The concept of forming characters and graphics through the use of dot arrays took on a new life with the introduction of ink jet technology. Ink jet printers (Fig. 22-1) offer many of the advantages that impact printers had so long tried to achieve. Primarily, ink jet printing is quiet. It is also capable of printing high-resolution graphics, as well as color operation - two feats which impact printers never truly mastered. Finally, the power required to operate ink jet heads is far less than impact printers. Low power results in smaller power supplies, so ink jet printers are often small, efficient devices that are ideal for mobile printers used in conjunction with laptop computers. The quiet, low-cost, high-quality color printing afforded with ink jet printers is quickly displacing the older impact printers in homes and offices. This chapter is intended to illustrate the major assemblies of a typical ink jet printer, and show you a selection of troubleshooting procedures.

A typical ink jet printer is composed of four main areas as illustrated in the block diagram of Fig. 22-2; the print head, the paper transport, the carriage transport, and the electronic control unit (ECU). This chapter will touch on each of these sub-assemblies. As with impact printers, data sent from a host computer is interpreted by the printer's main logic (the ECU) and converted to a series of vertical dot patterns. Motor commands start the carriage (and print head) moving across the platen. Simultaneously, printer circuits will send each dot pattern to the print head in series. Each dot pattern fires the corresponding nozzles to leave a permanent mark on the page. This is also called "serial" or moving-head operation.

Ink jet print heads all have one characteristic in common - they never actually touch the page. Where impact printing relies on contact to deliver dots on a page surface, ink jet printing is a non-contact print technology. Ink is literally "spray-painted" onto the page. The mechanics that control this spraying process make up the ink jet print head. There are three classical techniques used in an ink jet print head; continuous flow, piezoelectric pump, and bubble pump. Since continuous flow printing is typically used for high-volume, low-quality industrial marking (i.e. putting expiration dates on milk containers), it will not be discussed in this book.

Generally speaking, a series of fine nozzles (each about 1/3 the diameter of a human hair) are arranged in vertical sets of 9, 12, 24, or more on the face of the print head. Nozzles themselves are little more than microscopic holes drilled into a metal face plate. As you might expect, nozzles are open to the air, but ink's surface tension prevents it from spilling out uncontrollably. Ink reaches each nozzle through a set of open channels, and is gravity-fed from a small ink reservoir which is built into the head (for disposable print heads) or located external to the head in a replaceable ink cartridge (for non-disposable print heads).

Each ink channel is connected to a series of electrical contacts used to operate the "ink pumps" built into every channel. It is these ink pumps which break up ink in the channels and form individual droplets that are ejected onto the page. There are two types of ink pumps; piezoelectric and thermal (or "bubble"). Pumps are fired independently by the printer's ECU. The control circuitry that interprets data and translates it into dot patterns is remarkably similar to other printers. Print color is determined by ink color, but multi-color cartridges are available - each primary color with its own set of nozzles and electrical contacts. A broad selection of colors can be created by "dithering" a combination of primary colors from the color cartridge.

In a piezoelectric pump, a ring of piezoelectric ceramic material is built into an ink channel as in Fig. 22-3. When a high-energy electrical pulse is applied across the ceramic ring, its piezoelectric quality causes it to constrict the channel. This causes a sudden displacement of volume that pushes out a single droplet of ink. After the electrical driver pulse passes, ceramic returns to its original shape, and more ink is drawn into the channel to make up the expelled droplet. Piezoelectric ceramic requires short pulses (in the 5 to 10m S range) at high energy levels. Pulse amplitudes can be anywhere from 70 to 200 volts depending on the particular design of the channel and the type of ceramic used. One pump is required per channel, and can fire at rates approaching 5kHz (5,000 droplets per second) - this is one droplet every 200m S.

Bubble pumps (used in "thermal ink jet" or "bubble jet" printers) are also widely used to generate ink droplets. As you see in Fig. 22-4, nozzles and channel construction is very similar to piezoelectric heads, but ceramic rings are replaced by ring heaters. An electrical driver pulse fires a ring heater. In turn, this heats ink in the immediate vicinity. As ink heats, a bubble forms and expands in the channel. When the bubble finally bursts, it ejects an ink droplet, and more ink is drawn in to fill the void. Heated ink droplets also dry faster on paper. Although bubble pumps are fast-working devices, they are limited to firing rates of about 1000 droplets per second. Ring heaters (like dot heaters) require a finite amount of time to cool after firing. If there is not enough cooling time, ink may actually dry out and clog inside the channel. However, bubble pumps do not require nearly as much energy to operate - 24 to 50 volt pulses are typical.

