What is Printer & it's Types

Printer

Printers are Output devices used to prepare permanent Output devices on paper. Printers can be divided into two main categories:

Character Printer

 It prints only one character at a time. It has relatively slower speed. Eg. Of them are Dot matrix printers.

Dot matrix

 A type of impact printer that produces characters and illustrations by striking pins against an ink ribbon to print closely spaced dots in the appropriate shape. Dot-matrix printers are relatively expensive and do not produce high-quality output. However, they can print to multi-page forms (that is, carbon copies), something laser and ink-jet printers cannot do. 

Dot-matrix printers vary in 3 important characteristics:

Speed: Given in characters per second (cps), the speed can vary from about 50 to over 500 cps. Most dot-matrix printers offer different speeds depending on the quality of print desired.

Print quality: Determined by the number of pins (the mechanisms that print the dots), it can vary from 9, 18 or 24pins. The best dot-matrix printers (24 pins) can produce near letter-quality type, although you can still see a difference if you look closely.

Ink: Dot Matrix Printer use ribbon for ink

Ink-jet

A type of printer that works by spraying ionized ink at a sheet of paper. Magnetized plates in the ink's path direct the ink onto the paper in the desired shapes. Ink-jet printers are capable of producing high quality print approaching that produced by laser printers. A typical ink-jet printer provides a resolution of 600 dots per inch, although some newer models offer higher resolutions.

Speed: Given in Pages per Minute (PPM) the higher the PPM the more pages they can print. Most ink-jet printers offer different speeds depending on the quality of print desired.

Print quality: Determined by the DPI Dot Per Inch Example 2440 x 1220 DPI (Vertical and Horizontal DPI) The higher the DPI the better in terms of print quality.

Ink: Ink-Jet Printers use Ink Cartridges (hidden cost)

In general, the price of ink-jet printers is lower than that of laser printers. However, they are also considerably slower. Another drawback of ink-jet printers is that they require a special type of ink that is apt to smudge on inexpensive copier paper. 

Because ink-jet printers require smaller mechanical parts than laser printers, they are especially popular as portable printers. In addition, color ink-jet printers provide an inexpensive way to print full-color documents.

Laser

A type of printer that utilizes a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. This is also the way copy machines work.

Speed: Given in Pages per Minute (PPM) the higher the PPM the more pages they can print. Most ink-jet printers offer different speeds depending on the quality of print desired.

Print quality: Determined by the DPI Dot Per Inch Example 4880 x 2440 DPI (Vertical and Horizontal DPI)

Ink: Laser Printers use Toner Cartridges

Laser Printer Parts

• Toner Cartridge Components 
• EP Photosensitive Drum
• Erase Lamp
• Primary Corona Wire
• Toner 
• Transfer Corona
• Fuser
• Power Supplies
• Turning Gears
• Motherboard
• Ozone Filter
• Sensors
• Switches

Because an entire page is transmitted to a drum before the toner is applied, laser printers are sometimes called page printers. There are two other types of page printers that fall under the category of laser printers even though they do not use lasers at all. One uses an array of LEDs to expose the drum, and the other uses LCD's. Once the drum is charged, however, they both operate like a real laser printer.

One of the chief characteristics of laser printers is their resolution -- how many dots per inch (dpi) they lay down. The available resolutions range from 300 dpi at the low end to 1,200 dpi at the high end. By comparison, offset printing usually prints at 1,200 or 2,400 dpi. Some laser printers achieve higher resolutions with special techniques known generally as resolution enhancement. 

In addition to the standard monochrome laser printer, which uses a single toner, there also exist color laser printers that use four toners to print in full color. Color laser printers tend to be about five to ten times as expensive as their monochrome siblings. 

Laser printers produce very high-quality print and are capable of printing an almost unlimited variety of fonts. Most laser printers come with a basic set of fonts, called internal or resident fonts, but you can add additional fonts in one of two ways: 

Font cartridges: Laser printers have slots in which you can insert font cartridges, ROM boards on which fonts have been recorded. The advantage of font cartridges is that they use none of the printer's memory.

