The power supply takes electricity from the wall and transforms it into lower voltages to power computer components. It provides power to the motherboard via a 20- or 24-pin connector and to peripherals like hard drives via Molex, SATA, and other connectors. Power supplies come in different form factors and wattages must match the needs of the system. Proper grounding and surge protection helps prevent damage from power issues.

1. Power Supplies

2. Power Supplies
 Takes electricity from the wall socket
and transforms it into electricity to run
the motherboard and other internal
components
EXAM TIP Some questions on the CompTIA A+ certification
exams could refer to a power supply as a PSU, for power
supply unit. A power supply also falls into the category of field
replaceable unit (FRU), which refers to the typical parts a tech
should carry, such as RAM and a floppy disk drive.

3. Understanding Electricity
 The pressure of the electrons in the wire is called
voltage and is measured in units called volts (V)
 The amount of electrons moving past a certain
point on a wire is called the current or amperage,
which is measured in units called amperes (amps or
A)
 The amount of amps and volts needed by a
particular device to function is expressed as how
much wattage (watts or W) that device needs
 The correlation between the three is : V × A = W

4. Common Electrical
Components

5. Circuit Breaker
 Circuit breakers and ground wires provide the basic protection
from accidental overflow
 A circuit breaker is a heat-sensitive electrical switch rated at a
certain amperage
 If you push too much amperage through the circuit breaker,
the wiring inside will detect the increase in heat and
automatically open, stopping the flow of electricity before the
wiring overheats and breaks
 You reset the circuit breaker to reestablish the circuit and
electricity will flow once more through the wires
 A ground wire provides a path of least resistance for electrons
to flow back to ground in case of an accidental overflow
EXAM TIP An electrical outlet must have a ground
wire to be suitable for PC use!

6. Hot, Neutral, and Ground
(continued)

7. Hot, Neutral, and Ground
(continued)

8. Multimeter
 A multimeter—often also referred to as a volt-ohm
meter (VOM) or digital multimeter (DMM)—
– Enables you to measure a number of different aspects of
electrical current
– Provides at least four major measurements: AC voltage,
DC voltage, continuity, and resistance
 A multimeter consists of two probes:
– An analog or digital meter, and a dial to set the type of
test you want to perform

9. UPS
 UPS - uninterruptible power supply
(UPS)
– Protects your computer (and, more
importantly, your data) in the event of a
power sag or power outage
– A UPS essentially contains a big battery
that will provide AC power to your
computer, regardless of the power
coming from the AC outlet

10. Uninterruptible Power
Supplies
 Benefits
– Condition line for brownouts and spikes
– Provide backup power during a blackout
– Protect against very high potentially damaging
spikes
 Considerations
– Cost
– UPS rating
– Degree of line conditioning
– Warranty and service policies

11. Power Supplies
 The power supply unit (PSU) takes over,
converting high-voltage AC into several DC
voltages (notably, 5.0, 12.0, and 3.3 volts)
usable by the delicate interior components
 PC uses the 12.0-volt current to power
motors on devices such as hard drives and
CD-ROM drives, and it uses the 5.0-volt and
3.3-volt current for support of onboard
electronics

12. Power Supplies

13. Power to the Motherboard
 Use a 20- or 24-pin P1 power
connector. Some motherboards may
require special 4-, 6-, or 8-pin
connectors to supply extra power

14. Power to Peripherals:
Molex
 Molex Connectors
– The most common type of power
connection for devices
– Need 5-volts or 12-volts of power is the
Molex connector
– The Molex connector has notches, called
chamfers, that guide its installation

15. Power to Peripherals:
Mini Connectors
 Mini Connectors
– A second type of connector, called a mini
connector
– Supplies 5 and 12 volts to peripherals,
although only floppy disk drives in
modern systems use this connector

16. Power to Peripherals:
SATA Power Connectors
 SATA Power Connectors
– Serial ATA (SATA) hard drives need a special 15-
pin SATA power connector
– The larger pin count supports the SATA hot-swappable
feature, and 3.3 V, 5.0 V, and 12.0 V
devices. SATA power connectors are L shaped,
making it almost impossible to insert one
incorrectly into a SATA drive
– No other device on your computer uses the SATA
power connector

