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Chapter 5 *

Printers *

Certification Objectives *

Printer Operations and Components *

Types of Printers *

Daisy Wheel Printers *

Dot Matrix Printers *

Bubble-Jet Printers *

Laser Printers *

Common Field Replaceable Units (FRUs) *

Paper Feeder Mechanisms *

Primary Power Supply Boards or Assemblies *

High-Voltage Power Supplies *

System (or Main Logic) Boards *

Sub Logic Boards *

Motors *

Fusers *

Rollers *

Sensors *

Switches *

Cables *

Printheads/Toner cartridges *

RAM SIMMs *

Care and Service Techniques *

From the Field *

The Printer Top-10 List *

Feed and Output *

Paper Jams *

Print Quality *

Laser Printers *

Blank Pages *

Speckled Pages *

"Ghosted" Images *

Smudged Images *

Bubble Jet *

Dot Matrix *

Printer Connections and Configurations *

Parallel *

Serial *

Network *

Infrared *

Certification Summary *

Two-Minute Drill *

 

Chapter 5

Printers

Certification Objectives

Printer Operations and Components
Care and Service Techniques
Printer Connections and Configurations

There’s no denying it. The business world revolves around paperwork. As the processing power of computers continues to increase, the need to put the data processed into a tangible, easy-to handle format called a hard copy becomes more and more apparent. It may be quite a while before industries that thrive on computer information services go totally paperless (if and when that ever occurs), so until then, the need for providing data in printed form will remain.

A printer is simply an electro-mechanical device designed to translate electronic impulses into a format that it can understand and transfer that format to a page. This chapter reviews the principles of operation, configuration, and maintenance of various printing devices. By the end of this chapter, you should have a working knowledge of all that’s involved with operating and servicing printers.

Printer Operations and Components

Printers are actually very simple devices. They exist for the sole purpose of taking the data that you see on your computer monitor and placing it on the printed page. Printers can be used to print documents from your favorite word processor, create envelopes, banners, labels, full-color photographic-quality images, and T-shirt transfers, just to name a few functions. This section upgrades your knowledge on the types of printers and their common field replaceable units (FRUs).

Types of Printers

There are many different types of printers available on the market, each having its advantages and disadvantages. When choosing a printer, it’s best to determine what your needs are and select a printer that best meets those needs. It really comes down to what the printer is going to be used for. Printers can be classified into two major groups: Impact and Non-impact. Impact printers, like the name suggests, require the impact with an ink ribbon to print characters and images. Non-impact printers do not use an ink ribbon, and therefore do not require direct contact with the paper for printing. The easiest way to differentiate between an impact and a non-impact printer is to determine whether or not multi-part form documents could be printed with them. Images and characters formed on impact printers are actually impressed upon the page, creating copies on all pages, whereas non-impact printers do not.

Daisy Wheel Printers

Daisy wheel printers are the first and most archaic type of impact printers we discuss. They have a wheel with raised letters and symbols on it that looks like a daisy, which is how the printer got its name. This type of printer is probably the computer peripheral most similar to the typewriter. When the printer receives the command to print a character, it sends a signal to the print head, which, in turn, spins the wheel on the print head until the appropriate character lines up. An electromechanical hammer (also called a solenoid or resistive coil) is energized, causing it to strike the back of the "petal" containing the character. The character impacts a printer ribbon, which then strikes the paper, leaving the image of the character in its place.

Daisy wheel printers were one of the first types of printers developed. Though they are not the fastest printers available, the advantage these have is that they are very capable of creating multi-part forms, which are still used by small businesses today. The main disadvantage of this type of printer is the amount of noise it creates from banging the characters against the page. Although measures have been taken in design to muffle the noise from these machines, they still remain the noisiest printers available.

Dot Matrix Printers

All dot matrix printers form characters and images a few dots at a time. They perform this by creating the image or character in a "matrix" of dots, hence the name dot matrix. There are two modes by which these types of printers can operate: Font mode, and dot-addressable.

In Font mode, the printer already has all the pins programmed for every character in its font set. When the printer receives the message to print the letter "R," for example, it looks up the letter "R" in its character table in ROM and sends the correct pin sequence to the print head. This allows a single input to produce many dots on the page, representing the character desired.

