Transcript A+ Computer Repair

A+ Computer Repair
Lesson 9
Problems Causing Power Events
Do Now
List all the items you use that require the
use of electricity.
Objectives
List and define common external power
problems
Describe electrostatic discharge
Define line noise and explain the problems
that this can cause
Common External Power
Problems
Improper grounding
Power surges
Power spikes or transients
Power sags or brownouts
Oscillations
Blackouts
Electrostatic Discharge
An electrostatic discharge (ESD) occurs
when one material carrying an
electrostatic charge transfers [because of
the force of attraction] that charge to
another material across a potential voltage
difference.
ESD!
An electrostatic discharge can also
occur between you and a computer if your
body is carrying an electrostatic charge
and comes into contact with a computer's
motherboard or components. Electrostatic
discharge can affect a computer
immediately or cause long term system
degradation.
Electromagnetic Interference
(EMI)
Electromagnetic Interference (EMI )
occurs when magnetic fields generated by
[electric] current-conducting wires in one
circuit influence neighboring magnetic
fields.
Radio Frequency Interference
(RFI)
Radio frequency line noise (RFI) occurs in
a computer and begins operating
erratically because it is picking up radio
transmissions from nearby electrical wires
or devices. RFI coming from a video
monitor or hard disk drive can be enough
to create computer system errors.
Improper Grounding
Proper grounding affects voltage, stability,
and is critical to personal safety.
Any time that a computer is not properly
grounded—an outlet is not providing a
wire connection to a ground—the
computer poses an electrical hazard and
could shock a user. When a user is
shocked by a computer, the user has
become the ground.
Power Surges
A power surge is a large, unexpected,
and sudden increase in electric voltage. A
surge can last for up to several seconds.
Consequences of electrical surges can be
severe and consist of lockups, a loss of
memory, problems in retrieving data,
altered data, garbling, damaged or
destroyed equipment.
Power Spikes
Also called transients, a spike is a sudden,
high-powered, voltage overload. Spikes
last briefly—between .5 and 100
microseconds. When a spike occurs, a
power line is hit with anywhere from 240 to
several thousand volts.
A spike is the equivalent of an electric tidal
wave entering equipment through AC
wiring and network, serial, or telephone
lines.
Power Sags
Also called brownouts, sags occur when
voltage falls 80% below normal capacity.
Sags commonly occur during hours of
peak use: when consumer power use is
high, circuits become overloaded, and
voltage decreases. Usually, when your
lamps flicker faintly, a brownout or sag has
occurred.
Consequences of Oscillations
More commonly called harmonic
distortion, oscillations are secondary
signals that occur on top of the 60-Hz
waveform.
Severe harmonic distortion can disrupt the
operation of a computer system.
What are the potential
consequences of blackouts?
What are the potential
consequences of blackouts?
Also called a power outage, a blackout is a
complete loss of electrical power.
Blackouts usually result from storms or
power company equipment failure. A
power outage during computer operations
can lead to data loss or corruption.