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Electricity and power systems. Unit objectives Measure and describe the characteristics of electricity Identify static electricity and follow ESD safe practices when working with computers Describe the purpose and features of power supplies and install a new power supply into a PC
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Electricity and power systems Unit objectives • Measure and describe the characteristics of electricity • Identify static electricity and follow ESD safe practices when working with computers • Describe the purpose and features of power supplies and install a new power supply into a PC • Troubleshoot faulty power supplies
Topic A • Topic A: Electricity and electronics • Topic B: Static electricity • Topic C: Power supplies • Topic D: Power supply troubleshooting
Electricity characteristics • Voltage • Current • Alternating or direct current • Resistance and impedance • Power and energy
Activity A-1 Examining the characteristicsof electricity
Electrical safety • Current can kill • The 1–10–100 rule • Calculating current V = i * r • Resistance of the human body
Safety precautions • Don’t touch exposed contacts • Touch only insulated handles of tools • Leave covers on equipment • Work one-handed • Don’t stick things into electrical sockets • Remove jewelry, watches, etc. • Keep hands clean and dry • Don’t work in wet surroundings
Activity A-2 Considering electrical safety
Using a multimeter • Measuring resistance • Measuring voltage • Measuring current • Measuring continuity
Activity A-3 Measuring electrical values
Topic B • Topic A: Electricity and electronics • Topic B: Static electricity • Topic C: Power supplies • Topic D: Power supply troubleshooting
Static electricity • Build up of charges • Static dangers • Discharge voltages • 3,000+ volts to feel • 8,000+ volts to see spark • 35,000 volts on a dry day on carpet • 1,000 volts can damage electronics
Prevent static build-up • Don’t shuffle your feet • Increase the humidity • Keep yourself grounded • Wear cotton, not synthetics • Remove carpeting • Use air ionization system
Prevent static discharge • Equalize charge differences safely • Unplug the equipment • Touch its metal chassis or power supply • Keep yourself and equipment connected • Wrist straps and anti-static mats • Static-safe bags
Typical internal components CD-ROM drive Power supply CPU / fan Adapter card Motherboard Hard drive
Slide catches Slide catch, move to open side of case
Determining which side to open Open this side to access components Ports and connectors attached to motherboard
Removable front cover Alignment posts Alignment holes Spring catches
Activity B-1 Opening the computer case while following proper ESD precautions
Topic C • Topic A: Electricity and electronics • Topic B: Static electricity • Topic C: Power supplies • Topic D: Power supply troubleshooting
Power_Good signal • Signals CPU that power is stable and sufficient • +5 V over specific wire • Must arrive at correct time
Peripheral power connector • “Molex” connector
Floppy power connector • “Berg” connector
SATA power connector • New, for Serial ATA drives
Wire colors • Yellow = +12 V • Red = +5 V • Black = ground
Activity C-1 Examining a power supply and connectors
Topic D • Topic A: Electricity and electronics • Topic B: Static electricity • Topic C: Power supplies • Topic D: Power supply troubleshooting
Troubleshooting symptoms • Computer fails to boot when powered on, but boots after pressing Ctrl + Alt + Delete • Computer intermittently stops working or reboots • You don’t have sufficient power connectors to connect all the devices you want to install • Computer fails to boot at all, with no lights or beeps; fans don’t start • Computer fails to boot, but fans start
Activity D-1 Troubleshooting power supply problems
Unit summary • Measured and described the characteristics of electricity • Identified static electricity and followed ESD safe practices when working with computers • Described the purpose and featurse of power supplies; and installed a new power supply into a PC • Resolved faulty power supply problems