Safety

Outcomes  Potential health hazards when working with computer equipment.  Precautions to take to prevent injuries.  Steps and techniques for preventing ESD damage to computer equipment.  Proper grounding of computer equipment.  Electromagnetic interference (EMI).

Do  Turn off power before dismantling and unplugging  Touch case to discharge static electricity  Make sure you know what you are doing  Wear an anti-static wrist strap  Use power bars that are surge protected  Use proper tools  Always heed warning labels

Don’t  Attempt to repair without knowledge of computers  Eat or drink near computer  Exert excessive force on components  Open power supply or monitor  Use magnets (screwdrivers, pliers)  Touch components by their electrical contacts  Leave power bar on carpeting OR near flammable materials.

Electrostatic Discharge (ESD)

Electrostatic Discharge (ESD)  ESD is energy flow between two objects with different electrostatic potential  If no safe path is provided for this flow to occur, energy is released in the form of a spark as the two objects get closer.  Static potential is constantly generated by every move we make  The human body will notice discharges above 2000 Volts  a much smaller voltage may damage electronic components

Electrostatic Discharge (ESD)  All integrated circuits (ICs) or "chips" are very sensitive to ESD  RAM and CMOS chips are especially vulnerable  Damage may occur even when you don't feel it.  There are 2 types of damage that can occur

Immediate Failures  failures that occur immediately after the chip has been damaged  usually aren't recoverable until the chip has been replaced

Latent Failures  Sometimes a chip can be damaged by electrostatic discharge and the results aren't immediately noticeable  Months later the chip could finally fail completely  May end up with intermittent failures that occur sporadically

ESD Protection  Antistatic Wrist Straps  Fits on your wrist or is attached to the case or an anti-static mat  Antistatic Mats  provide a grounded surface on which to work or place components as you remove them  Some have a cord that can be plugged into a wall outlet to slowly remove any static charges

ESD Protection continued  Don't work on a computer or components when they are cold  Cold, dry conditions promote static electricity  Keep components and expansion cards inside their anti- static bags until you are ready to use them  handle them carefully, by their edges and as little as possible  Before you start working at the computer, touch the metal case to neutralize any potential static build-up  You may also use anti-static spray on the floor surrounding the area where you are working ReviewReviewAlso, see “check your understanding” Unit 1

Electrical Fires

Class C Fire Extinguisher  Class A - Wood, paper, cloth, trash and plastics. Solid combustibles that are not metals  Class B - Flammable liquids: gasoline, oil, grease and acetone. Any non-metal in a liquid state, on fire  Class C - Electrical: computers and printers. As long as it's "plugged-in," it would be considered a class C fire  Class D - Metals: potassium, sodium, aluminum and magnesium

Electromagnetic Interference EMI

 commonly produced by electric motors, loudspeakers, electrical lines, radios and cellular phones  can prevent proper transmission of data through network cables  can cause the PC to malfunction when attempting to communicate with other parts of the network  Similar problems could occur if a magnetic source is placed too close to a monitor

EMI vs ESD  EMI is recoverable or can be fixed  Removing the source of interference will correct EMI  ESD damage normally results in components having to be replaced

Safe Work area  A table top approximately 1x1.5 meters is usually sufficient  an anti-static mat for the technician to stand on, or for the computer case sit on (depending on the model)  adequate lighting  Testing equipment  tool kit  containers for storing components, screws, etc. (egg cartons work)  Shelves and storage cabinets  first-aid kit  Class C fire extinguisher

Warranties  Pay attention to warranty documents  a manufacturer may void the warranty if unqualified personnel work on it  might even void the warranty if anyone, other than the company's own technicians, opens the case