts, and other electric power problems.

Make sure the power outlet that the equipment is plugged in to is properly grounded and that the polarity is correct.

The use of a power protection device, such as a surge protector, power/line conditioner, standby power supply, or Uninterruptible Power Supply (UPS), is strongly recommended.

Surge protectors

Surge protectors are rated by clamping voltage and clamping speed.

Clamping voltage is the level of surge required before the device will attempt to suppress it.

Clamping speed is how quickly, after this voltage is reached, the protector will react.

The lower the clamping voltage, the more protection it provides.

Power/line conditioners

Line conditioners filter noise from the power lines and uses an isolation transformer to control both over voltages (surges) and under voltages (brownouts).

Backup power supplies

The backup power supply is the most effective way to guard against electrical problems.

There are two types of backup power supplies: Standby Power Supplies (SPS) and UPS.

Types of power supplies

SPS

UPS

A UPS also uses a battery to supply power to the system.

With a serial port connection, the UPS can communicate with the computer’s operating systems when a power failure occurs.

The watt rating of the UPS should always be larger than the cumulative watts drawn by the equipment that will be plugged in to the UPS.

Determine the volt-amps (VA) rating for your equipment.

Direct measurement

Use the equipment rating

Compare notes to others with the same setup you are using to determine the maximum VA rating.

Static electricity is created whenever two materials are rubbed together and electrons are transferred from one material to the other.

Human senses cannot detect a static electric charge of less than 2,500 volts.

Older Transistor-Transistor Logic (TTL) chips are more robust than the newer Complementary Metal Oxide Semiconductor (CMOS) chips.

To prevent destruction to components by ESD, static must be equalized between you and the equipment being serviced.

Static electricity will be more prevalent when the air is dry.

One of the most effective ways to prevent electron imbalance and ESD is to use a grounding strap.

The wire used on wrist straps has a resistor in it.

Keep all electronic components in their protective antistatic bags and foam until you are ready to connect them.

 

An ESD workstation consists of a conductive rubber mat and an ESD wrist strap.

Set up the ESD workstation by following these steps:

Place the conductive rubber mat on a suitable work surface.

Place the computer on the rubber mat.

Connect the wire (supplied with the mat) to the computer chassis. Be sure to connect it to the bare metal frame, not a painted surface.

Put on the wrist strap and connect it to the computer chassis.

ESD is caused by the discharge of static between you and sensitive computer components.

EMI is caused when electromagnetic energy is leaked into free space, forming a magnetic field that interacts with other electronic circuits or magnetic fields.

Some countries have begun to address the questions of computer equipment disposal and recycling.

Many communities have special environmental guidelines for the disposal of certain electronic components.

The CRT within a monitor can contain lead, mercury, barium, cadmium, and phosphorous, all of which are toxic substances.

Law prohibits corporations from dumping CRTs in landfills.

Several state and local governments also have laws regulating the disposal of CRTs by all individuals.

Many of these cartridges come with instructions for proper recycling.

If the cartridges do not come with recycling information, check with the manufacturer for proper disposal or recycling information.

Ensure that all expansion slot gaps are covered by a blanking plate so that dust does not enter the interior of the pc.

Gaps will disrupt the normal airflow produced by the pc’s cooling fan and cause components to overheat.

Use one of the following to clean the case :

Soft cloth moistened in water, dry cloth

A manufacturer-approved cleaning kit

A non-scratch household cleaner that does not contain ammonia

Do not use any spray cleaners near ventilation slots

 

 

Don’t use any volatile substances (benzene, thinners) to clean plastics

Only use approved cleaning fabrics because domestic cleaning cloths leave behind fibers that can clog mechanisms

The X and Y rollers of the mouse that produce horizontal & vertical movement of the mouse pointer can malfunction due to dirt (skin and sweat from your hand & dust) on them

Steps to clean a mouse :

Shut down the PC and disconnect the mouse cable

Remove the trackball cover on the underside & gently remove the trackball

Clean the trackball with a mild detergent and a soft cloth

Use a lint-free cloth or a special mouse cleaning kit to remove dirt from the rollers

Put the trackball back in the mouse & close the cover

Plug the mouse into the PC

 

 

Should be kept clean to avoid eyestrain

when using the pc for long periods of

time.

Steps to clean a monitor :

Turn off the PC

Unplug the monitor.

Dust the monitor by wiping the screen & cabinet with a soft, clean cloth.

May use an approved VDU screen cleaner.

Wipe horizontally across the screen then vertically, not forgetting the corners.

 

 

If an image remains on the monitor for very long it can become "burned" into the tube face

To prevent this from happening, use screen-saver

Do not use spray cleaners near monitor ventilation slots

Some monitors have anti-glare coatings or mesh filters that can only be cleaned with approved solutions & materials

Ensure that food & beverages are not present as these can cause the keyboard to malfunction should there be a spillage.

Steps to clean a keyboard :

Hold the keyboard with the keys facing slightly downward over a sheet of paper to catch the dirt

Use compressed air, a natural bristle brush or a PC vacuum cleaner to remove dust & dirt that’s fallen between the keys.

Don’t use foam cleaner as the foaming action can lift dirt particles & deposit them in the key switches.

Use a vacuum cleaner to remove dirt & dust from power supplies and fans.

This will improve the airflow through the unit & reduce ambient temperature levels.

Only approved PC vacuum cleaners should be used because domestic vacuum cleaners generate large amounts of static electricity, which is dangerous to the pc.

Safety guidelines for troubleshooting, installation, and maintenance tasks

Potential safety hazards when working with monitors and high voltage

Properly discharging a CRT

Types of fire extinguishers

Types of power protection devices, including surge protectors and backup power supplies

Potential hazards to computer equipment

The effects of ESD and EMI

The proper disposal of computer equipment