Video Display and Audio SystemsVideo Display and Audio SystemsBasic PC Maintenance, Upgrade and RepairBasic PC Maintenance, Upgrade and Repair

Mods 1 & 2Mods 1 & 2

Display ConceptsDisplay Concepts

There are a number of features common to all monitors.There are a number of features common to all monitors. These features such as dot pitch and size, greatly affect These features such as dot pitch and size, greatly affect

the quality of the picture, as well as the price the user the quality of the picture, as well as the price the user pays for it.pays for it.

Monitor SizeMonitor Size – Standard sizes are 14”, 15”, 17”, 19”, – Standard sizes are 14”, 15”, 17”, 19”, and 21”. It is measured from one corner to the opposite and 21”. It is measured from one corner to the opposite corner of the monitor.corner of the monitor.

Dot PitchDot Pitch – the distance measured in millimeters – the distance measured in millimeters between two color dots on the screen. It directly affects between two color dots on the screen. It directly affects the quality of the image displayed.the quality of the image displayed.

Generally, the smaller the dot pitch, the sharper the Generally, the smaller the dot pitch, the sharper the image displayed.image displayed.

Common dot pitch is from 0.28 mm to 0.25 mm. It Common dot pitch is from 0.28 mm to 0.25 mm. It cannot be adjusted.cannot be adjusted.

Display ConceptsDisplay Concepts Color Display ValuesColor Display Values – The color display quality is – The color display quality is

determined by the number of bits used to represent the determined by the number of bits used to represent the individual colors of red, green, and blue.individual colors of red, green, and blue.

This can also determine the possible number of color This can also determine the possible number of color shades.shades.– A byte contains 8 bits.A byte contains 8 bits.– There are 256 combinations of 1’s and 0’s available with 8 bits.There are 256 combinations of 1’s and 0’s available with 8 bits.– This means that an 8 bit color pattern can reproduce 256 This means that an 8 bit color pattern can reproduce 256

intensities of a specific color.intensities of a specific color.– By mixing the intensities of red blue and green, other colors By mixing the intensities of red blue and green, other colors

can be produced.can be produced.

Color Display Color Display ValueValue

Number of ColorsNumber of Colors

8 bit8 bit 256256

16 bit (True color)16 bit (True color) 65,53665,536

24 bit (True color)24 bit (True color) 16,000,00016,000,000

32 bit (True color)32 bit (True color) 4,000,000,0004,000,000,000

Display ConceptsDisplay Concepts

Display ResolutionDisplay Resolution – this term refers to the amount of – this term refers to the amount of detail a monitor is capable of displaying.detail a monitor is capable of displaying.

The term is also used by printers, digital cameras, etc.The term is also used by printers, digital cameras, etc. The higher the value, the better the detail and quality The higher the value, the better the detail and quality

of the picture.of the picture. Resolution is measured in Resolution is measured in pixelspixels. A pixel is the . A pixel is the

smallest unit of color in a screen display.smallest unit of color in a screen display.

ResolutionResolution AcronyAcronymm

DesignationDesignation Number of Number of PixelsPixels

640 x 480640 x 480 VGAVGA Video Graphics ArrayVideo Graphics Array 307,200307,200

800 x 600800 x 600 SVGASVGA Super VGASuper VGA 480,000480,000

1024 x 7681024 x 768 EGAEGA Extended Graphics Extended Graphics ArrayArray

786,432786,432

1280 x 10241280 x 1024 UVGAUVGA Ultra VGAUltra VGA 1,310,7201,310,720

Types of DisplaysTypes of Displays

There are a number of different types of display There are a number of different types of display systems for computers.systems for computers.

The two most common types are . . . .The two most common types are . . . .– CRTCRT – Cathode Ray Tube – Cathode Ray Tube– LCDLCD – Liquid Crystal Display – Liquid Crystal Display

Cathode Ray Tube – A picture tube in which a beam of Cathode Ray Tube – A picture tube in which a beam of electrons sweeps across a glass tube, exciting electrons sweeps across a glass tube, exciting phosphorus dots in the screen.phosphorus dots in the screen.

Liquid Crystal Display – A type of monitor that uses Liquid Crystal Display – A type of monitor that uses polarized light passing through liquid crystal to create polarized light passing through liquid crystal to create images on screen.images on screen.

CRT’sCRT’s A CRT has two ends, Cathode and AnodeA CRT has two ends, Cathode and Anode

CRT’sCRT’s The Anode has a positive voltage potential between The Anode has a positive voltage potential between

16,000 to 25,000V. 16,000 to 25,000V.

CRT’sCRT’s A filament connected to the cathode is heated and it A filament connected to the cathode is heated and it

emits electrons. These electrons form a cloud.emits electrons. These electrons form a cloud.