In dot-addressable mode, each printed dot requires an input. This provides for a lot of flexibility to users because they are not limited by the fonts available in the printer’s memory, but only limited by the software they use. The downside to this mode is that this printing method is much slower than font mode, because multiple dots require multiple inputs.

The print head on a dot matrix printer is a series of pins each controlled by its own solenoid (or resistive coil), which is similar in function to the solenoid on a daisy wheel printer. When the solenoid is energized, the pin is forced away from the print head and impacts the printer ribbon and ultimately the paper, thus impressing the dot on the page. Like the daisy wheel, the advantage of this type of printer is that multiple-page paper may be fed through, as in making carbon copies. The earliest print heads had 7 pins, whereas printers today have up to 24.

When a solenoid is energized on the printhead, its associated pin is forced outward coming into contact with the printer ribbon and finally impacting the page, creating a dot. The print head travels horizontally along the page, striking dots all along the way. It may take several passes to create one line of characters. Some printers are bi-directional, printing both from left to right and from right to left, whereas older dot matrix printers only printed in one direction.

Color of the output is dependent upon the color of the printer ribbon that is installed in the printer. Early dot matrix printers were limited to a single color printer ribbon, but today’s models offer ribbons with multiple colors, allowing for color output.

Bubble-Jet Printers

Unlike daisy-wheel and dot matrix printers, where contact with the paper is required, bubble-jet printers do not require contact with the paper. By use of small nozzles on the print head, a bubble-jet printer "spraypaints" the image on to the page.

Bubble-jet printers are actually an advance in technology from the older ink jet printers. Ink jet printers used an ink reservoir, pump, and ink nozzle to put the ink on the page. This method was inefficient as well as noisy and messy. Bubble jet printers improved on this concept by changing the means by which the ink is propelled towards the page.

Every bubble jet printer operates the same way. Bubble jets are comprised of a disposable ink cartridge that contains the print head nozzles and ink reservoir. This ink cartridge must be replaced when the ink runs out. Although possible, it is not recommended to have the cartridges re-filled with ink. Replacing the cartridges not only provides the printer with a fresh source of ink, but it replaces the nozzles that get worn out by the bubble jet process.

Inside the ink cartridge are several chambers. At the top of each chamber is a metal plate with a tube leading to the ink supply. The bottom of each chamber contains a single microscopic pinhole used to spray the ink onto the page. The print head passes across the page horizontally, just like a dot-matrix, spray-painting each dot along the way.

When a chamber receives the command to spray ink, an electrical signal is sent to energize the heating element. The heating element, in contact with the ink, heats up very quickly causing the ink to vaporize, resulting in a build up of pressure in the chamber. This pressure forces the ink out the pinhole forming a "bubble" of ink on the page. As the vapor expands, the bubble gets large enough to break off into a droplet. The rest of the ink is drawn back into the chamber due to the surface tension of the ink. This process is repeated for each drop that needs to be sprayed.

Laser Printers

Laser printers are an entirely different breed of printers all together. Using a combination of light, electricity, chemistry, pressure, and heat, they have the ability to create very high-quality images and text on the printed page. Lasers are classified as non-impact type printers.

Laser printers are also referred to as page printers because they receive their print job instructions one page at a time. Laser printers can perform this feat through use of a Page Description Language (PDL). Rather than the printer receiving instructions for each dot on the page, the PDL encoded in the printer receives commands from the computer on how to print the page. Using simple line drawing commands rather than printing each dot along that line greatly simplifies the instructions that must be passed to the printer.

The main components of a laser printer are listed as follows:

Cleaning Blade This rubber blade extends the length of the photosensitive drum. It removes excess toner after the print process has completed and deposits it into a reservoir for re-use.
Photosensitive Drum This light-sensitive drum is the core of the electrophotographic process inside the printer. This drum is affected by the cleaning, charging, writing, and transferring processes in the six-step printing process we discuss in detail later in this section.
Primary Corona Wire This highly negatively charged wire is responsible for electrically erasing the photosensitive drum, preparing it to be written with a new image in the writing stage of the print process.
Transfer Corona This roller contains a positively charged wire designed to pull the toner off of the photosensitive drum and place it on the page.
Toner Toner is comprised of finely divided particles of plastic resin and organic compounds bonded to iron particles. It is naturally negatively charged, which aids in attracting it to the written areas of the photosensitive drum during the transfer step of the printing process.
Fusing Rollers These rollers comprise the final stage of the Electrophotographic Printing (EP) printing process, bonding the toner particles to the page to prevent smearing. The roller on the toner side of the page has a non-stick surface that is heated to a high temperature to permanently bond the toner to the paper.
Exam Watch: Understanding the theory of the Electrophotographic Print process is a key to passing the Printers section of the exam.

