A Guide to PC Hardware Maintenance and Repair

1
Chapter 4 Computer Enclosures
2
Objectives

• Learn how enclosures are designed
• Develop an understanding of the different parts
  of the enclosure
• Become familiar with the terminology specific to
  the computer case

3
Form Factor

• Form factor is a function of the motherboard, the
  enclosure and the power supply
• ATX is the most common
• Older style AT cases are still found from time to
  time

4
Aspects of Form Factor

• Physical size and logical orientation of
  motherboard within the enclosure
• Physical and electrical design of the interface
  between the power supply and the motherboard
• Interface between the power switch and system
  board (or power supply, in the case of older
  designs)

5
Aspects of Form Factor (cont.)

• Size and shape of the circuit board used to
  manufacture the motherboard
• Positioning of screw holes used to position the
  motherboard (and other components)
• Positioning of externally accessible motherboard
  components to the enclosures backplane

6
A Timeline of Form Factors

• PC/XT
• No real fixed standards
• AT
• IBMs first attempt at standardizing cases and
  motherboards
• ATX
• Rotated the components on the board 90 degrees
  and put I/O connectors on the motherboard.

7
A Timeline of Form Factors (cont.)

• LPX
• Attempt to miniaturize the ATX, but with few
  standards
• NLX
• Standardized the Low Profile
• ITX
• Computer on a Card

8
Structure of the Enclosure

• Frame
• Case Cover
• Temperature Control
• Drive Bays
• The Front Panel
• The Backplane

9
The Frame

• Materials
• Aluminum
• Steel
• Impact of material on EMI resistance
• Impact of material on Cost

10
Case Cover

• U-cover
• Tongue in Groove
• Hinged Panel

11
Temperature Control

• Location and number of fans
• Proper use of backplane fillers
• Position and size of ventilation holes

12
Drive Bays

• To recap
• full-height
• half-height
• 1
• External
• Drive Rails
• Hot-swappable Drive Bays
• Internal
• Removable Drive Bays

13
Front Panel

• Power Switch
• Reset Switch
• USB ports (optional)
• Audio ports (optional)
• Power LED
• HDD LED

14
The Back Panel

• Voltage switch on power supply
• Serial ports
• Parallel port
• USB port
• Power connector
• Expansion slots

15
The Wiring Harness

• PWR ? Power
• RST ? Reset
• SPK ? Speaker
• TRB ? Turbo (when present)
• HDD ? Hard drive LED