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8/14/2019 Proftech_Module 3 revised 6 06

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2Version 3.1

Before beginning any assembly process, it is a

good idea to review safety procedures.

Keep the work area free of clutter and keep it clean.

Keep food and drinks out of the work area.

A computer monitor may store up to 25,000 volts, so avoid opening

one unless trained to do so.

Remove all jewelry and watches.

Make sure the power is off and the power plug has been removed

when working inside the computer.

Never look into a laser beam. Lasers are found in computer related

equipment.

Make sure that a fire extinguisher and first aid kit is available.

Cover sharp edges with tape when working inside the computer

case.


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Basic Safety Procedures

Use an antistatic mat and grounding wrist strap. Use antistatic bags to store and move computer components.

Do not remove or install components while the computer ison.

Ground often to prevent static charges from building up by

touching a piece of bare metal on the chassis or powersupply.

Work on a bare floor because carpets can build up staticcharges.

Hold cards by the edges to avoid touching chips or the edgeconnectors on the expansion cards.


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Basic Safety Procedures

Do not touch chips or expansion boards with a magnetizedscrewdriver.

Turn off the computer before moving it. This is to protect thehard drive, which is always spinning when the computer isturned on.

Do not place a circuit board of any kind onto a conductivesurface.

Do not use a pencil or metal tipped instrument to change DIPswitches or to touch components. The graphite in the pencil isconductive and could easily cause damage.

Do not allow anyone who is not properly grounded to touch orhand off computer components. This is true even whenworking with a lab partner. When passing components,always touch hands first to neutralize any charges.


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ESD Precautions

Electrostatic discharge (ESD) is more commonly referred toas static electricity.

ESD is probably the greatest enemy when a user unwraps

newly purchased computer parts and components while

preparing to assemble the computer.

The best way to protect against ESD is to use an anti-static

mat, a grounding wrist strap, and anti-static bags.


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ESD Precautions

Always review the ESD precautions before beginning theassembly process.

Keep all computer parts in anti-static bags.

Keep the humidity between 20 - 30 percent.

Use grounded mats on workbenches.

Use grounded floor mats in work areas.

Use wrist straps when working on computer parts, except

when working on monitors or power supplies. Periodically touch unpainted grounded metal parts of the

computer to lower the static energy of the body.


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Computer Cases

There are three basic types of computer cases: Desktop

Tower

Mini-tower

Mid-tower

Full tower

Portable

Whether buying a tower or desktop, it is recommended that itconforms to the ATX standard and has at least a 250-wattpower supply (300 watts is ideal.)

The desktop case is considered the most difficult to upgrade.


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Desktop Computers

The desktop design is one of the more familiar case styles.Desktop units are designed to sit horizontally on the desktop.

The two important considerations in choosing a desktop case

style for a computer are:

Available desktop space

Form factor

The newest form factor,

and the one most often

encountered, is the ATX.


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Tower Computers

Tower cases are usually designed to sit vertically on the floorbeneath a desk.

Tower cases come in three sizes:

Mini towers

Mid towers

Full-size towers


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Power Supplies

The power supply is one of the most important parts thatneeds to be understood. The power supply unit provides

electrical power for every component inside the system unit.

The power supply plays the critical role of converting

commercial electrical power (AC), into DC required by thecomponents of the computer.

There are two basic types of power supplies:

AT power supplies Designed to support AT-compatiblemotherboards.

ATX power supplies Designed according to newer ATX

design specifications to support the ATX motherboard.


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Power Supplies

There are two major distinctions between the legacy AT andthe new ATX power supplies.

The AT power supply has two 6-pin (12 pins) motherboard

power connectors (P8/P9)

The ATX power supplies use a single 20-pin power

connector (P1).

In the ATX-compatible power supply, the cooling fan pulls

air through the case from the front and exhausts it out therear of the power supply unit.

The AT design pulls air in through the rear of the power

supply unit and blows it directly on the AT motherboard.


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Power Supplies

The power supply produces four (five in the ATX) differentlevels of well-regulated DC voltage for use by the system

components.

These are +5V, -5V, +12V, and -12V.

In ATX power supplies, the +3.3V level is also produced and

is used by the second-generation Intel Pentium processors.


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Power Supplies

Ground -- Used to complete circuits with the

other voltagesBlack0 volts

Most newer CPUs, some types of memory,

and AGP video cardsOrange+ 3.3 volts

ISA bus cards and early PROMSWhite- 5 volts

Motherboard, Baby AT and earlier CPUs, and

many motherboard componentsRed+ 5 volts

Some types of serial port circuits and earlyprogrammable read only memory (PROM)

Blue- 12 volts

Disk drive motors, fans, cooling devices, and

the systems bus slotsYellow+ 12 volts

UseWire ColorVoltage

ATX


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Motherboard Location Map

A motherboard location map

shows where the major

components and hardware is

located on the motherboard.

A motherboard map can be

found in the documentation

that comes with the

motherboard.


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Configuring the Motherboard

Configuring the motherboard typically means the following:

Installing the CPU

Installing the heat sink and fan

Installing RAM

Connecting the power supply cables to the motherboard

power connectors and connecting miscellaneous

connectors to the correct switches and status lights on thefront case panel.

Setting the system BIOS (Basic Input Output System)


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Configuring the Connectors

For the disk controllers, always remember that a coloredstripe on the data cable is pin-1.

Most modern connectors are "keyed" by a missing pin or a

blocked connector, so they cannot be fitted the wrong way.