The kind of ink used in drop-on-demand printers is typically an indelible, solvent-based chemical that is resistant to drying in air. As a result, most ink jet heads can be left unattended for prolonged periods of time (often several days to several weeks) without fear of nozzle clogs due to drying. Most ink jet printers also have a type of "ink cap" in the printer's carriage home position that wipes each nozzle whenever the head reaches its home position, and covers them whenever the printer is turned off.

Sooner or later, solvent will evaporate into the air. Evaporation begins to increase the ink viscosity inside each channel - it becomes thicker. In early stages , this can cause ink to sputter or travel off course to the page. In advanced stages, solvent may evaporate entirely, or enough to allow ink to dry and harden in the channel. This is known as a clog. The afflicted nozzle(s) may still fire electrically, but no ink will flow until the clog is cleared. The ink jet head will have to be cleaned or replaced. Clogs may also be dislodged through normal use. Once any viscous ink is forced out through normal use, proper operation will return automatically. In today's ink jet printers, clogs are rare since the head is kept well-covered when not in use.

When ink droplets leave a nozzle, they are still in a liquid form. Once a droplet reaches paper, it must dry almost immediately so that the finished page can be handled. This is not always easy to accomplish if you are using the wrong paper type. Paper must accept ink into its fibers just the right way to dry it quickly, yet leave droplets on the surface for a crisp image. If paper absorbs ink too readily, the dried image may appear light or faint - lacking contrast. If paper does not absorb ink quickly enough, ink may remain a liquid which can run with other colors, or smear and smudge when touched. Ordinary xerography-grade paper is actually too porous for ink jet printers - ink runs and saturates the paper which causes it to bend and buckle. To guarantee just the right drying characteristics, use a specially-made ink jet paper impregnated with clay or solvent-absorbing chemicals that cause ink to dry quickly while leaving a clear, dark image. Ink jet paper is a bit more expensive than ordinary paper, but the results are often worth it (especially when printing dense ink images such as high-resolution or color pictures). The best way to determine the compatibility between paper and ink is to test the printer in actual operation. Either ink or paper may have to be changed to optimize the printer's performance.

Ink jet dot-matrix technology offers a method of "non-contact" printing which can mark a wide variety of surfaces and paper types. Printing speeds rival any impact printer, yet operation is very quiet. Nozzles and ink channels are incredibly small, so dot resolution can be extremely high - often at 300 DPI or more. Ink jet heads have no mechanical parts, so they enjoy high reliability throughout their working life. They stay cooler than impact heads, so do not suffer the pauses and hesitation encountered when impact printers handle complex graphics. Since many commercial print heads are disposable after 200 pages or so, reliability should not be a problem. Ink jet printing has made low-cost color printing available at a surprisingly good quality level. Since ink jet heads require little energy to function, the entire printer assembly can be made much smaller and lighter, so they’re ideal for use with mobile computers.

Unfortunately, ink jet heads are sealed devices. If one ink pump fails, the entire head must be replaced. The ink itself can be a frustrating problem. Ruptured print heads or leaking cartridges can spill thick, indelible ink everywhere. Fabrics and other porous materials are particularly susceptible to permanent stains - even your skin can be stained. Cleaning and purging procedures can be very messy, (which is largely responsible for the tremendous popularity of disposable heads/reservoirs). Ink jet printers in graphics mode are typically slow devices. An output of several pages per minute is considered speedy. The need for specialized paper continues to be a problem, although the formulation of new inks and broad availability of ink jet paper is keeping costs down.

Although individual paper handling mechanisms will vary slightly from manufacturer to manufacturer, ink jet printers use two distinct types; friction feed and tractor feed. Each of these systems operates in a different manner, and suffers from its own unique set of problems.