The Electrophotographic Printing (EP) process for putting the image on the page is divided up into six distinct steps. Though some sources disagree on which step occurs first, the important thing to remember is that this process occurs as a cycle within the printer, so order of the steps is critical. During this process, the printer cleans and charges the photosensitive drum to prepare it for the image. A laser beam "writes" the data to the drum. Toner is then attracted to the areas of the drum where the laser "wrote" the image. The image is then transferred and bonded to the page for final output. Each step of this process is explained as follows:

  1. Cleaning Before any image formation can occur, the photosensitive drum must be cleaned and electrically erased.
    For the photosensitive drum to be cleaned, a rubber blade extending the length of the drum gently scrapes away any residual toner left over from the previous cycle. If this step is omitted, you would see random specks of black on your printed documents. The toner that is removed is deposited in a debris cavity or recycled for use again in the main toner supply area.
    Electrical erasure is accomplished by a series of erasure lamps aligned within close proximity of the photosensitive drum. The photosensitive drum is just that–photosensitive. Any light at all will erase the image on it. This step ensures that the drum has been electrostatically erased so that it can receive a new image.
    Now the photosensitive drum is ready to for the next step, charging.
  2. Charging Charging involves applying a high-voltage negative charge to the photosensitive drum. The voltage can reach as high as –5000Vdc. Because the primary corona wire and the photosensitive drum share a common ground, applying a large negative charge to the corona wire creates an electrical field between the two. At low voltages, the primary corona would have no effect on the photosensitive drum, but when a high voltage is applied, this ionizes the air gap between the wire and the drum. This ionization causes negative charges within the drum to migrate to the surface.
  3. Writing Now that the photosensitive drum has been prepared, the writing process can begin. A laser sweeps the entire length of the drum, cycling on and off with respect to the image to be created. When the laser is "ON," this neutralizes the highly negative charge on the drum, making the point where the laser strikes much less negative, almost neutral (approximately –100Vdc). The laser is precisely turned on and off as it sweeps across the drum, optically "writing" the image to the drum.
  4. Developing So far, the only evidence of an image in the printer is a series of highly negative and almost neutral charges across the photosensitive drum. The electrostatic image must be converted into a visual image before it can be transferred to the paper. Because the toner is negatively charged by nature, it is attracted to the areas of the photosensitive drum that are less negatively charged. Because the remaining areas of the drum are highly negatively charged, the toner will not be attracted to these areas. Finally, the image is beginning to take form, but we’re not there yet.
  5. Transferring Once the image has been set in toner on the photosensitive drum, it must be transferred to the print media, the paper. Because the toner is attracted to the drum, it must be pried away by an even stronger charge to get it to the paper. A transfer corona is a positively charged wire positioned on the opposite side of the paper that is used to serve this purpose. The transfer corona creates a strong positive charge on the paper sufficient to pull the toner particles from the drum. Once the toner is on the paper, the only forces holding it in place is a weak electrostatic charge on the paper and gravity.
  6. Fusing Due to the electrostatic properties of toner, it will stick to about anything. Toner has a negative static charge and the paper has a positive charge. In order to permanently bond the toner particles to the paper, a fusing process must take place. If this step were omitted, the toner would smear and smudge on the page, not creating a very professional look. The paper is pressed firmly between two rollers, one being a nonstick roller. The nonstick roller is heated by a high intensity lamp, creating the heat necessary to bond the toner to the page.

Common Field Replaceable Units (FRUs)

There are several components that function together to make a printer work. These components make the printer more modular in design and facilitate the replacement of these components should they fail. Rather than having to replace the whole printer when it fails, you simply replace the component that failed. As you’ve read in previous chapters of this book, these components are known as Field Replaceable Units (FRUs). All printers’ FRUs are removed and installed in different manners, so it’s important that you consult the manufacturer’s guidelines when replacing these components.

