CPU Case and Power Supply

PREPARED BY: KRISANDRA N. GAYLON

Types of PC Case

1. Desktop Case

2. Tower Case

3. Shuttle Case

Computer Case

• A computer case (also known as a computer chassis, cabinet, box, tower, enclosure, housing, system unit or simply case) is the enclosure that contains most of the components of a computer.

Why do we need a computer case?• Most people overlook the computer case as just a box, but it does provide the

below important features.

Structure - The case is what holds everything together in a compact and organized fashion.

Protection - Without the case, each of the sensitive components within the computer would be vulnerable to dirt, foreign objects, kids, animals, as well as electrical interference (EMI / RFI).

Cooling - The case helps keep the air properly flowing over all components, which keeps everything cool and running properly.

Noise - Many computers and components have fans that generate noise. Having those components within a confined case reduces the overall noise.

Aesthetics - Although some may disagree, most people would rather look at the case instead of all the circuit boards, wires, and all the components of a computer.

Front Panel & Cooling System

Power Supply

• is a device that supplies electric power to an electrical load.

• Is used to convert AC (Alternating Current) to DC (Direct Current).

• A power supply may be implemented as a discrete, stand-alone device or as an integral device that is hardwired to its load. Examples of the latter case include the low voltage DC power supplies that are part of desktop computers and consumer electronics devices.

Power Supply Connectors• ATX –Advanced Technology Extended Connector

• AT-Advanced Technology Connector

• Mini connector use in floppy disk drive

• Molex connector use in hard disk drive, cd rom, dvd rom.

Power Supply Failures1. Sags – power sag (or low line voltage) is a decrease in line voltage of at least

10% of the average line voltage for half a cycle or longer. The power sag is often caused by large inductive equipment, e.g. photocopy, bank of fluorescent lights. Sags can be caused by external factors as well, such as large power draining equipment used in other buildings. Sags can be particularly detrimental to electronic equipment because of the malfunctions caused by the sudden decrease of available voltage to the power supply. Relays and solenoids can chatter generating spikes (see above). Complete failure rarely occurs, however equipment lockup or lockout can occur requiring a resetting process. Often  equipment continues to operate, with the user, unaware of any problems that may have occurred.

2. Surge - A power surge is the opposite of a sag and is often referred to as "High Line Voltage". A surge is defined as an increase in line voltage above 253 volts (on a 230V Line) for a half cycle or longer. Like the sag, the power surge is often caused by large inductive loads being applied on the same line. Power surges can cause some of the most dangerous situations, and their resulting damage is most difficult to repair.

3. Spike - is a surge of energy superimposed on the AC line, generally of short duration. Spikes can potentially have the most serious effects on electronic equipment due to their high energy content, and the Integrated Circuits inability to absorb the energy.

4. Brownout – is an intentional drop in voltage in an electrical power supply.

• Intentional – are used for load reduction in an emergency.• Unintentional -

5. Blackouts - A power failure or blackout is a zero-voltage condition that lasts for more than two cycles. It may be caused by tripping a circuit breaker, power distribution failure or utility power failure. A blackout can cause data loss or corruption and equipment damage.

Power Supply Protector

• Surge Suppressor

• AVR (Automatic Voltage Regulator)

• UPS (Uninterruptable Power Supply)

Things to consider when replacing power supply

1. Physical size

2. Wattage

3. Connectors