As its name suggests, a friction feed paper transport uses friction to push paper through the printer. Paper is threaded into the printer along a metal feed guide. The guide ensures that paper is maneuvered properly between the platen and pressure roller(s), then up in front of the print head assembly. A set of small, free-rolling bail rollers press gently against the paper to help keep it flat around the platen. In order to allow the free passage of paper during threading, a lever is often included to separate pressure rollers from the platen. After paper is positioned as desired, the lever can be released to re-apply pressure. From then on, paper can only be moved by hand-turning the platen, or the printer's actual operation.

A paper transport system for a Hewlett-Packard DeskJet printer is shown in Fig. 22-5. High-energy square wave pulses provided by the ECU's motor drive circuits feed a stepping motor. Depending on the quantity of pulses and their sequence, the motor can be made to step clockwise or counterclockwise by any amount. The stepping motor provides force to a drive train of gears. The drive gear (or primary gear) operates a secondary gear attached to the platen. Gear assemblies are usually used, but pulley systems can sometimes be found. In some designs, a stepping motor is used to operate the platen directly (known as direct drive). The drive assembly offers several useful features. First, the use of gears provides a reliable drive train - gears do not stretch or tear with age, and they will not jam or slip as long as they are kept clean and aligned properly. Second, the use of a smaller primary gear provides greater positioning accuracy for the platen.

Friction feed paper transports are relatively simple and elegant devices which are ideally suited for handling single sheets of paper. The greatest problem with friction feed is the tendency for paper to "walk" left or right as it feeds. If the tension provided by the platen and pressure roller(s) is not absolutely even across the length of the page, paper can also twist clockwise or counter-clockwise as it feeds. Walking problems are most frequently found in old printers where the rollers’ surface material has degraded, or in printers where debris has worked its way into the rollers.

Tractor feed does not rely on friction to transport paper. Instead, paper is pulled through the printer. A set of sprocket wheels are mechanically linked to the platen drive train. Pegs on each sprocket wheel mesh perfectly with specially made paper. This type of paper (also called continuous-feed or fan-fold paper) has holes perforated along both sides. Paper is threaded into the printer along a metal feed guide. There is very little resistance from its contact rollers, so paper can easily be fed through and secured into its sprocket wheels. Most sprocket wheels can slide left or right to accommodate a selection of paper widths or tractor feed label products. Bail rollers are included to help keep paper flat against the platen. Once paper is threaded, it can only be advanced by hand-turning the platen knob, or in actual printer operation. Although older ink jet printers used tractor-feed transports (such as the HP QuietJet series), virtually all ink jet printers now use a friction-feed transport which is optimized for stacked single sheets of paper.

Ink jet printers use serial print heads - fully-formed text and graphics are formed by passing a print head left and right across a page surface. As the head moves, it places a series of vertical dots that creates the image. In this way, a complete line of text can be generated in a single pass (letter quality text or graphics may require additional passes). As you might imagine, the process of moving a serial print head becomes a serious concern. It must move at the proper time, at the proper speed, and over the proper distance to within several thousandths of an inch on every pass. The high-resolution graphics available from ink jet printers require even greater positioning precision.

The task of moving a serial print head is handled by the carriage transport. A print head is mounted to a platform or holder (the carriage assembly) as shown in Fig. 22-6. Most serial printers use some type of belt drive. A carriage motor (often a stepping motor used in conjunction with a gear train) drives a primary pulley which is connected to a secondary pulley by a drive linkage. A drive linkage may be a wire, belt, or chain, depending on the weight of the print head and its desired left-right speed (or slew). At one point, the drive linkage is connected at the carriage, which rides along one or more low-friction rails (or carriage rod). Rails keep the carriage rigidly parallel to the platen at all points. When the stepping motor turns counter-clockwise, the carriage assembly slides left, and vice versa.

Positioning precision for a belt drive is determined by the stepping motor's resolution and the pulley diameter. This holds true for a direct drive mechanism. If the primary pulley works through a gear train, that gear ratio must also be included. As an example, suppose a stepping motor directly drives a pulley 1" in diameter. The circumference of the primary pulley would be [pi * d] [3.14 * 1"] 3.14", so one complete motor revolution (thus one complete pulley revolution) would cause the linkage to travel 3.14". If the stepping motor works at 200 steps per revolution, each step would turn the pulley 1/200th of a revolution, or [3.14/200] 0.0157" of linear travel.

