Download Power Supplies - ITCK

ITCK
Mohibullah Utmankhil
Information Technology Center of Kabul University
Kabul University
[email protected]
Date: 20 May 2015
By the end of this chapter, you should be able to:
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Discuss the major internal components of a PC.
Explain the basics of electricity
Describe the details about powering the PC
Install and maintain power supplies
Understand power supply troubleshooting and fire safety
Inside the System Unit
Now that you’ve seen the devices that connect to the PC, it’s time to open up the system unit to
inspect the major internal components of a typical PC. A single PC is composed of thousands of
discrete components. Although no one can name every tiny bit of electronics in a PC, a good
technician should be able to name the major internal components that make up the typical PC.
Case: The system unit’s case is both the internal framework of the PC and the external skin that
protects the internal components from the environment. Cases come in an amazing variety of
styles, sizes, and colors.
The front of the case holds the buttons for turning the system on and off, lights to tell you the
status of the system, and doors for accessing removable media drives such as digital versatile
disc (DVD) drives, also provides USB, FireWire, and audio connections in the front for easy
access if you want to use a device that needs these Connections.
Continue…
The back of the case holds the vast majority of the system unit connections. You
will also notice the power supply almost always at the top of the case distinguished
by its cooling fan and power plug.
Note that one area of the back, the input/output (I/O) area, holds all of the
onboard connections, while another area in the back contains slots for cards.
Similarly, the case uses slots to enable access to the external connectors on cards
installed in the system unit.
Opening a case is always...interesting. There’s no standard way to open a case.
In general, you detach the sides of a case by removing a few screws in the back of
the system unit, Use common sense and you won’t have too many problems. Just
don’t lose track of your screws or where each one was inserted!
Continue…
Take a look at the front of your PC and you’ll see all kinds of connectors, from power
and reset buttons to USB and audio ports. Front connections are most commonly
used for temporary devices, such as headphones. If you have a device you don’t
intend to remove very often, you should install it in one of the back connections.
Once you’ve opened the case, take a look inside. You’ll see metal framework, all
kinds of cables, and a number of devices. As you inspect the devices, you may gently
push cables to the side to get a better view. Don’t forget to wear an anti-static wrist
strap (attaching it to any handy metal part of the case) or touch the metal case
occasionally to prevent ESD.
CPU: The central processing unit (CPU), also called the microprocessor, performs all
of the calculations that take place inside a PC. CPUs come in a variety of shapes and
sizes. Modern CPUs generate a lot of heat and thus require a cooling fan and heat
sink assembly to avoid overheating. A heat sink is a big slab of copper or aluminum
that helps draw heat away from the processor. The fan then blows the heat out into
the case. You can usually remove this cooling device if you need to replace it,
although some CPU manufacturers have sold CPUs with a fan permanently attached.
Continue…
CPUs have a make and model, just like automobiles do. When talking about a particular car, for
example, most people speak in terms of a Ford Taurus or a Toyota Camry. When they talk about
CPUs, people say Intel Core i7 or AMD Phenom. Over the years, there have been only a few
major CPU manufacturers. Just as there are only a few major auto manufacturers. The two
most common makes of CPUs used in PCs are AMD and Intel.
Although only a few manufacturers of CPUs have existed, those manufacturers have made
hundreds of models of CPUs. Some of the more common models made over the past few years
have names such as Core 2 Duo, Core i5, Core i7, Phenom II, and AMD-FX.
Finally, CPUs come in a variety of packages. The package defines how the CPU looks physically
and how it connects to the computer. Intel CPUs currently use a package type called land grid
array (LGA), and AMD likes pin grid array (PGA). Every CPU package type has a number of
versions, and each package type is designed to fit into a particular connection called a socket.
Sockets have such names as Socket AM3 or Socket B.
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RAM: Random access memory (RAM) stores programs and data currently
being used by the CPU. The maximum amount of programs and data that a
piece of RAM can store is measured in units called bytes.
Modern PCs have many millions, even billions, of bytes of RAM, so RAM is
measured in units called megabytes (MB) or gigabytes (GB). An average PC
will have from 1 to 4 GB of RAM, although PCs may have more or less.
Each piece of RAM is called a stick. One common type of stick found in today’s
PC is called a dual inline memory module (DIMM).
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Motherboard: You can compare a motherboard to the chassis of an
automobile. In a car, everything connects to the chassis either directly or
indirectly. In a PC, everything connects to the motherboard either directly or
indirectly. A motherboard is a thin, flat piece of circuit board, usually green or
gold, and often slightly larger than a typical piece of notebook paper
A motherboard contains a number of special sockets that accept various PC
components. The CPU and RAM, for example, plug directly into the
motherboard. Other devices, such as floppy drives, hard drives, and CD and
DVD drives, connect to the motherboard sockets through short cables.
Motherboards also provide onboard connectors for external devices such as
mice, printers, joysticks, and keyboards.
Continue…
Hard Drive: A hard drive stores programs and data that are not currently
being used by the CPU. Although RAM storage is measured in megabytes and
gigabytes, a PC’s hard drive stores much more data than a typical PC’s RAM—
hundreds of gigabytes to terabytes. A terabyte is 1000 gigabytes.
An average PC has one hard drive, although most PCs accept more. Special
PCs that need to store large amounts of data, such as a large corporation’s
main file-storage computer, can contain many hard drives—8 to 16 drives in
some cases.