Paper Feeder Mechanisms

The role of the paper feeder mechanisms is to move the paper through the printer as images and text are printed to it. These mechanisms are in place to get the paper from the paper tray, through the printer, and out to the output tray.

Primary Power Supply Boards or Assemblies

Primary power supply boards provide power to the entire unit. This power is distributed to the various circuits within the printer.

High-Voltage Power Supplies

For laser printers, the EP printing process requires high-voltage electricity. It is the high-voltage power supply that provides this power. It steps up standard AC current (120V and 60Hz) to the higher voltage required for the printer. This high-voltage provides power to the primary corona and the transfer corona.

System (or Main Logic) Boards

The "brain" of the printer is the system board, shown in Figure 5-1. This board houses the central processing unit (CPU), which controls all the input and output within the printer.

Click Here To View Figure 5-1: Typical printer system board

Sub Logic Boards

Some printers may contain more than one board in their circuitry. Based on the design of the printer, it may have one or more dependent logic boards, as shown in Figure 5-2, for processing the data.

Click Here To View Figure 5-2: A printer’s sub logic board

Motors

The voltage is transformed down to approximately 24Vdc to provide power to the various motors used to move the paper through the printer. The main motors that are found within printers are:

Main drive
Paper feed
Transport

Installation of printer motors vary from type to type and model to model, so you must follow the manufacturer’s suggested guidelines for installation procedures. Figure 5-3 shows a typical printer motor.

Click Here To View Figure 5-3: Typical printer motor

Fusers

The fuser consists of three main parts: a halogen heating lamp, a rubberized pressure roller, and a Teflon-coated aluminum fusing roller. The fuser heats the fusing roller to anywhere from 165C to 180C. As the paper passes through the two rollers, the pressure roller forces the paper against the hot fusing roller, bonding the toner to the page.

Rollers

Rollers are located inside the printer to aid in the movement of paper through the printer (see Figures 5-4 and 5-5). There are four main types of rollers: feed, registration, fuser, and exit.

Click Here To View Figure 5-4: Printer rollers, front view

Click Here To View Figure 5-5: Printer rollers, side view

The feed rollers (also known as paper pickup roller), when activated, rotate against the top page in the paper tray and rolls it into the printer. The feed roller works together with a special rubber pad to prevent more than one sheet from being fed into the printer at a time.

The registration rollers synchronize the paper movement with the writing process inside the EP cartridge. The registration rollers do not advance the paper until the EP cartridge is ready to process the next line of the image.

Fuser rollers, as discussed previously, use a combination of heat and pressure to bond the toner to the paper.

Exit rollers aid in the transfer and control of the paper as it leaves the printer. Depending on the printer type, they direct the paper to a tray where it can be collated, sorted, or even stapled.

Sensors

Sensors, may be located in various places within the printer to aid in the paper movement during the printing process. For example, one sensor may detect a paper jam and send a signal to the printer control circuitry to generate an error message.

Switches

Switches (also called DIP switches) provide a means for the user to modify a preset hardware configuration to meet his or her particular needs for the printer. For example, a DIP switch might control whether the printer defaults to printing in draft mode or letter quality. The use of these switches is diminishing as more and more printers are designed with flashable firmware that allows the printer configuration to be updated with software.

Cables

Cables for the most part are the means of connecting the computer to the printing device. There are normally three separate cable types used to provide the connectivity: parallel, serial, and network.

A parallel cable consists of a male DB-25 connector that plugs into the computer and a male 36-pin Centronics connector that connects to the printer. The recommended length for a parallel cable is ten feet. Lengths any longer than ten feet run the risk of crosstalk, which causes signal degradation and communications to become unreliable.

Serial cables consist of either a DB-9 or DB-25 female connector that plugs into the computer to a DB-25 male connector that plugs into the printer. Because information on a serial cable is only traveling along one wire, serial cables are not as susceptible to crosstalk as are parallel cables, and the cable length can extend up to 25 feet.

Network cables vary from network to network, depending on the media type of the network. Most printers configured with a network interface provide a standard RJ-45 type connector (looks very much like a phone cable). The maximum recommended cable length is specified by the type of network the printer is connected to (for example, a 10BASE2 Ethernet network maximum segment length is 185 meters).