Suppose the pulley was only 0.5" in diameter. Its circumference would only be [pi * d] [3.14 * .5"] 1.57", so a single motor rotation would only move the carriage 1.57". At 200 steps per revolution, each step would drive the carriage [1.57/200] 0.0079". Smaller pulleys (or motors with more steps per revolution) can achieve finer positioning - but at the cost of more steps to traverse the platen width.

Ink jet printers tend to be light and economical devices which enjoy a long, reliable working life. However, there are some situations where problems can occur. Trouble usually strikes in the ink head, paper transport, carriage transport, or electronic control unit (ECU). This part of the chapter offers a selection of symptoms and solutions that can help you deal with ink jet failures.

Symptom 22-1. The print quality is poor (dots appear faded or indistinct). Unlike impact printers, the quality and type of paper used in an ink jet system will profoundly impact the print quality. Start by checking your paper supply. Make sure that the paper is well-suited for use in an ink jet printer. Porous papers such as ordinary xerography-grade paper tends to absorb ink quickly and run the ink through its fibers - the result is typically a dull, faded appearance. This can also happen if the paper has an unusual or chemically-coated surface.

If the paper is correct, suspect the print head next. In many cases, light or poorly formed dots can occur as the disposable print cartridge nears exhaustion. The print head may also be dirty - accumulations of dust or debris can eventually block the print head nozzles. Although a typical ink jet printer routinely cleans a print head, an old or worn cleaning surface may no longer provide sufficient cleaning. If the cleaning pad is worn or missing, it should be replaced. If the problem persists, try a new print head (typically a single head/reservoir assembly that can be replaced in a matter of seconds).

If problems continue, there is probably a fault in the printer's driver circuitry - if signals are not strong enough to fire the head's piezo or bubble pumps correctly, print will easily be distorted. Review the Hewlett-Packard DeskJet assembly of Fig. 22-7. You will notice that there are three main boards in the printer; the logic board (ECU), the driver board and the power supply. Chances are that one or more elements in the head driver circuit or power supply has become defective. Before replacing anything, check the power supply outputs. If any of the outputs are low or missing, replace the power supply. If all power outputs are correct, the fault is probably in the driver board, so try a new driver board. In some ink jet printer designs, the power supply, driver circuits, and main logic are all assembled on the same PC board. In that case, simply replace the entire ECU outright. Figure 22-8 illustrates the various functions performed by the main logic and driver boards.

Symptom 22-2. Print has one or more missing dots that resemble "white" lines. This also takes place during a self test. It seems as if one or more of the print head's nozzles will not fire. Always start by suspecting the print head - if a nozzle has jammed from accumulations of dust or debris, it can shut down the nozzle. Make sure that the print head is clean. Normally, ink jet printers wipe the print head every certain number of passes. However, you can remove the cartridge and wipe it with a clean lint-free swab. Also wipe the electrical contacts to ensure a good connection. Replace the cartridge and try the printer again. If the problem persists, try another print head. If a new print head does not resolve the problem, your fault lies almost certainly with the print head driver board. If a driver circuit fails, the corresponding nozzle will not fire. Try another drive board.

Symptom 22-3. Printer does not print under computer control. Operation appears correct in self-test mode. Before you attempt to disassemble the printer, take a moment to check its "on-line" status. There is almost always an indicator on the control panel which is lit when the printer is selected. If the printer is not selected (on-line), then it will not receive information from the computer - even if everything is working correctly.

A printer can be off-line for several reasons. Paper may have run out, in which case you will often have to re-select the printer explicitly after paper is replenished. Even the simplest printers offer a variety of options that are selectable through the keyboard (i.e. font style, character pitch, line width, etc.). However, you must often go off-line in order to manipulate those functions, then re-select the printer when done. You may have selected a function incorrectly, or forgotten to re-select the printer after changing modes. Also consider software compatibility. If you are using a "canned" software package, make sure that its printer driver settings are configured properly for your particular printer. If you are working through Windows, make sure that the proper Windows driver is selected.