Usually, the colored wire(s) in a power cable are positive and

the white or black wire(s) are ground or negative.


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CPU Interfaces

There are two main types of CPU interfaces.

Socket type (e.g., socket 7) - Socket 7 has been the

standard interface, although the newer systems are now

using different sockets. It is the only interface used by at

least one generation of Intel Pentium processors (Pentium

I) as well as AMD and Cyrix chips.

Slot type (e.g., slot 1.) - Slot type interfaces use a slot

similar to expansion cards. Slot 1 is the Single EdgeContact (SEC) interface used only by the Intel Pentium II

processor family.


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RAM

The two types of memory modules used on most PCs are: Dual Inline Memory Module (DIMM)

Single Inline Memory Module (SIMM)


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RAM

Dual Inline Memory Module (DIMM) 168-pin

DIMM cards are inserted straight into the slots

When DIMM sizes are mixed on the motherboard, it isimportant to remember to put the DIMM with the largest

memory size in the first bank.


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RAM

Rambus Inline Memory Module (RIMM) 184 pins

RIMM modules use only the direct Rambus memory chips(RDRAM)

RDRAM is characterized by its high bus speed.

RIMMs require that if you do not fill all RIMM slots withRDRAM memory, you must keep the empty slots filled withtermination boards


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Connecting the Power Supply

The power supply converts the alternation current (AC) linefrom your home to the direct current (DC) needed by the

personal computer.

This process will vary depending on the type of motherboard

that is being installed (AT or ATX).

Sometimes it is helpful to delay attaching the power connector

to the board until all the components

have been installed that need to go

on the motherboard.

This allows for more working

space inside the case.


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Connecting the Power Supply

WARNING:Do not open the power supply it contains acapacitors which can hold Electricity (WHICH CAN KILL)

even if the computer is power off for a week, if not

longer. If you do open it WHICH IS NOT

RECOMMENDED, take all precautions and ensure you

work with one arm behind your back to direct the

electricity away from the heart. Also ensure that you

have no jewelry on (such as a watch or rings). Howeveragain THIS IS NOT RECOMMENDED and still cannot

protect you 100% and is still potentially dangerous.


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AT Power Supply

AT power supplies are considered legacy AT motherboards have a 12 pin connector and the AT power

supply has two 6 pin connectors (P8 and P9).

Plug the P8 and P9 wire lead connectors in the 12-pin power

connector.

Make sure the black wires are in the middle, right next to each

other or the motherboard could be damaged.


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ATX Power Supply

ATX is currently the most common type of power supply.

ATX motherboards have a single 20 pin connector (P1).

The connector is keyed for easy installation.


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Connecting Floppy Drives

The floppy drive exchanges data with the motherboarddevices, including the microprocessor, via a 34-pin flat ribbon

(data) cable

Usually, a red stripe on the edge of the cable identifies pin-1.

Lining the red-stripe edge with pin-1 of the drive connector or

drive controller interface assures a correct alignment.

If the cable is incorrectly oriented it becomes immediately

apparent on power up by the fact that the floppy drive LEDlight comes on immediately and stays on.


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Connecting Floppy Drives

Current system BIOS versions can support up to twofloppy drives on one controller via a daisy chain cable

arrangement. Cable pin-outs 10 through 16 are cross-

wired between the middle drive connector and end drive

connector, producing a twist that reverses the Drive

Select (DS) configuration of the drive plugged into the

end connector of the ribbon cable. This feature, called

cable select, automatically configures the drive on themiddle connector as Drive B and the drive on the end

connector as Drive A. The twist is beside the Drive A

connector.


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Installing a Hard Drive or CD-ROM

Attaching the hard drive and CD-ROM are basically similar.

First, the jumper settings should be properly set.

The designation of a hard drive or CD-ROM drive as either

master or slave is generally determined by the jumper

configuration, not by the order in which the drive is daisy-

chained to the other drive.

The hard drive that is used to boot the computer should be set

as the primary master

The only exception is if the drive is jumpered (set to) "cable

select" and both the system and ribbon cable support cable

select.


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Connecting a Hard Drive or CD-ROM

Hard drives and CD-ROM drives communicate with the rest of

the system using ribbon cables.

Ribbon cables are widely used to connect peripherals such as

floppy drives and hard drives internally.

IDE cable ribbon cables used for hard drives and CD-ROM

drives typically have 40 pins and can connect two devices to

each cable.


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Power On Self Test

Whenever a computer starts up, a series of tests are automatically

performed to check the primary components in the system, such as

the CPU, ROM, memory, and motherboard support circuitry.

The routine that carries out this function is referred to as the POST.

POST is a hardware diagnostics routine that is built into the system

BIOS.

The basic function of the POST routine is to make sure that all the

hardware the system needs for startup is there and that everything

is functioning properly before the boot process begins.


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Power On Self Test

POST also provides some basic troubleshooting to determine

what devices have failed or have problems initializing during

this pre-startup hardware check.

The POST routine provides error or warning messages

whenever it encounters a faulty component.

Post error codes take the form of a series of beeps that

identify a faulty hardware component.


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Power On Self Test

If the Post advances up to the point where video can be displayed,

the error codes are displayed on the monitor.

Mouse86xx

Hard drive17xx

Floppy drive6xx

Color monitor5xx

Keyboard3xx

Main memory2xx

CMOS, options or time not set16x

System board or BIOS1xx

Possible ProblemError Code/Range

proftech_module 3 revised 6 06

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