Other types of field replaceable cables may be found inside of the printer assembly. These cables may connect power supplies, motors, print heads, and other components to each other as required. The number and type of cables inside the printer can usually be found in the technical manual.

Exam Watch: Minimize your cable lengths for reliable communications. Parallel cables should be limited to 10 feet; serial cables to less than 25 feet.

Printheads/Toner cartridges

Print heads and toner cartridges are just about the only FRUs that the printer manufacturer gives the end user responsibility for replacing. Most print quality problems can be remedied by replacement of these components.

RAM SIMMs

Just like a computer, a printer’s memory can also be upgraded. Installing additional memory in a printer greatly enhances the amount of information the printer can retain during a print job. This is good news to the computer, because it can resume with other applications and processes once the print job has been completely sent to the printer.

Care and Service Techniques

Proper care and service of the printer greatly extends the life of the printer and maintains the quality of the documents processed. Like the engine in your car, proper care and maintenance will keep the printer operating and performing like new for many years.

From the Field

The Printer Top-10 List

Studies have proven that printers are the cause of the most help desk calls. Here are the top ten causes of these printer calls:

  1. Bad driver for the printer installed.
  2. Dirty rollers.
  3. Ink or laser cartridges empty.
  4. Paper jam.
  5. Bad print job clogging the print que.
  6. Poorly formatted document sent to printer.
  7. Actual mechanical breakage.
  8. Open paper cabinets, panels, and so forth.
  9. Network problems (on network printer).
  10. Improper media used.

Printers can be very confusing for new users. If I had a dollar for every "out of paper" ink jet call I’ve had …. Improper media can practically ruin a printer. Have you ever seen mailing labels sent through an inkjet that rolls the paper instead of keeping it flat? Not a pretty site or a joy to clean up. The all-too-frequent call about a dead printer that is simply turned off will start to get annoying. Assume nothing when troubleshooting a printer—It could be something really obvious or highly complex. Printer problems may stem from software, network, and cabling problems. There are printer problems that have nothing to do with the printer except for how that particular model of the printer reacts to what is being sent as a print job. Some applications mixed with some operating systems mixed with some network privileges mixed with certain computers mixed with certain printers will have problems. I’ve seen printer problems so mysterious that all the king’s horses and all the king’s men and Einstein to boot (plus 5 MCSE’s and Technet and Microsoft and Hewlett Packard) could not figure out. The only solution was to change computers and print the same print job from another computer. Not a total solution but it worked. The more you know about printers and their idiosyncrasies, the further you’ll excel in this field.

by Ted Hamilton, MCP, A+ Certified

Feed and Output

Most of the problems experienced when operating a printer fall into two major categories: feed and output. Either the printer doesn’t properly feed the paper, causing a paper jam, or the quality of the printer output is not as desired. We discuss the common problems experienced in these two areas in the following sections.

Paper Jams

Paper jams are one of the most frequent errors that occur in any machine that processes paper. They occur any time something goes wrong with the paper feeder assembly that would prevent proper feeding of the paper through the printer. They can be caused by the feeder mechanism inadvertently feeding two or more sheets of paper at the same time. Sometimes the paper can be torn and small pieces of paper get lodged in the paper path. Paper jams can happen for a variety of reasons, but are usually easily remedied by opening the printer and removing the faulty page. Some printers, especially laser printers, have interactive help that walks you through which compartment or paper tray to open to find the jam.

Print Quality

Print quality is usually affected by the failure of a printing mechanism or from the fact that the printer needs cleaning. Most print quality issues can be narrowed down to one of these two causes. Print quality problems vary with each type of printer. Some of the most common ones are covered in the following sections.

Safety Precautions

In addition to observing basic electronic safety precautions, there are a few things to keep in mind when working with printers. All printers are composed of moving parts that advance the paper through the machine. Be sure that you don't have any loose clothing, or you may find your tie or clothing caught on the plate or other moving parts inside the printer.

Another thing to keep in mind is that components inside a printer can
be very dirty. Be careful with your hands around your own clothing and especially around a customer's work area. Everything from ink, toner, and grease is easily spread from one area to another and is difficult to clean.