Check your communication interface cable next. It may have become loose or unattached at either the printer or computer end. If this is a new or untested cable, make sure that it is wired correctly for your particular interface (i.e. serial or parallel). An interface cable that is prone to bending or flexing may have developed a faulty connection, so disconnect the cable at both ends and use your multimeter to check cable continuity. If this is a new, home-made cable assembly, double check its construction against your printer and computer interface diagrams. Try a different cable.

Double-check the printer's dip switch settings or set-up configuration. Dip switches are often included in the printer to select certain optional functions such as serial communication format, character sets, default character pitch, or automatic line feed. If you are installing a new printer, or you have changed the switches to alter an operating mode, it may be a faulty or invalid condition. Dip switches also tend to become unreliable after many switch cycles. If you suspect an intermittent dip switch, rock it back and forth several times, then re-test the printer. If everything else checks out up to this point, try replacing the ECU board.

Symptom 22-4. Print head moves back and forth but does not print - or prints only intermittently. This also takes place during a self-test. When the printer carriage moves, but print is absent (or intermittent) check your print head first. The ink jet head may simply be out of ink. Try a new ink jet head with a fresh ink supply. If problems continue, check the ribbon cable between the driver circuit and print head. Intermittent connections in the print head or print head cable can lead to highly erratic head operation. A complete cable break can shut down the print head entirely, especially if the break occurs in a common (ground) conductor. Turn off and unplug the printer, then use your multimeter to check continuity across each cable conductor. You may have to disconnect the cable at one end to prevent false readings. Replace any print head cable that appears defective.

There may be a problem with the print head driver supply voltage(s). Use your multimeter to check each output from the power supply. If you find that one or more power supply voltage(s) are low or erratic, you can attempt to troubleshoot the supply, or replace the supply outright. When power supply outputs measure correctly, the fault is probably located in the print head driver board. Replace the driver board. Keep in mind that when the power supply, driver circuits, and main logic are integrated on the same board, the entire ECU will have to be replaced.

Symptom 22-5. The paper advance does not function, or functions only intermittently. All other functions check properly. When a paper advance fails to work at all, begin by observing the paper feed drive train assembly. Check any pulleys or gears to ensure that all parts are meshed evenly and are able to move freely. You can watch this by turning the platen knob located outside of the printer. If there is no manual platen, you can run a form feed. Remove any foreign objects or obstructions that may be jamming the drive train. NEVER try to force a drive train that does not turn freely! Realign any parts that appear to be slipping or mis-aligned. Replace any damaged mechanical parts or assemblies.

Turn off all printer power and examine the electrical connections for your paper advance motor. Make sure that all connectors are installed and seated properly. If you suspect a faulty wiring connection, turn off printer power and use your multimeter to measure continuity across any suspicious wires. It may be necessary to disconnect the cable from at least one end to prevent false continuity readings. Replace any faulty wiring.

If everything checks properly up to this point, either the motor or ECU has failed. With printer power still off and the motor disconnected from the ECU, use your multimeter to measure the continuity of each motor winding. This is not difficult, but you will need to check the schematic of your particular printer for specific pin numbers and resistance measurements. A working motor winding exhibits between 4 to 40 ohms. If you read a short circuit (about 0 ohms), or an open circuit (substantial or infinite resistance), the paper advance motor is probably defective and should be replaced. If you can not determine the location of each motor winding, try replacing the paper advance motor.

If the motor checks out (or a new motor fails to resolve the problem), a fault has likely developed in the ECU. One or more of the motor drive circuits has failed, or the motor voltage output from the power supply has failed. Replace the ECU outright.

Symptom 22-6. Paper slips or "walks" around the platen in friction-feed operation. Friction feed paper transports are only designed to work with certain types of paper - brands within a certain range of thickness and weight. Very fine (light bond) paper or very heavy (i.e. card stock) paper will probably not advance properly. Smooth-coated papers will also probably not work well. Check the specifications for your particular printer to find its optimum paper type. If you find that you are using an unusual type of paper, try the printer using ink jet paper.