17. Power to Peripherals:
Splitter & Adapters
 Not enough connectors to power all of
the devices inside your PC
– Purchase splitters to create more
connections

18. Power to Peripherals:
Auxiliary Connector
 Motherboard power connector
– Commonly called an AUX connector
– To supply increased 3.3- and 5.0-volt
current to the motherboard

19. Power Supply Form
Factors
 All use standard ATX connectors, but differ
in size and shape from standard ATX power
supplies
– TFX12V A small power form factor optimized for
low-profile ATX systems
– SFX12V A small power form factor optimized for
systems using FlexATX motherboards
– CFX12V An L-shaped power supply optimized
for Micro BTX systems
– LFX12V A small power form factor optimized for
low-profile BTX systems

20. Protecting Your Computer
System: General Precautions
 Make notes so you can backtrack
 Remove packing materials from work
area
 Keep components away from hair and
clothing
 Keep screws and spacers in an orderly
place

21. Protecting Your Computer
System: General Precautions
 Don’t touch chips on motherboard or
expansion cards
 Don’t touch chip with magnetized
screwdriver
 Don’t change DIP switch settings with
a graphite pencil

22. Protecting Your Computer
System: General Precautions
 Have classroom instructor check your
work before putting cover on and
powering up
 Turn off a computer before moving it
 Keep disks away from magnetic fields,
heat, and extreme cold

23. Protecting Yourself
Against Electricity
 Turn off power and unplug computer
 Always use a ground bracelet
 Never touch inside of a computer
while it is turned on
 Never remove cover or put your hands
inside monitor or power supply

24. Static Electricity (or ESD)
 Can cause catastrophic failure or upset
failure
 Protection against ESD
– Ground bracelet or static strap
– Ground mats
– Static shielding bags

25. Ground Bracelet

26. EMI
(Electromagnetic Interference)
 Caused by magnetic field produced as
side effect when electricity flows
 Protection against EMI
– Cover expansion slots
– Do not place system close to or on same
circuit as high-powered electrical
equipment
– Use line conditioners

27. Upgrading Your Power
Supply
 Sometimes necessary when you add
new devices
 Easiest way to fix a power supply you
suspect is faulty is to replace it

28. Introduction to
Troubleshooting
 Isolate the problem
– Problems that prevent PC from booting
– Problems that occur after a successful
boot
 Learn as much as you can by asking
questions of user(s)

29. PC Problem Solving

30. Troubleshooting the Power
System: General Guidelines
 Any burnt parts or odors?
 Everything connected and turned on? Loose
cable connections? Computer plugged in?
 All switches turned on? Wall outlet good?
 If fan is not running, turn off computer:
Connections to power supply secure? Cards
securely seated?

31. Troubleshooting the Power
System: General Guidelines
 Check for correct wire connections to
motherboard
 Remove nonessential expansion cards
one at a time
 Vacuum entire unit

32. Troubleshooting an ATX
Power Supply

33. Troubleshooting the
Power System
 Power supply itself
 Power supply fan
 Power problems with the motherboard
 Overheating

34. Preventing Overheating

35. Preventing Overheating
(continued)

36. Energy Star Systems
(The Green Star)
 Satisfy energy-conserving standards of
the US EPA
 Generally have a standby program that
switches device to sleep mode when
not in use
 Apply to computers, monitors,
printers, copiers, and fax machines

37. Power Management
Methods
 Advanced Power Management (APM)
 AT Attachment (ATA) for IDE drives
 Display Power Management Signaling
(DPMS) standards for monitors and
video cards
 Advanced Configuration and Power
Interface (ACPI)

38. Power Management
Features
 Green timer on the motherboard
 Doze time
 Standby time
 Suspend time
 Hard drive standby time

39. Power Management
Setup Screen

40. Energy Star Monitors
 Most adhere to DPMS specifications
– Allow video card and monitor to go into
sleep mode simultaneously

41. Changing Power Options