Like most electrical equipment, computer equipment can be dangerous, and you or others can be injured or even killed if you don’t follow proper safety guidelines when working on the equipment. Below, we list general precautions you should take before working with any computer equipment, followed by some specific areas of concern.
Always work with someone else if possible, even if the person is not a skilled technician. This person could at least be informed to call 911 and to shut down the power breaker if necessary.
Wear goggles or some other protective eye wear.
Wear shoes with non-conductive rubber soles to help reduce the chance of being shocked or seriously injured in an electrical accident.
Always test equipment with a Volt/Amp meter before working with it. Three or more Amps can seriously injure or kill a human being.
Do not work on components that are plugged into their power source. Exercise extreme caution when testing equipment that must be plugged in.
Do not remove expansion cards from a computer when it is turned on. The only exception is hot-swappable PC Card devices. Hot-swappable devices should be advertised or labeled as such. If in doubt, do not remove or add an expansion card while the power is on.
Remove all jewelry when working inside any computer related equipment.
Be sure not to mix electronic components and water. Because water is conductive, standing on a wet or freshly mopped floor is not appropriate when working with computers. Neither is a drink, of any kind, on the surface where you are working or standing.
If a fire occurs, make sure you use the right kind of fire extinguisher.
Class A: For wood, paper, cloth, plastics, and solid materials that are not metal.
Class B: For flammable liquids, such as gasoline, oil, grease, alcohol, and acetone.
Class C: For electrical components such as computers, printers, and monitors.
Class D: For metal such as sodium, aluminum, steel, magnesium, and potassium.
Power Supply
The power supply is connected to 120 volts AC and provides 5 and 12 volts DC out. When working with electronics, the risk of shock is always present. The power supply can store an electrical charge in the capacitors of the power supply even when the computer is turned off or unplugged. Be sure to observe proper safety procedures and exercise caution when testing the power supply.
High-Voltage Equipment
The CRT in a color monitor is powered by 25,000 volts of electricity. This high voltage presents a greater chance for bodily injury if you don’t use proper technique and caution. You should not wear metal jewelry when working with high-voltage equipment. Special high-voltage probes are available for use with your multi-meter and you should use them if you test the CRT voltage.
The CRT acts like a capacitor and can become charged when it’s not in use. Never touch the high-voltage anode near the front of the CRT, because it can give you an electric shock. Do not use an ESD grounding strap when working on the internal parts of a monitor, like the CRT, because you could receive a deadly shock.
Laser Printers
Two laser printer components — the toner’s fuser assembly and the laser — pose unique injury concerns. The toner that provides the image on the paper must be fused to the paper. The fuser assembly reaches a temperature of about 600 degrees and can cause severe burns. The laser in a laser printer can cause eye damage. Several safety switches are designed into laser printers to help ensure that the laser is disabled when the printer is open. However, when you work on laser printers, be aware that lasers are in use and can cause eye damage.
ENVIRONMENTAL CONCERNS
Material Safety Data Sheets (MSDS)
Electrostatic Discharge (ESD)
ESD protection gear
When disposing of computer equipment and related components, check to see whether the components are recyclable or listed as a hazardous material. Materials handling and disposal can be regulated at the federal, state, and local levels of government. You should be able to find information about hazardous material disposal from the environmental or purchasing group at your company.
Batteries, toner cartridges, ozone filters, CRTs, and empty compressed-air cans are examples of items that either can be recycled or may require special disposal procedures.
Materials that are considered hazardous material have handling and disposal sheets on record that detail disposal requirements. The environmental staff at a company is always happy to provide information about disposal of hazardous materials.
MSDS
Material Safety Data Sheets (MSDS) are provided with each product that you purchase if the product is considered a hazardous material. Batteries, compressed air cans (cans that contain CFCs), toner cartridges, ozone filters, and CRTs are all materials that need proper disposal handling.
The MSDS provides information for using and disposing of hazardous materials. If in doubt, refer to your environmental or purchasing group for MSDS information. The purchasing group in larger companies usually requires the vendor to provide MSDS sheets on all hazardous materials.
Be sure to follow proper disposal techniques for the following computer-related items:
CRTs
Batteries
Toner cartridges
Cleaning products (including compressed air)
Laser printer ozone filters
Electronic circuit boards and components
ESD
Almost anyone who has lived in a dry climate (with less than 70 percent humidity) has experienced electrostatic discharge (ESD). Most people experience ESD as an electric shock when they touch a metal object or another person. For a person to notice this shock, the voltage must be about 3,000 volts. Normal movements such as walking across a carpeted floor or lifting a chair can create a static charge, and it is easy to build up a damaging charge without realizing it. Small electronic components, such as microchips, are susceptible to damage from ESD. These components can be degraded or destroyed by ESD discharges as low as 10 to 20 V. A 10 V static discharge through a 5 V device can destroy the device.
Novell, Inc., a network operating system manufacturer, says of ESD that “about 90 percent of the time, ESD events cause the component to degrade, but not fail testing procedures, resulting in failure at a later date. Because components do not fail immediately, technicians often underestimate the cost of not using ESD prevention measures.”
Some Integrated Circuits (ICs) are more prone to being damaged by ESD than other components. For example, the CMOS chip is more prone to damage from ESD than most other components. Older, larger components such as Transistor-Transistor Logic (TTL) chips are less prone to ESD damage. Again, the denser, smaller objects used in the latest computer equipment are more prone to damage than earlier models.
I/O cards and memory are also very susceptible to ESD.
ESD Protection Gear
To reduce the chances of ESD, you should create an ESD-safe workstation. Figure 4.1 shows the equipment that can be used.
Conductive rubber mat, with a lead wire that can be connected to a metal surface to create a ground.
ESD wrist strap, which has a resistor inside the strap and a lead wire that can be connected to a metal surface as a ground. The grounding wire on the wrist strap should have between 1 and 10 Megaohms of resistance. The resistor should protect you in case you come in contact with a voltage source. If the resistor is bad or not included, the wrist strap is useless — an accidental shock could be serious and even deadly.
Table or workspace that is clean, clear of dust, and away from electrical machinery or other equipment that generates electrical currents.
The idea is to ensure that all components you are going to interact with have the same charge. By connecting everything to the computer case, you ensure that the components of the case, the chair, and your body all have the same charge. If every object has the same charge, the electrons will not jump from one object to another.
As important as knowing what ESD is and what ESD gear is available is knowing when to use ESD gear. You should use ESD gear when working with the computer components that are installed in the PC case, but never when working with the internal parts of the monitor.
Always use ESD gear when working with the parts of the PC that are housed in the case. If the PC is plugged in, the resistor in the ESD strap protects you from an electric shock.
Never use ESD gear when working with the internal parts of the monitor, especially the CRT. The CRT and high-voltage module could cause a deadly shock if the grounding strap comes in contact with either of these components.
Important: Never use ESD gear when working with the internal parts of a monitor and never remove energized computer boards while wearing an ESD.
TRANSPORTING AND STORING PARTS
ESD protection
Static bags
Temperature-controlled environment
Whenever you plan to transport electronic components, you should ensure that they will be safe from ESD. Always transport and store boards and ICs in static-shielding bags. The bags must be in perfect condition because even a small hole in the bag defeats the purpose of using the bag.
Be sure to notice the type of bag that is used. Anti-static bags and static-shielding bags are not necessarily the same. The pink or blue anti-static bags do not shield their contents from external static fields and should not be used. Static-shielding bags do protect their components from external static fields and usually have a gray/silver tint.
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