Soft fonts: All laser printers come with a certain amount of RAM memory, and you can usually increase the amount of memory by adding memory boards in the printer's expansion slots. You can then copy fonts from a disk to the printer's RAM. This is called downloading fonts. A font that has been downloaded is often referred to as a soft font, to distinguish it from the hard fonts available on font cartridges. The more RAM a printer has, the more fonts that can be downloaded at one time. 

In addition to text, laser printers are very adept at printing graphics. However, you need significant amounts of memory in the printer to print high-resolution graphics. To print a full-page graphic at 300 dpi, for example, you need at least 1 MB (megabyte) of printer RAM. For a 600-dpi graphic, you need at least 4 MB RAM. 

Because laser printers are no impact printers, they are much quieter than dot matrix. They are also relatively fast, although not as fast as some dot-matrix printers. The speed of laser printers ranges from about 4 to 20 pages of text per minute (ppm). A typical rate of 6 ppm is equivalent to about 40 characters per second (cps). 

Laser printers are controlled through page description languages (PDL's). There are two de facto standards for PDL's: 

PCL: Hewlett-Packard (HP) was one of the pioneers of laser printers and has developed a Printer Control Language (PCL) to control output. There are several versions of PCL, so a printer may be compatible with one but not another. In addition, many printers that claim compatibility cannot accept HP font cartridges.

PostScript: This is the de facto standard for Apple Macintosh printers and for all desktop publishing systems. 

Most software can print using either of this PDL's. PostScript tends to be a bit more expensive, but it has some features that PCL lacks and it is the standard for desktop publishing. Some printers support both PCL and PostScript

1. Cleaning – The Photosensitive drum is cleaned before it can take on a new image
2. Conditioning or Charging – To make the drum receptive to new images, it must be charged. The EP drum is given a negative charge by the primary corona wire around -600 and -1000 volts
3. Writing - A laser beam is use to write to the EP drum causing dots on the drum to lose some of the negative charge and become relatively positive charge
4. Developing - A toner is transferred from the toner cylinder to the EP drum by attracting the area of the drum that has a Relative positive charge
5. Transferring - The transfer corona wire puts a highly positive charge on the paper once the paper has a positive charge the negatively charge toner particle leaps from the drum into the paper 
6. Fusing - The compression roller and fusing roller press and melts the toner into the paper the fuser gets very hot

Other Types of Printers

Photo Printer 

Is a type of printer use for printing photographs.

Dye-Sublimation Printer 

Is a type of printer which employs a printing process that uses heat to transfer dye to a medium such as a plastic card, printer paper or poster paper.

Thermal Printer

Is a type of printer that produces a printed image by selectively heating coated thermo chromic paper, or thermal paper as it is commonly known, when the paper passes over the thermal print head. The coating turns black in the areas where it is heated which then produce an image.

All-in-One Printer

A printer than can also do scanning, fax and make copies

Plotter 

A large device use to print large posters and documents

Hard Disk

What is a Hard Disk?

Hard disks were invented in the 1950s. They started as large disks up to 20 inches in diameter holding just a few megabytes. They were originally called "fixed disks" or "Winchesters" (a code name used for a popular IBM product). A hard disk drive consists of a motor, spindle, platters, read/write heads, actuator, frame, air filter, and electronics.

The first computer with a hard disk was IBM’s RAMAC, which was used during the 1960 Olympics to calculate sports results. A bit later, in 1962, removable disk packs were developed – a forerunner of the floppy disk. In 1964, the CRC algorithm was introduced. It provided greater security by checking and comparing data before and after it was written to the disk. In 1971, the first 8-inch diskettes came onto the market.

But it wasn’t until the middle of the 1980’s that people began to use hard disks in more standard PC’s, and since then development has surged ahead. The capacity of a standard hard disk has actually become a thousand times greater in the period 1990-2000.

The standard user’s need for disk space (e.g. for digital photos, video and music) has grown in step with this, so that 120-250 GB of disk space or more is normal in many PC’s – a figure which will double over the next few years.