CRT’sCRT’s The electrons are attracted to the positive Anode, are The electrons are attracted to the positive Anode, are

accelerated and focused into a pencil beam.accelerated and focused into a pencil beam.

CRT’sCRT’s The accelerated electrons collide with the phosphor The accelerated electrons collide with the phosphor

coating on the Anode and emit light.coating on the Anode and emit light.

CRT’sCRT’s Horizontal and vertical deflection coils position the pencil Horizontal and vertical deflection coils position the pencil

beam in the desired location on the phosphor screenbeam in the desired location on the phosphor screen

CRT’sCRT’s The pencil beam is moved across the screen and down The pencil beam is moved across the screen and down

in precise increments.in precise increments. 525 horizontal lines are completed 60 times every 525 horizontal lines are completed 60 times every

second. The movement of the pencil beam uses the second. The movement of the pencil beam uses the terms trace, retrace and blanking.terms trace, retrace and blanking.– Trace is when the line of video is being produced.Trace is when the line of video is being produced.– Retrace is when the pencil beam is moved back to its Retrace is when the pencil beam is moved back to its

horizontal starting position.horizontal starting position.– Blanking is the blocking of the pencil beam during Blanking is the blocking of the pencil beam during

retrace so it is not seen on the screen.retrace so it is not seen on the screen. Color systems work similar, except there are three Color systems work similar, except there are three

electron pencil beams being directed at pixels electron pencil beams being directed at pixels containing red, blue and green phosphors.containing red, blue and green phosphors.

The intensity of each beam on the individual The intensity of each beam on the individual phosphors creates the specific color in that locationphosphors creates the specific color in that location

LCD’sLCD’s

The LCD operates off of two principles:The LCD operates off of two principles:– Polarized light.Polarized light.– The effect of an electrical voltage applied to a crystal structure.The effect of an electrical voltage applied to a crystal structure.

A typical light beam is composed of numerous waves of light.A typical light beam is composed of numerous waves of light. They travel in parallel, but at different wave angles.They travel in parallel, but at different wave angles. If a thin slot is cut in a material such as metal, only light waves If a thin slot is cut in a material such as metal, only light waves

with an angle matching the slot can pass through. This is with an angle matching the slot can pass through. This is polarized light. polarized light. http://www.olympusmicro.com/primer/lightandcolor/polarization.htmlhttp://www.olympusmicro.com/primer/lightandcolor/polarization.html

When an electrical voltage is applied to a crystal, the crystal When an electrical voltage is applied to a crystal, the crystal changes shape slightly or twists.changes shape slightly or twists.

The amount of twist is directly related to the amount of The amount of twist is directly related to the amount of voltage applied.voltage applied.

Light normally passes through the crystal in a straight line.Light normally passes through the crystal in a straight line. When a light is shined through a crystal and a voltage is When a light is shined through a crystal and a voltage is

applied to the crystal, the angle of the light wave changes as it applied to the crystal, the angle of the light wave changes as it passes through. passes through. http://electronics.howstuffworks.com/lcd3.htmhttp://electronics.howstuffworks.com/lcd3.htm

Sandwiched structure

LCD StructureLCD Structure

Passive and Active Matrix Passive and Active Matrix DisplaysDisplays

The two types of LCD displays are Passive and Active The two types of LCD displays are Passive and Active Matrix.Matrix.

Both use matrixes to determine how to select individual Both use matrixes to determine how to select individual pixelspixels

A passive matrix is a grid of semitransparent conductors A passive matrix is a grid of semitransparent conductors that run to each crystal. It is divided into columns and rows.that run to each crystal. It is divided into columns and rows.

Transistors running along the top and side of the display are Transistors running along the top and side of the display are activated in such a way as to activate a specific pixel activated in such a way as to activate a specific pixel (crystal) area. (crystal) area. http://electronics.howstuffworks.com/lcd7.htmhttp://electronics.howstuffworks.com/lcd7.htm

An active matrix display uses a matrix that has a transistor An active matrix display uses a matrix that has a transistor that activates at each pixel (crystal) location.that activates at each pixel (crystal) location.

The most common type is TFT (thin film transistor) LCD The most common type is TFT (thin film transistor) LCD displays. It offers a brighter image that responds more displays. It offers a brighter image that responds more quickly to changes.quickly to changes.

There are over a million transistors spread across a display, There are over a million transistors spread across a display, three for each pixel (red, green, blue). three for each pixel (red, green, blue).

