Computer Maintenance

1. Computer Maintenance Power Quality and Protection

2. External Power Problems • External power which comes from a home or office wall outlet, is the power everyone tends to take for granted; as long as it’s fine. • You may be surprised by the number of problems external power can have: • Line noise • Spikes • Surges • Brownouts • Blackouts

3. External Power Problems (Continued) • Most external power problems go unnoticed, because they are usually small enough that the computer’s power supply can deal with them (except for the blackout). • These problems however, can lead to reliability problems in your computer. • When you plug your computer directly into the wall socket, you are subjecting your computer to several problems. • Some of these problems your computer can handle, but over time, even unnoticed problems can take their toll and result in major damage

4. External Power Problems (Continued) • You should know the kinds of problems that the PC can experience from external power. These problems are: • Line noise: • Consists of small variations in the voltage of the power line. • A small amount of noise is normal. • If you have your PC plugged into its own circuit (unshared line), you should have little trouble from line noise. • If your computer shares an extension cord with an appliance (i.e., an air conditioner), line noise will soon cause some major problems. • The power-regulating circuits in your power supply burn out, and any line noise passes through to the motherboard or disk drive.

5. External Power Problems (Continued) • You should know the kinds of problems that the PC can experience from external power. These problems are: (Continued) • Power surges: • A power spike or over-voltage happens when disturbances like distant lightning strikes, or other anomalies in the electrical supply grid, create a voltage spike that travels down the line and to your wall plugs. • The surge lasts for only a few thousandths of a second, but will cause the voltage to increase to 1,000 volts or higher. • High voltage spikes degrade the power supply. Multiple surges over time can destroy it.

6. External Power Problems (Continued) • You should know the kinds of problems that the PC can experience from external power. These problems are: (Continued) • Brownouts: • Also known as under-voltage, is the opposite of a power surge and happens when a sudden dip occurs in the power line voltage. • It doesn’t last too long, but it can. Usually, the power level drops below normal levels for a time and then returns to normal. • They are extremely common during periods of heavy load on the electrical system (hot afternoons/cold mornings). • The reduced voltage level causes many devices to run slower than normal or malfunction in other ways.

7. External Power Problems (Continued) • You should know the kinds of problems that the PC can experience from external power. These problems are: (Continued) • Blackouts: • Occur when the power fails completely. • Problems caused are usually more frustrating than damaging. • NOTE: The fluctuation of power surrounding a blackout can, however, harm your system. • If you are in the middle of something that is not saved, or defragging a hard drive when a blackout occurs you will certainly have problems. • More often the damage occurs when the power returns suddenly, usually in the form of a huge spike.

8. External Power Problems (Continued) • You should know the kinds of problems that the PC can experience from external power. These problems are: (Continued) • Lightning strikes: • This spike delivers a million volts or more if it were to hit a home or office directly. • A strike even in your vicinity can result in a very high voltage spike. • A lightning strike has been known to completely destroy or melt down every thing plugged in: computers, copiers, fax machines, telephones, and more.

9. Protecting Against Power Problems • Several levels of protection exist to protect your computer from these external power problems. • Two types of damage can be done to the PC by electrical forces: • Catastrophic: • When the device is destroyed all at once in a single event. • Degradation: • When a device is damaged over a period of instances and begins to fail or has intermittent problems.

10. Protecting Against Power Problems (Surge Suppressor) • Most users plug their computers into a power strip or surge suppressor. • The primary component of a surge suppressor is a Metal Oxide Varistor (MOV). • The MOV protects the computer by taking the hit from voltage spikes. • The problem with MOV is that one big spike or an accumulation of small surges over time can knock it out. • Some surge suppressors have a light to indicate that the MOV is still all right.

11. Protecting Against Power Problems (Surge Suppressor) • A surge suppressor reduces power problems by absorbing spikes and surges and by smoothing out line noise (called line conditioning) • Not all surge suppressors include line conditioning. • Consider two main features when choosing a surge suppressor: • Clamping voltage: • The voltage at which the suppressor begins to protect the computer. • Clamping speed: • The time lapse before the protection begins, or how much time elapses between detection and protection.

12. Protecting Against Power Problems (Surge Suppressor) • Other things to look for: • Energy absorption: • Surge suppressors are rated in Joules, which measures their capability to absorb energy • The higher the rating, the better the protection: • 200 Joules is basic protection • 400 Joules is good protection • 600 Joules is superior protection • Line conditioning: • Line conditioning capability of surge suppressors are measured in decibels. • The more decibels of noise reduction, the better the line conditioning.

13. Protecting Against Power Problems (Surge Suppressor) • Other things to look for: (Continued) • Protection indicators: • An LED indicates you are protected • If the LED is out, get a new suppressor • Levels of protection: • Surge suppressors have three levels of protection that indicate the maximum number of watts the suppressor allows to pass through to anything plugged into it. The standard ratings are: • 500 (Good) • 400 (Better) • 330 (Best)

14. Protecting Against Power Problems (Surge Suppressor) • Line conditioners filter the power stream to eliminate line noise. • Because they are usually expensive, few PC users use a true line conditioner. • They prefer to purchase this capability in other devices, such as a surge suppressor. • In the event of an electrical storm or lightning strike, power can surge up the telephone lines as well as the power lines. • When installing a surge protector, be sure it has phone line protection.

15. Protecting Against Power Problems (UPS) • An uninterruptible power supply (UPS) provides a constant (uninterruptible) power stream to the computer. • Under normal conditions, it’s a surge protector that can also handle brownout conditions. • When the power drops below a certain level or is disrupted completely, the UPS kicks in and provides power for a certain number of minutes, or even hours in some cases.

16. Protecting Against Power Problems (UPS) (cont.) • All UPS units have two sets of circuits: • One side is the AC circuit that, in effect, is a surge suppressor. • The other side is the battery and DC to AC conversion. • The batteries store a DC charge that must be converted to AC (because that’s what the PC expects).

17. Protecting Against Power Problems (UPS) (cont.) • Two types of UPS units are available: • Standby UPS: • Operates normally from its AC side. • When the power drops, it switches over to its battery backup side. • In-line UPS: • Operates normally from its DC or battery backup side. • The AC side is only used in the event of a problem with the battery-powered circuits. • UPS units are often confused with a standby power supply (SPS), or battery backup, which only supplies power when none is available and has no power conditioning abilities. • Never plug a laser printer or monitor into a conventional PC UPS. These devices are not critical to the operation of the PC and draw tremendous amounts of power at startup.

18. Summary Slide • Introduction to external power problems • Reliability problems • Damage problems • Line noise • Power surges • Brownouts • Blackouts • Lightning strikes • Protecting Against Power Problems • Catastrophic damage • Degradation damage

19. Summary Slide (Continued) • Protecting Against Power Problems (Surge Suppressor) • Metal Oxide Varistor (MOV) • Line conditioning • Clamping voltage • Clamping speed • Energy absorption • Protection indicators • Levels of protection • Phone line protection

20. Summary Slide (Continued) • Protecting Against Power Problems (UPS) • AC circuit • Battery and DC to AC conversion • Standby UPS • In-line UPS • Standby Power Supply (SPS)