Transcript ComputerAssembly

Assembly / Disassembly / Reassembly
Computers
Chapter Objectives
After completing this chapter you will:
• Understand how static electricity can damage a computer.
• Understand what type of equipment causes RFI and EMI.
• Know which tools a technician needs.
• Understand the importance of diagramming when disassembling a
computer.
• Be able to disassemble and reassemble a computer.
Disassembly Overview
• Seldom is it necessary to completely disassemble a computer, however
when a technician is first learning microcomputers, it can be both very
informative and fun.
• Sometimes disassembly is accomplished to perform a preventive
maintenance cleaning.
• Other instances where disassembly is helpful is in diagnosing a problem
of undetermined cause by removing components one by one or to
outside the case. It can also help with diagnosing grounding problems.
• Grounding – Occurs when motherboard or adapter isn’t properly
installed and a trace (metal line on the motherboard or adapter) touches
the computer frame and causes the adapter or other components to stop
working.
Electrostatic Discharge (ESD)
• ESD (ElectroStatic Discharge) – Occurs when stored up static
electricity is discharged in an instantaneous surge of voltage. ESD
damage is nonrecoverable and the most susceptible components are the
CMOS and RAM chips.
• Anti-static Wrist Strap – A strap connecting the technician to the
computer and that equalizes the voltage potential between the two to
prevent ESD. It is connected to a grounding post or a metal component
such as the power supply. Electronic symbol for ground is:
• Warning: A technician should NEVER wear an ESD wrist strap when
working inside a monitor because of high voltages!
Electrostatic Discharge (ESD)
Anti-Static Wrist Strap
Disassembly – Figure #1
EMI (Electromagnetic Interference)
• EMI (ElectroMagnetic Interference) – also called EMR
(ElectroMagnetic Radiation) is noise caused by electrical devices. Can
travel through electrical wires.
• RFI (Radio Frequency Interference) – Noises that occur in the radio
frequency range.
• Always replace the slot covers for expansion slots that are not being
used. This will keep out dust and improve the airflow inside the
computer.
Tools
 Having the proper tools to disassemble the computer can make the task
easier and prevent damage to computer components.
Reassembly
• Reassembly is easily accomplished if the user is careful and diagrams
properly during disassembly. Exercise care and reinstall all components
to their original location.
• Three major reassembly components are :
– Motherboards: have plastic connectors on the bottom called standoffs.
– Cables
– Connectors
• Standoffs – Plastic connectors on the bottom side of a motherboard that
attach it to the case and prevent it from being in contact with the metal of
the computer case.
Cables and Connectors
• Keyed – A connector or cable that has an extra metal piece that allows
correct connections.
• Pin 1 – Pin 1 on a cable should be connected to Pin 1 on the connector.
The colored stripe on the edge of the cable identifies Pin 1 on the cable.
– Pin 1 on an adapter will be stenciled beside the connector.
• Solder Joints – Solder connections on the back of motherboards and
adapters. Pin 1 solder joints on the back of connectors are square.
• Hot wire – Brings AC current from the power supply to the PC’s front
panel.
• Return wire – Returns AC current from the PC’s front panel to the power
supply.
Cables and Connectors
Ribbon Cable’s Pin 1
Disassembly – Figure #2
Cables and Connectors
Adapter’s Pin 1
Disassembly – Figure #3
Cables and Connectors
Disassembly – Figure #4
Cables and Connectors
Connector’s Pin 1
Disassembly – Figure #5
Cables and Connectors
Front Panel Power Switch Connections
Disassembly – Figure #6
Hard Drives
• Hard drives must be handled carefully during disassembly because of the
delicate nature of their very intricate construction.
– The read/write heads are located only millimeters from the platter
storing all the data. A small jolt can cause them to make contact with
the platter and cause permanent physical damage.
– Older hard drives had utility programs to park, or lock, the heads in
place away from the platters when not in use.
• Self-Parking Heads – Hard drives that have read/write heads which pull
away automatically when the computer powers off. This feature still
would not prevent damaged caused by an accident or mishandling.
Preventive Maintenance
• Preventive Maintenance – Certain procedures performed to prolong the
life of the computer, such as cleaning the computer, drive heads,
keyboard keys, printers, and monitor screen.
• MSDS (Material Safety Data Sheets) – Sheets that contain information
about a product, its toxicity, storage, and disposal.