Other LCD ConceptsOther LCD Concepts

Contrast Ratio – a numeric expression in the form of a Contrast Ratio – a numeric expression in the form of a ratio that that describes the amount of contrast ratio that that describes the amount of contrast between the darkest and the lightest pixel in the between the darkest and the lightest pixel in the image. image. – The higher the number the better.The higher the number the better.– Typical range is from 200:1 to 600:1Typical range is from 200:1 to 600:1– A contrast ration of over 500:1 is considered a high A contrast ration of over 500:1 is considered a high

quality display.quality display. Brightness – in an LCD display, this is produced by the Brightness – in an LCD display, this is produced by the

fluorescent backlight.fluorescent backlight.– It determines the maximum amount of brightness It determines the maximum amount of brightness

produced in the display.produced in the display.– Levels typically range from 200 cd/mLevels typically range from 200 cd/m22 (candela per (candela per

square meter) to 250 cd/msquare meter) to 250 cd/m22..

Other LCD ConceptsOther LCD Concepts

Viewing Angle – a measurement of the angle at which Viewing Angle – a measurement of the angle at which a person can adequately see an image on a display a person can adequately see an image on a display without it looking excessively distorted.without it looking excessively distorted.– Early LCD displays were quite limited in this area.Early LCD displays were quite limited in this area.– Today, most have a very acceptable viewing area.Today, most have a very acceptable viewing area.– Minimum around 150°, maximum around 170° (possibly Minimum around 150°, maximum around 170° (possibly

even more).even more). Pixel Pitch – similar to CRT dot pitch, it is the distance Pixel Pitch – similar to CRT dot pitch, it is the distance

between two same color pixels on the display area between two same color pixels on the display area (i.e. two red pixels, two blue pixels, etc.)(i.e. two red pixels, two blue pixels, etc.)– Each color pixel is composed of three Each color pixel is composed of three pelspels, one pel for , one pel for

each of the three colors that compose a pixel.each of the three colors that compose a pixel.– Pixel pitch is expressed in millimeters (mm) per inch.Pixel pitch is expressed in millimeters (mm) per inch.

Other LCD ConceptsOther LCD Concepts

Native Resolution – The resolution that matches the Native Resolution – The resolution that matches the pixel design of the displaypixel design of the display– Although an LCD display is capable of showing a number of Although an LCD display is capable of showing a number of

different resolutions, it will have the best images at its different resolutions, it will have the best images at its native resolution.native resolution.

Response Time – the amount of time it takes a TFT pixel Response Time – the amount of time it takes a TFT pixel to display after a signal is sent to the transistor to display after a signal is sent to the transistor controlling that pixel.controlling that pixel.– Measured in milliseconds (ms).Measured in milliseconds (ms).– A typical response is 15 to 40 ms.A typical response is 15 to 40 ms.– The lower the response time, the better quality of the unit, The lower the response time, the better quality of the unit,

especially with animation.especially with animation. Aspect Ratio – A ratio of a display areas height and Aspect Ratio – A ratio of a display areas height and

width.width.– Standard is 4:3Standard is 4:3– New HD TV uses 16:10New HD TV uses 16:10

Video Adapter CardsVideo Adapter Cards

Monitors can attach to computers in one of two ways:Monitors can attach to computers in one of two ways:– It can plug into a video adapter card inserted into an AGP It can plug into a video adapter card inserted into an AGP

or PCI slot on the motherboard.or PCI slot on the motherboard.– It can attach directly to the motherboard (that has It can attach directly to the motherboard (that has

integrated video components built in).integrated video components built in). The heart of the video adapter card is the special IC The heart of the video adapter card is the special IC

chip known as a digital to analog converter (DAC).chip known as a digital to analog converter (DAC).– It converts the computer’s digital video signal into an It converts the computer’s digital video signal into an

analog signal for the computer monitor.analog signal for the computer monitor.– The DAC can consist of one chip, or three, one for each The DAC can consist of one chip, or three, one for each

color.color. The video card also contains RAM, ROM, a video The video card also contains RAM, ROM, a video

processor, and BIOS.processor, and BIOS.

Video Adapter CardsVideo Adapter Cards

A VGA monitor uses a 15-pin connector to connect to A VGA monitor uses a 15-pin connector to connect to the video card.the video card.

Pin Description 1 Red Video 2 Green Video3 Blue Video4 Monitor ID Bit 2

(Ground)5 Ground 6 Red Return (Ground) 7 Green Return (Ground)8 Blue Return (Ground)9 Key (not used) 10 Sync Return (Ground) 11 Monitor ID Bit 0

(Ground)12 Monitor ID Bit 1 (Not

Used) 13 Horizontal Sync 14 Vertical Sync 15 Not Used

Video Adapter CardsVideo Adapter Cards Video cards are installed in PCI or AGP motherboard slotsVideo cards are installed in PCI or AGP motherboard slots AGP – Accelerated Graphics Port – is a slot used AGP – Accelerated Graphics Port – is a slot used

specifically for video cards and produces the highest specifically for video cards and produces the highest quality result of the two technologies.quality result of the two technologies.

AGP is designed with graphics as a priority, using a AGP is designed with graphics as a priority, using a computer’s memory to work more effectively with computer’s memory to work more effectively with graphics.graphics.