There are specific tools and measurement equipment provided by the manufacturer for cleaning and to verify proper laser operation. Never take shortcuts with the recommended procedures. Also, some printers have built-in safety interlocks to prevent technicians from injuring themselves. Never override an interlocked switch without being advised to do so by the printer service manual.

 

Preventive Maintenance

One of the easiest ways to ensure trouble-free operation of a printer is by performing periodic preventive maintenance. Although the thought of performing maintenance may not be appealing, taking a few minutes every few months can save you lots of money and unnecessary downtime. Simply put, non-performance of preventive maintenance can lead to expensive, more time-consuming corrective maintenance. As with any piece of equipment you're performing maintenance on, always refer to the procedures outlined in the appropriate user and/or service manuals.

Most printer technical manuals will outline the maintenance
that should be performed. The most common types of maintenance include vacuuming, cleaning, lubricating interior components, and general cleanliness of the external case. As you've learned, each printer is designed and put together differently, requiring different methods of cleaning and troubleshooting. Keep this in mind as you work on a printer. When in doubt, follow the procedure.

Laser Printers

Print quality problems that can occur with laser printers include the following:

Blank pages
Speckled pages
Ghosted images
Smudge images

Blank Pages

There’s nothing more frustrating than sending a print job to a printer and having it spew out page after page of nothing. Most of the time, this is caused by an application on the computer sending corrupt data, but other reasons a laser printer may send blank pages include:

No toner If there’s no toner in the cartridge, no images will be transferred to the page.
Transfer Corona failure If this wire fails, no toner will be attracted from the photosensitive drum to the paper.
HVPS failure If the high voltage power supply isn’t providing the voltage necessary to either the primary corona or transfer corona, the printing process will not work correctly.

Speckled Pages

Sometimes a print job may result in little specks of black on the page, random or not. This may be due to a failure of the cleaning step of the EP printing process. Another cause may be a scratch or defect in the EP drum, causing toner to remain in these recesses during the cleaning step.

"Ghosted" Images

"Ghosting" is what occurs when a portion of the image previously printed to the page is printed again, only not as dark. One cause of this is if the erasure lamp fails to operate correctly, not completely erasing the previous image from the EP drum. Another cause of ghosting may be due to a malfunction in the cleaning blade such that it doesn’t adequately scrape away the residual toner.

Smudged Images

If an image smudges, then an element of the fusing process has failed. This could be a result of the halogen lamp burning out, failing to melt the toner to the page.

Bubble Jet

The majority of problems experienced with bubble jet printers are print quality issues. Most of these issues can be resolved by replacing the ink cartridge. If the printer sits idle for a prolonged period of time (a week or more), the ink can dry out in the printhead nozzles and clog them.

Exam Watch: A corrective measure for a dry ink cartridge should never be refilling the ink cartridge! Replacing the cartridge not only replenishes the ink, but replaces the old worn-out nozzles with new ones.

Dot Matrix

Dot matrix print quality issues normally boil down to two things: ribbon replacement or print head replacement. If the output is beginning to fade, it is time to change the ink ribbon. If there are white horizontal streaks on your page, this would indicate that a pin is not firing, requiring the print head to be replaced.

Printer Connections and Configurations

There are a variety of ways to provide a connection between your computer and the printing device. Current connections make use of the ports available on the back of your machine, and, if you’re on a network, the use of a network connection. There are three major types of connection methods: parallel, serial, and network. A connection method that is not yet as common but has its place in this section is infrared, which is discussed briefly. Other connection methods may be available, but are not as commonly used as the methods discussed here.

Parallel

Most printers are configured to communicate via the parallel port. The parallel port consists of a 25-pin connection that allows transmitting of information along eight different wires (hence parallel). When a printer uses parallel communications, it transmits 1 bit per wire, giving it the ability to transmit 8 bits at a time (1 byte). The parallel port allows for fast communication, which is needed especially when transmitting complex images and graphics to the printer.

Serial

Some printers can be configured to communicate via the serial port. When a printer uses serial communications, it transmits one bit at a time along a single wire. Similarly to modems, the serial port must be configured with communication parameters (bps, parity, start and stop bits,and so forth) on both the printer and the computer before communications can occur.

