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