AGP also has a faster bus speed.AGP also has a faster bus speed.

Bus TypeBus Type Throughput Throughput MBpsMBps

Speed in MHzSpeed in MHz Width in Width in BitsBits

PCIPCI 127.2127.2 3333 3232

PCI 2.1PCI 2.1 508.6508.6 6666 6464

AGPAGP 254.3254.3 6666 3232

AGB x 2AGB x 2 508.6508.6 66 x 266 x 2 3232

AGP x 4AGP x 4 1,017.31,017.3 66 x 466 x 4 3232

AGP x 8AGP x 8 2,034.42,034.4 66 x 866 x 8 3232

Audio SystemsAudio Systems

Audio is the second half of the multimedia Audio is the second half of the multimedia experience.experience.

All PC’s come with a small internal speaker, but that All PC’s come with a small internal speaker, but that is not enough for most users.is not enough for most users.

Fancy sound cards, subwoofers, speakers and Fancy sound cards, subwoofers, speakers and microphones have become standard equipment on microphones have become standard equipment on many systems.many systems.

The human ear can detect sounds from approximately The human ear can detect sounds from approximately 20Hz to 20kHz. This is called the 20Hz to 20kHz. This is called the frequencyfrequency responseresponse rangerange of the human ear. Sound waves (vibrations) of the human ear. Sound waves (vibrations) above or below this range go undetected.above or below this range go undetected.

To convert analog sound to digital, a device called a To convert analog sound to digital, a device called a Analog to Digital Converter (ADC) is needed. The Analog to Digital Converter (ADC) is needed. The method used with this ADC is called method used with this ADC is called samplingsampling..

SamplingSampling

Sampling is the measurement of an analog signal at Sampling is the measurement of an analog signal at regular intervals. It is required to convert an analog signal regular intervals. It is required to convert an analog signal into a digital signal.into a digital signal.

The quality of the conversion is based on two main things:The quality of the conversion is based on two main things:– Sampling rateSampling rate– Number of bits used to represent the voltage level of the Number of bits used to represent the voltage level of the

signalsignal A high sampling rate gives a better representation of an A high sampling rate gives a better representation of an

analog signal shape, but also requires more memory and analog signal shape, but also requires more memory and hard disk space.hard disk space.

The number of bits available to represent analog voltage The number of bits available to represent analog voltage levels also can require more memory and hard disk space. levels also can require more memory and hard disk space.

Older systems used 8 bits, while systems today use 16 Older systems used 8 bits, while systems today use 16 bits.bits.

16 bits can much better represent the original sound.16 bits can much better represent the original sound.

8-bit vs. 16-bit8-bit vs. 16-bit

Sounds recorded with 8 bit technology is limited to 256 Sounds recorded with 8 bit technology is limited to 256 different voltage levels, or binary codes, required to different voltage levels, or binary codes, required to store a binary image of the sound wave sample.store a binary image of the sound wave sample.

16 bit sound cards can use 65,536 binary codes to 16 bit sound cards can use 65,536 binary codes to represent the analog voltage level during sampling. It is represent the analog voltage level during sampling. It is a more detailed representation of the sound wave a more detailed representation of the sound wave pattern.pattern.

Another name given to the number of bits used is Another name given to the number of bits used is ““resolutionresolution”. ”.

Audio DevicesAudio Devices

Microphone – a simple electronic device that converts sound Microphone – a simple electronic device that converts sound waves in to electrical energy. waves in to electrical energy. – It converts air vibrations that strike it into voltage levels that are It converts air vibrations that strike it into voltage levels that are

directly proportional to the strength and frequency of the directly proportional to the strength and frequency of the vibrationsvibrations

Speakers – a device that converts electrical energy to sound Speakers – a device that converts electrical energy to sound energy (waves)energy (waves)– The stored digital code representing the sound waves is The stored digital code representing the sound waves is

converted by the sound card into an analog signal which is then converted by the sound card into an analog signal which is then sent to the speakerssent to the speakers

– The speaker cone vibrates at a rate proportional to the strength The speaker cone vibrates at a rate proportional to the strength and frequency of the analog electrical signaland frequency of the analog electrical signal

Sound Cards – Device that converts analog audio to digital Sound Cards – Device that converts analog audio to digital audio and digital audio to analog audio. The output is a low audio and digital audio to analog audio. The output is a low level, so an amplified speaker system is required.level, so an amplified speaker system is required.– Most sound cards today are purchased as PCI adapter cards. Most sound cards today are purchased as PCI adapter cards.

This means they are usually PnP technology.This means they are usually PnP technology.– System resources (IRQ, DMA, I/O, Memory) are automatically System resources (IRQ, DMA, I/O, Memory) are automatically

detected and assigned.detected and assigned.