Hard disks are constantly being developed which have greater capacity and speed (the two go together, as we shall see), and there is therefore a constant need for new types of hard disk controllers. The companies leading the development are Maxtor, Western Digital, IBM/Hitachi and Seagate.

The frame mounts the mechanical parts of the drive and is sealed with a cover. The sealed part of the drive is known as the Hard Disk Assembly or HDA. The drive electronics usually consists of one or more printed circuit boards mounted on the bottom of the HDA.

How Hard Disk Works?

Data on a hard disk is stored in microscopic areas called magnetic domains on the magnetic material. Each domain stores either a 1 or 0 value. Similar to a floppy disk, a hard disk records its data in concentric circles or tracks, which are numbered from the outermost edge to the innermost edge of the platter. These tracks are further subdivided into smaller units called sectors which typically store 512 bytes of data each. Zoning may be needed to further optimise the data storage as the outer circumference would normally pack more sector units than the inner circumference.

·         When a command is made to store some data on a disk, the following chain of events occurs:

·         The data flows into a cache where it is encoded using special mathematically derived formulae, ensuring that any subsequent errors caused by noise can be detected and corrected.

·         Free sectors on the disk are selected and the actuator moves the heads over those sectors just prior to writing. (The time it takes the actuator to move to the selected data track is called the "seek" time.)

·         Once over the data track, the heads must not write the data until the selected free sectors on that track pass beneath the head. This time is related to the rotation speed of the disk: the faster the speed, the shorter this "latency" period.

·         When it's time to write, a pattern of electrical pulses representing the data pass through a coil in the writing element of the recording head, producing a related pattern of magnetic fields at a gap in the head nearest the disk. These magnetic fields alter the magnetic orientations of bit regions on the disk itself, so the bits now represent the data.

When a command is made to read some data on a disk, a similar process occurs in reverse. After consulting the table of stored data locations in the drive's electronics, the actuator moves the head over the track where the chosen data is located. When the correct sectors pass beneath the head, the magnetic fields from the bits induce resistivity changes in the sensitive MR or GMR materials located in the reading elements within the head. These elements are connected to electronic circuits, and the current flowing through those circuits change with the resistivity changes. The current variations are then detected and decoded to reveal the data that had been stored on the disk.

Types of Hard Disks

There are few different types of hard disks, but other than its physical size, the different type of interfaces of the hard disk is main difference.

1. IDE: Integrated Drive Electronics. IDE drives are also known as PATA drives (Parallel advance technology attachment)

2. SATA: Serial advance technology attachment

3. SCSI

Small Computer System Interface. SCSI is pronounced as scuzzy.

1. IDE / PATA (Integrated Drive Electronics Drive / Parallel Advance Technology Attachment Drive)

1. IDE/PATA Drives have usually Interface Connector 40 pins & Power Connector 4 Pins.
2. IDE/PATA Drives offer 133 MB/sec transfer rate.
3. It sends 8 bit data at a time. 
4. PATA Cables are used to connect PATA HDD. Two drives can be connected in a single pata cable. One as master and other as slave. The configuration of master and slave is done by different combination of jumpers in the HDD.

2.SATA (Serial AdvancTechnologyAttachment  Drive)

1. SATA Drives have usually 7 pins, 4 pins in pair of two for sending and receiving data and rest 3 pins are grounded and Poer Connector 15 pins & 4 Pins .
2. SATA Drives offers generally 300MB/sec transfer rate.
3. It sends data bit by bit.
4. SATA Cables are used to connect SATA HDD. Only one drive can be connected in a single sata cable

3. SCSI (Small Computer System Interface Drive)

1. SCSI Drives have usually 50 to 68 pins and Power Connector 4 Pins
2. SCSI Drive offers generally 640MB/sec transfer rate.
3. This drives are hot swappable. 
4. SCSI cables are used to connect SCSI HDD. Maximum of 16 drives can be connected in a single scsi cable. Each hdd have a 8 bytes hexadecimal code known as WWN (world wide name) for its identification in the cable.

