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Assembly / Disassembly / Reassembly

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.

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Assembly / Disassembly / Reassembly

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  1. Assembly / Disassembly / Reassembly Computers

  2. 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.

  3. 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.

  4. 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!

  5. Electrostatic Discharge (ESD) Anti-Static Wrist Strap Disassembly – Figure #1

  6. 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.

  7. Tools • Having the proper tools to disassemble the computer can make the task easier and prevent damage to computer components.

  8. Reassembly • Reassembly iseasily 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.

  9. 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.

  10. Cables and Connectors Ribbon Cable’s Pin 1 Disassembly – Figure #2

  11. Cables and Connectors Adapter’s Pin 1 Disassembly – Figure #3

  12. Cables and Connectors Disassembly – Figure #4

  13. Cables and Connectors Connector’s Pin 1 Disassembly – Figure #5

  14. Cables and Connectors Front Panel Power Switch Connections Disassembly – Figure #6

  15. 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.

  16. 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.

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