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Chapter 4 • Disassembly and Power
Figure 4.32 Line conditioner
Uninterruptible Power Supply (UPS)
A UPS (uninterruptible power supply), sometimes called an online (or true) UPS or a line
interactive UPS, provides power to a computer or other device for a limited amount of time
when there is a power outage. A UPS provides enough time to save work
and safely shut down the computer. Some operating systems do not oper-
ate properly if power abruptly cuts off and the computer is not brought
to a logical stopping place. A network server, the main computer for a
network, is a great candidate for a UPS. Network operating systems are
particularly susceptible to problems during a power outage. Some UPSs
have a connection for a cable and special software that automatically
maintains voltages to the computer, quits all applications, and powers off
the computer. Some UPS units have USB and/or network connections as
well.
A UPS also provides power conditioning for the devices attached to
it. The AC power is used to charge a battery inside the UPS. The battery
inside the UPS supplies power to an inverter. The inverter makes AC for
the computer. When AC power from the outlet fails, the battery inside
the UPS continues to supply power to the computer. The battery inside
the UPS outputs DC power, and the computer accepts (and expects) AC
power. Therefore, the DC power from the battery must be converted to
AC voltage. AC voltage looks like a sine wave when it is in its correct
form, but cheaper UPSs produce a square wave (especially when power
comes from the battery) that is not as effective. Some computer systems
and peripherals do not work well on a 120VAC square wave, modified sine
wave, or quasi-sine wave. Figure 4.33 illustrates a sine wave and a square wave.
A UPS can be the best protection against adverse power conditions because it protects
against overvoltage and undervoltage conditions, and it
provides power so a system can be shut down properly.
When purchasing a UPS, be sure that (1) the amount
of battery time is sufficient to protect all devices; (2)
the amount of current the UPS produces is sufficient
to protect all devices; and (3) the output waveform is a
sine wave.
Sine wave
Square wave
Figure 4.33 Sine wave and
square wave
Do not plug a laser printer into a UPS
unless it has a rating less than 1400VA
Most UPSs cannot handle the very high current
requirements of a laser printer.
Tech
Tip
- Guide to PCs 2
- Complete CompTIA 3
- Contents at a Glance 4
- Contents 10
- Contents 11
- About the Author 19
- Dedication 20
- Acknowledgments 20
- We Want to Hear from You! 21
- Reader Services 21
- It Pays to Get Certified 22
- CompTIA Career Pathway 23
- Steps to Certication 23
- Content Seal of Quality 24
- Why CompTIA? 24
- Introduction 25
- Organization of the Text 26
- Features of This Book 27
- IT work 31
- CompTIA A+ Exam Objectives 32
- CompTIA Exam Objectives 33
- Disassembly 36
- Disassembly Overview 37
- Electrostatic Discharge (ESD) 37
- Opening the Case 41
- Cables and Connectors 41
- Snug connections 43
- Storage Devices 45
- Motherboards 46
- Mobile Device Issues 47
- Reassembly 49
- Preventive Maintenance 49
- Basic Electronics Overview 51
- Electronics Terms 51
- Good connection Broken wire 53
- Power Supply Overview 54
- Power Supply Form Factors 55
- Tech Tip 56
- Purposes of a Power Supply 58
- Power Supply Voltages 60
- Mobile Device Power 61
- Keep Li-ion batteries cool 63
- Power Interface) 64
- Windows power management 65
- Watch the wattage 68
- Solving Power Supply Problems 70
- Adverse Power Conditions 71
- Adverse Power Protection 72
- Surge Protectors 72
- Line Conditioners 74
- Figure 4.32 Line conditioner 75
- Figure 4.33 Sine wave and 75
- Standby Power Supply (SPS) 77
- Electrical Fires 78
- Computer Disposal/Recycling 79
- Chapter Summary 81
- Review Questions 82
- Exercises 85
- External Cables 86
- Computer Case Removal 86
- Adapter Placement 86
- Motherboard 88
- Lab 4.3 Amps and Wattage 89
- Lab 4.4 Continuity Check 89
- Lab 4.5 Pin-Out Diagramming 90
- Lab 4.6 Fuse Check 91
- Lab 4.7 Using a Multimeter 91
- Figure 4.38 AC outlet 93
- GND to hot 120VAC 93
- GND to neutral 0VAC 93
- Hot to neutral 120VAC 93
- +5 volts 95
- +12 volts 95
- Activities 97
- Critical Thinking Skills 99
- A+ Certification Exam Tips 99
- Complete PC Restore tool 107
- FireWire 114
- IRQs (Interrupt Requests) 120
- PBs (petabytes) 129
- Setup program 136
- SSDs (solid state drives) 138
- SSDs (solid state drives) 139
- TBs (terabytes) 140
- troubleshooting 143
- video 145
- Windows 147
- Windows Vista 148
- Windows Vista 149
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