Computer Service and Repair

1
Computer Service and Repair

• Chapter 1 - Introduction

2
Objectives

• Explain the difference between digital and analog
  electrical signals
• Define an integrated circuit
• Explain the purpose of a computer
• Describe computer data
• Explain electrostatic discharge

3
Two Types of Electrical Signals

• Digital
• Best represented by a simple switch
• There can only be 2 conditions in the switch
  either on or off - (full voltage or no voltage)
• Example A typical lamp lamp is either on or
  off
• Digital electronics in computers use on and off
  conditions
• Analog
• Analog electronics use varying voltage levels
• Best represented by a dimmer switch
• Example A lamp with a dimmer switch the light
  can have different intensities because the switch
  varies the amount of electrical energy that
  reaches the lamp

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How does this apply to a computer?

• Computers are constructed of some vary complex
  digital circuits combined into modules such as
  circuit board cards.
• Technicians are responsible for replacing
  complete modules not repairing the digital
  circuits themselves.

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Integrated Circuits (Chips)

• A collection of electronic components
  (transistors and resistors) reduced to an
  unbelievable small size commonly found on circuit
  boards black squares or rectangles
• Example Over 6 million transistors manufactured
  as an IC can fit into the area the size of a dime

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What is a Computer?
What is Data?

• Information (words, images, music)
• Data is represented electronically as high and
  low voltages pulsed thru a computer system
• Data in a computer system is represented by 1s
  and 0s known as the binary system- think Morse
  Code
• Like the light switch on1, off0
• Data is converted from electrical signals to
  magnetic patterns for storage on disks

• A computer is an assembly of electronic modules,
  that interact with software to create, modify,
  transmit, store and display data.

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Bits, Bytes, and Words

• Units of data based on the binary number system
• Bit a single binary unit of 1 or 0
• Byte is equal to 8 bits
• Word total amount of bytes a computer can
  process at one time
• Many computers can process 32 bits (4 bytes) or
  64 bits (8 bytes)

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How is Data Transferred?

• Serial Transfer
• Data is sent through a port one bit at a time in
  successive order
• Parallel Transfer
• Data is sent more than 1 bit at a time side by
  side 8 bits

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A Computers Worst Enemy

• Electro Static Discharge (ESD)
• Transfer of static electrical energy from one
  object to another
• ESD can destroy the miniature circuits inside a
  computer chip
• Avoiding ESD
• Grounding strap
• Antistatic bags
• Antistatic mats
• ALWAYS unplug the PC and touch the metal sides of
  the computer chassis before touching any
  component in the PC