The serial port consists of either a 25-pin or 9-pin connection that allows transmitting of information along a single wire. Each bit is sent one after another in a single file line. Because there is only a single wire carrying the transmission, serial cables are not as susceptible to crosstalk as parallel cables are. Cable lengths for serial cables may extend up to 25 feet with no signal attenuation.

Network

Some of the more recent printers coming out on the market have a special interface that allows them to be accessed on a network. These printers come equipped with a network interface card (NIC) that allows it to be plugged directly into the network. ROM-based software allows the printer to communicate with the servers and workstations on the network.

Because virtually everyone in an office environment needs access to a printer, buying a printer for each workstation is not the most economic solution. Networked environments allow for many different users to share printer resources, saving thousands of dollars on printer costs. Printers can be shared when plugged into a workstation through the parallel or serial port, but this requires that the workstation be up and running in order to share that resource.

Infrared

A recent development in printer technology now allows data communications to exist over a beam of light. Some laptops are equipped with an infrared serial port that allows you to transmit to any device that has an infrared port just as if you were physically connected. This is a line-of-sight technology, which requires that the transmitting port be directed to the infrared interface on the printer. We will not go into great detail in this method of printer communication but you should know that the method is available.

Certification Summary

There are a variety of ways of presenting information on the written page. Having an understanding of the different printing technologies and a logical method of troubleshooting problems when they arise will not only help you out on the A+ examination, but is invaluable information as a technician in the computer industry. The majority of what you will learn about printers will more than likely be from hands-on experience, where the printer’s technical manual should be your guide.

Two-Minute Drill

A printer is simply an electro-mechanical device designed to translate electronic impulses into a format that it can understand and transfer that format to a page.
Printers can be classified into two major groups: impact and non-impact.
Daisy wheel printers have a wheel with raised letters and symbols on it that looks like a daisy, which is how the printer got its name.
One advantage of daisy wheel printers is that they are very capable of creating multi-part forms, which are still used by small businesses today.
In the Font mode of a dot matrix printer, the printer already has all the pins programmed for every character in its font set. In dot-addressable mode, each printed dot requires an input.
The print head on a dot matrix printer is a series of pins each controlled by its own solenoid (or resistive coil), which is similar in function to the solenoid on a daisy wheel printer.
The earliest dot matrix print heads had 7 pins, whereas printers today have up to 24.
By use of small nozzles on the print head, a bubble-jet printer "spraypaints" the image on to the page.
Replacing the ink cartridges on a bubble jet printer not only provides the printer with a fresh source of ink, but it replaces the nozzles that get worn out by the bubble jet process.
Using a combination of light, electricity, chemistry, pressure, and heat, laser printers have the ability to create very high-quality images and text on the printed page.
Laser printers are also referred to as page printers because they receive their print job instructions one page at a time.
The main components of a laser printer are: cleaning blade, photosensitive drum, primary corona wire, transfer corona, toner, and fusing rollers.
The six-step EP process is as follows: Cleaning, Charging, Writing, Developing, Transferring, and Fusing. Know this procss!
During the Cleaning step of the EP process, he toner that is removed is deposited in a debris cavity or recycled for use again in the main toner supply area.
The Charging step of the EP process involves applying a high-voltage negative charge to the photosensitive drum. The voltage can reach as high as –5000Vdc.
In the six-step EP process, an image begins to appear in the Developing step.
In order to permanently bond the toner particles to the paper in the laser printing process, a fusing process must take place.
The main motors that are found within printers are the main drive, paper feed, and transport motors.
The fuser consists of three main parts: a halogen heating lamp, a rubberized pressure roller, and a Teflon-coated aluminum fusing roller.
There are four main types of rollers: feed, registration, fuser, and exit.
Switches (also called DIP switches) provide a means for the user to modify a preset hardware configuration to meet his or her particular needs for the printer.
There are normally three separate cable types used to provide printer connectivity: parallel, serial, and network.
A parallel cable consists of a male DB-25 connector that plugs into the computer and a male 36-pin Centronics connector that connects to the printer.
Minimize your cable lengths for reliable communications. Parallel cables should be limited to 10 feet; serial cables to less than 25 feet.
Most print quality problems can be remedied by replacement of the print head or toner cartridges.
Most of the problems experienced when operating a printer fall into two major categories: feed and output.