LCD Monitor Repairing

Setup a work area with a soft cloth down so you do not scratch the screen.

Lay the monitor on its face or screen.

Remove the screws from the back.  

With the screws removed, the case will be slightly loose but the front and back will be held together by the internal clips. 

Look at the photos below to come to grips with what you are dealing with. It should go a long way in helping get the shell apart in only two pieces, as apposed to several pieces (which would be bad).

If you fingers are strong and your finger nails have an edge to them,  you may be able "gently" separate the two halves.

The best approach is to use a plastic putty knife to separate the front from the back. 

Start at the top or where the frame is the most sturdy. Thin edges near buttons are best left to last.

There's no easy way to do this.  Just be careful and avoid breaking the plastic clips.  Once the first clip comes free the rest comes apart much easier. Each model is different but they all have this basic design in common (clips and screws). Our test subject had three screws for the case and three more screws that attached the base.

Putty knife separating the shell

We've opened several of these now and found working from the side or top is the best place to start. Once the 1st clip lets go rotate and open the rest of the clips. As the clips open the rest comes easy

Remove the back

Remove the shielding if there is any.

Check your cables

Photo showing the plastic clips on the front and back of the shell.

You can see a series of clips which hold the shell together.

Number the connectors before you remove them. Write the numbers on the socket and plug for each match up later.

Once you get the case open, the hardest part is behind you.  
Disconnect the cable running from the front panel to the chassis. (Use a sharpie to label the connector and socket)

Remove the shielding that covers the area near the power connector. 

Mark each connection with a Sharpie. Label ABC or 123 but you need to mark every connector and the corresponding socket with the same code.  This is critical because many of the connectors look exactly the same and are very close together.

Good example of confusing connectors that need to be labeled.

The image below shows the inverter board. It is a small board that is unique to your monitor's model. However, it has several cables attached and is considerably smaller than the monitor.

The power plug will be mounted directly on the inverter-board or wired to the inverter board.

The culprits are the electrolytic capacitors found on this board. These little guys dry out due to age, heat, and just plain being over worked. Most manufacturers use cheap capacitors and this is the reason why we are here and the reason we are going to do a better job than the manufacturer did.

Examine the inverter board for blown capacitors. All capacitors showing a rounded top are very bad. Some may be bad even if they do not show a rounded-top, but all with a rounded top must be replaced. Replacing all capacitors (sans the giant one in the middle) is the best idea.   Again you do not need to replace the giant capacitor unless it obviously bad. 

Watch the video above for a clear identification of where to find the bad capacitors.
The capacitors in the monitor are the cheapest available. You will want to replace them with the best available.
Capacitors used in consumer grade monitors have a life of 1000-2000 hours.  We are going to replace them with quality capacitors rated for a minimum life cycle of 6000-8000 hours. Even under heavy office use, these new capacitors should last five years. 

The video above compares a bad and good capacitor side by side.
Please note: Caps with bulging tops are bad but caps that look normal could still be dried up and dead.
So if your monitor tries to light up but fails to light up, this is a very likely cause.

The photo below above show the three worst capacitors, but I will be replacing eight capacitors on this board.
Notice how they bulge at the top? This is a dead give a way of a ruptured capacitor.

Document your capacitor locations.
Draw a map or just use your camera to take a photo of the inverter board and write the values on the photo.
The values will be in micro farads. The printing will look like "uF". You also need the voltage rating. Pick the best life cycle you can afford.

When buying capacitors for this job, you need polarized. If you do not buy polarized you will damage your monitor. A polarized capacitor is easily noted by the stripe with "-" symbol printed on one side.  This the negative leg and goes in the hole marked as negative on your circuit board. 

De-solder all capacitors.
Using a De-solder tool, vacuum out the solder and remove the caps.

Mount your inverter board.
Plug in all your cables using your sharpie numbers to guide you.
Before snapping the case back together, plug in the power cable and turn on the monitor.
After a few seconds, the monitor should detect there no video cable connected and it will display a message or test pattern.
That's all you need to see. Pull the power plug & put it back together.

