1. Power Supply

2. Purpose of the Power Supply
Convert household power into a form the computer can use.
Provides power to every device in the computer.
The Power Supply converts AC (alternating current) which is external power to DC (direct current) internal power that the computer can use.
Link to AC/DC Voltage Conversion Information
How Computer Work Video (Old Version) – video clip on the power supply.

3. Roles of the Power Supply
Stability – provides sufficient power to PC.
Cooling - The power supply contains the main fan that controls the flow of air through the PC case.
Energy Efficiency - Newer PC power supplies work with components to reduce the amount of power they consume when idle.
Expandability - The capacity of your power supply is one factor that will determine your ability to add new drives to your system
A power supply is responsible for 28% of computer problems and is 2% of the computer cost.

4. Household Power & Problems
Household Power – the external power source that comes into the wall.
Power Problems that may lead to power supply problems.
Line Noise
Surges
Lightening strikes
Brownouts
Blackouts
Link to Household Power and Problems

5. Line Noise
Line Noise - Line noise consists of small variations in the voltage level delivered to the computer. Noise that the power supply cannot handle can cause it to malfunction and pass the problem on to your motherboard or other internal devices

6. Surges
This is a temporary increase of voltage that can last just a few thousandths of a second, but in this time the voltage can increase from 110 to 1,000 volts or even higher.
Voltage surges can disrupt or even damage your computer equipment

7. Lightening Strike
Enormous amount of electricity involved in a storm, a strike near your PC--near meaning within several miles--can induce currents in metal objects.
Any wire that comes in from the outside and attaches to your PC can become a conduit for a pulse of destructive energy such as a telephone line or power cord.

8. Brownout and Blackout
Brownout - when a brownout occurs, the voltage drops from its normal level to a lower voltage and then returns; in some ways, it's like the opposite of a surge.
Blackout - A blackout, of course, is when the power totally fails.

9. Basic Electricity Link to Electrical Basics
This is an excellent site to link students to the basics of electricity. This may be to in depth for the IT Essentials Class. I did not add this information to the student worksheet. I added this page in case instructors would like to teach additional information about electricity related to the power supply.

10. Parts of the Power Supply Internal Power Parts of the Power Supply
Power supplies generate high voltages internally and can be dangerous.
Unless you have been specifically trained to work inside power supplies, you should not open one.

11. Power Supply Specs Input Voltages and Tolerances
Input Voltage Range – acceptable range of input – 85v-135v AC or 170v-270v AC
Output Rating (Watts) – output of power measured in watts
Link to
Calculating Watts

12. Power Switch
Power switches to the power supply have changed over time.
Older PC/XT form factor– computer was turned on by a switch in the back of the computer.
AT form factor – added a remote switch on the front of the computer connected to the power supply in the back.
ATX/NLX form factor – uses an electric switch connected to the motherboard that uses a feature called Soft_Power to turn on the computer.

13. Voltage Selector Switch
Normally dual voltage selector to be set at either 110/220v.
110 – Normal voltage setting
220 – For settings out of the U.S.
If a 110v is set to 220v damage can occur.

14. Motherboard Connector
Most important connection.
Supplies power to other devices through the motherboard.
Wires are made of copper.
ATX 20 pin
Older P8 & P9
Or P1 & P2

15. Motherboard Connectors
Colors are used to depict the about of voltage each wire may carry. (Most but not all manufactures follow it.)
The P8 and P9 must be inserted correctly or the motherboard could be ruined. (Black to Black your motherboards back, red to red your motherboards dead.)
Power supply motherboard connectors are based on the form factor of the motherboard.

16. Motherboard Connector VoltagesP8 P9
ATX Style

17. Drive Connectors
The power supply provides power to internal hard disk, floppy disk, CD/DVD and other drives directly, through four-wire connectors that are designed to attach to the rear of each drive
The number of connectors that come with a system may vary.
There is a specific smaller floppy drive connector.
Multiple larger four pin connectors may be used on hard drives, CD-ROMS, and DVD.
A Y-Connector may add flexibility to drive connectors but is not recommended.

18. Drive connectors
Hard drive
CD-ROM
Floppy drive

19. Power Supply Fan Primary cooling source for the entire PC.
Power supply fans may be made of different components and move different levels of air.
The fan is usually the first piece of the power supply to fail because of dirt in the air.
Most computers use additional auxiliary fans to help cool the entire PC.

20. Additional Hardware Help
Sysopt.com
tomshardware.com
cnet.com