The two most common types of hard drives seen in today’s PCs are the older
Parallel Advanced Technology Attachment (PATA) and the more modern Serial
Advanced Technology Attachment (SATA).
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Optical Drives: Optical drives enable a computer to read one or more
types of optical discs, such as CD, DVD, or Blu-ray Disc. CDs store around
700 MB and come in three varieties: CD-ROM (read only memory: you
can’t change the data on them), CD-R (recordable: you can change the
data once), and CDRW (rewritable: you can change the data on them over
and over). DVDs store much more data the smallest capacity DVDs store
around 4 GB and come in even more.
varieties: DVD-ROM, DVD+R, DVD-R, DVD+RW, and DVD-RW, just to name
the more famous ones.
Blu-ray Discs are popular for high-definition movies, but there are also
Blu-ray Discs for storing data with capacities starting at 25 GB.
All of these optical discs require an optical drive that knows how to read
them. If you want to do anything with a CD-RW disc, for example, you
need a CD-RW drive. If you want to use a DVD+R disc, you need a DVD+R
drive. Luckily, most optical drives support many different types of discs,
and some support every common type of optical disc available.
Power Supplies
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Powering the PC requires a single box.
The power supply takes electricity from the wall socket and transforms it into
electricity to run the motherboard and other internal components.
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 so that a particular device will function is
expressed as how much wattage (watts or W) that device needs.
The Wires of all sorts whether copper, gold, or platinum have a slight resistance to
the flow of electrons.
A particular thickness of wire only handles so much electricity at a time.
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Electricity comes in two flavors:
1. Direct Current (DC)
2. Alternating Current (AC),
Direct Current (DC) in which the electrons flow in one direction around a
continuous circuit.
Alternating current (AC), in which the flow of electrons alternates direction
back and forth in a circuit .
Your PC uses DC voltage and the power supply in a computer converts highvoltage AC power from the wall socket to low-voltage DC.
Every PC power supply must have standard AC power from the power
company.
Power supplies with voltage selection switches are referred to as fixed-input.
Power supplies that you do not have to manually switch for different voltages
are known as auto-switching.
The power supply connects to the power cord via a standard IEC-320
connector.
Continue…
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Two essential devices handle spikes and sags in the AC:
1. Surge suppressors.
2. Uninterruptible power supplies (UPS).
Surges or spikes are far more dangerous than sags.
Surges are controlled by Surge Suppressors.
A strong sag only shuts off or reboots your PC a strong surge destroys components.
An uninterruptible power supply (UPS) protects your computer in the event of a
power sag or power outage.
There are two main types of UPS:
1. Online, where devices are constantly powered through the UPS’s Battery.
2. Standby, where devices connected to the UPS receive battery power only when
the AC sags below ~80–90 V.
line-interactive, which is similar to a standby UPS but has special circuitry to handle
moderate AC sags and surges without the need to switch to battery power.
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Power supplies come in a large number of shapes and sizes, but the most common
size by far is the standard 150 mm × 140 mm × 86 mm.
The PC uses the 12.0-V current to power motors on devices such as hard drives
and optical drives, and it uses the 5.0-V and 3.3-V current for support of onboard
electronics.
Modern motherboards use a 20- or 24-pin P1 power connector.
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The typical PC power supply has up to three types of connectors that plug into peripherals:
1. Molex
2. Mini
3. SATA
SATA
Mini
Molex
Installing and Maintaining Power Supplies
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The typical power supply connects to the PC with four standard computer screws,
mounted in the back of the case.
ATX power supply never turns off. As long as that power supply stays connected to a
power outlet, the power supply will continue to supply 5 V to the motherboard.
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Heat and computers are not the best friends  .
Computers, being electrical devices, generate heat as they operate, and too
much heat can seriously damage a computer’s internal components.
The power supply fan provides the basic cooling for the PC provides a
constant flow of outside air throughout the interior of the computer case.
If you ever turn on a computer and it boots just fine but you notice that it
seems unusually quiet, check to see if the power supply fan has died.
Some power supplies come with a built-in sensor to help regulate the
airflow. If the system gets too hot, the power supply fan spins faster.
In an effort to ensure proper cooling, many techs put several high speed
fans into a case, making the PC sound like a jet engine.
Troubleshooting Power Supplies
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Power supplies fail in two ways:
1. Sudden death.
2. Slowly over time.
When they die suddenly, the computer will not start and the fan in the power
supply will not turn.
• Verify that electricity is getting to the power supply before you do
anything.
• Power supplies will not start unless they’re connected to a motherboard.
• First, try an ATX tester. Many companies make these devices.
• Look for one that supports both 20- and 24-pin motherboard connectors as
well as all of the other connectors on your motherboard.
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The majority of PC problems occur when power supplies die slowly over time.
Clues you may hear from users:
• “Whenever I start my computer in the morning, it starts to boot, and then
locks up. If I press CTRL-ALT-DEL two or three times, it will boot up fine.
• “Sometimes when I start my PC, I get an error code. If I reboot, it goes away.
Sometimes I get different errors”.
• “My computer will run fine for an hour or so. Then it locks up, sometimes
once or twice an hour.”
That’s the clue for replacing the power supply.
Power supplies break in computers more often than any other part of the PC.