Put the case halves back together.
This is easier than you can imagine so be sure you are ready. You do not want to crack it open again for a very long time. The two halves will act as if they want to be together.
With a slight press and a cascade of snapping latches, the two halves will become one again.
Install the screws and give it a final test. 

Monitor Repairing

Monitor

Problems of Monitor

1. Dead
2. No Screen Light (Raster) but Power on
3. No Vedio but having screen light
4. Dim Vedio but Good Screen Light
5. Spot on Monitor Power Off
6. Screen Flashing on Display
7. No Proper Color on Display
8. Horizontal Jacking on Display
9. Vertical Jacking on Display
10. Vertical line on Display
11. Horizontal Line on Display
12. Horizontal Scrolling on Display
13. High Frequency Sold in Monitor
14. Vedio Disappear after Some Time

1.Dead

1. Check the fuse
2. Check the 220 AC volt input
3. Check the DC volt a main capacitor 270V
4. Check the main transistor  of power supply
5. Check all the diode, Zanner diode, resistance around the main transistor
6. Change the power supply IC UC3842 (8 Pin) PWN

2. No Screen Light (Raster) but Power on

1. Check the heater light on CRT (Control Rays Tube)
2. Check the heater voltage 6V pin no third & fourth
3. Check the signal cable (VGA Cable)
4. Check the main horizontal output transistor horizontal section
5. Check all the resistance diode, transistor horizontal section

3. No Vedio but having screen light

1. Check the VGA cable
2. Check the dry sold in vedio section
3. Check all the transistor in vedio section
4. Check the red, green, blue voltage 70 to 100
5. Change the vedio IC

4. Dim Vedio but Good Screen Light

1. Check the amplifier transistor
2. Check the heater voltage
3. Change the CRT tube

5. Spot on Monitor Power Off

1. Change the CRT tube
2. Waving problem of display
3. Check the dry sold in main board
4. Change the main capacitor of power supply

6. Screen Flashing on Display

1. Check the dry sold in vedio section
2. Check the dry sold in horizontal section
3. Check the VGA cable

7. No Proper Color on Display

1. Check the VGA cable
2. Check the dry sold in vedio section
3. Check the (Red, Green, Blue) driver transistor in vedio section
4. Check the amplifier transistor in vedio section
5. Change the vedio IC

8. Horizontal Jacking on Display

1. Check the horizontal section dry sold
2. Check the horizontal hold variable
3. Check the dry sold horizontal Yolk coil connection

9. Vertical Jacking on Display

1. Check the vertical section dry sold
2. Check the vertical hold variable
3. Check the dry sold vertical Yolk coil connection

10 .Vertical line on Display

1. Check the dry sold in Yolk coil connection
2. Check the dry sold vertical section
3. Check all the resistance. Diode vertical section
4. Change the Vertical IC

11. Horizontal line on Display

1. Check the dry sold in Yolk coil connection
2. Check the dry sold horizontal  section
3. Check all the resistance. Diode horizontal section

12. Horizontal Scrolling on Display

1. Check the sync signal pin no 13 (VGA Cable)
2. Check the horizontal hold variable
3. Check the sync IC

13. High Frequency Sold in Monitor

1. Check the dry sold in horizontal section. (TDA 4586)

14. Vedio Disappear after Some Time

1. Check the dry sold in monitor
2. Power supply
3. Horizontal Section
4. Vertical section

15 Pin VGA Connector Pin Configurations

1	Red
2	Green
3	Blue
6	Red-Ground
7	Green-Ground
8	Blue-Ground
5	Ground
10	Ground
11	Ground
13	Horizontal Sync
14	Vertical Sync

PCB Neck Pins Configurations

1. Neutral
2. Bluck
3. Heater –
4. Heater +
5. Red “K”
6. Gris 2 “Brightness”
7. Green “K”
8. Gris 1
9. Neutral
10. Focus Grid 3