Keep in mind that friction-feed was intended for single-sheet operation. Some small amount of walking is natural, but feeding extremely long lengths of paper may result in noticeable walking. It is possible to use continuous-feed paper in a friction-feed transport, but you should expect to see a certain amount of walking eventually - if you have the option, try to stay with single sheets.

If the problem persists, take careful note of each roller condition. An even, consistent paper feed depends on firm roller pressure applied evenly across its entire length. Rollers that are very dirty, or old and dry, may no longer be applying force evenly. Clean and rejuvenate your rollers with a good-quality rubber cleaning compound such as "Kleen-a-Platen" available from almost any comprehensive office supply store.

NOTE: Rubber cleaning compounds can be dangerous, and may not be compatible with all types of synthetic roller materials - read instructions on the chemical container carefully, and follow ALL safety and ventilation instructions.

Old rollers may also be out of alignment. Mechanical wear on shafts and bushings (or bearings) can allow some rollers to "float" around in the printer. Carefully examine the condition of each roller shaft. Ideally, each shaft should be fixed firmly within its assembly, so you should feel little or no "slack". If you feel or see a roller move within its assembly, replace its bushings, bearing, or shaft. Newer mechanical assemblies make it easier to simply replace the entire transport outright. Some pressure roller assemblies can be adjusted slightly to alter their contact force. If your particular printer uses non-adjustable pressure rollers, there is little more to be done (other than replace the mechanical assembly). If you can adjust roller force (using spring tension or a screw adjustment), do so ONLY as a last resort -- and only then in small increments. Careless adjustment can easily worsen the problem.

Check your paper path for any debris or obstructions that may be catching part of the paper. A crumpled corner of paper jammed in the paper path or caught in the feed guide can easily interfere with subsequent sheets. Adhesive label fragments are even more troublesome. Remove all obstructions being careful not to mark any of the rollers. A straightened paper clip can often get into spaces that your fingers and tools will not. Use your needlenose pliers to put a small hook in the wire's end for grabbing and pulling the obstruction. Do not disassemble the roller assemblies unless absolutely necessary.

Symptom 22-7. The carriage advance does not function or functions only intermittently. All other functions check properly. During printer initialization, the carriage is taken to its "home" position. Since the printer has no way of knowing where its carriage is when it is first turned on, finding the carriage "home" gives the ECU physical evidence of an actual carriage position. Under normal circumstances, the ECU will initialize the carriage to the left side of the printer, although "inverted" printers such as Hewlett-Packard's DeskJet initialize the print head at the right. A mechanical or optical "home" sensor will inform the ECU when home is reached. At that point, the exact carriage position is known for certain. As the carriage moves, pulses generated from an optical position encoder confirm that the carriage is in motion.

When the carriage fails to move (or moves only intermittently), suspect a serious mechanical problem. Watch your carriage advance motor and drive train assembly while the printer initializes. A slipping belt or mis-aligned gear may have to be tightened or replaced. Make sure the primary pulley is attached securely to its drive shaft. Also examine the drive linkage to be sure that it is properly attached to the carriage. Replace any parts that are broken or excessively worn. Remove any obstructions or foreign objects that may interfere with the drive train.

If you see that the carriage advance motor does not turn, turn off and unplug the printer, then check all electrical connections to the motor. Make sure that all connectors are installed properly and firmly seated. Use your multimeter to check continuity across any suspicious wiring. When checking continuity, it may be necessary to disconnect the wire or cable at one end to prevent false readings. Replace any faulty wiring.

If everything checks properly up to this point, either the motor or ECU has failed. With printer power still off and the motor disconnected from the ECU, use your multimeter to measure the continuity of each motor winding. This is not difficult, but you will need to check the schematic of your particular printer for specific pin numbers and resistance measurements. A working motor winding exhibits between 4 to 40 ohms. If you read a short circuit (about 0 ohms), or an open circuit (substantial or infinite resistance), the paper advance motor is probably defective and should be replaced. If you can not determine the location of each motor winding, try replacing the paper advance motor.

If the motor checks out (or a new motor fails to resolve the problem), a fault has likely developed in the ECU. One or more of the motor drive circuits has failed, or the motor voltage output from the power supply has failed. Replace the ECU outright.

Symptom 22-8. The carriage operates, but it does not always position properly. Improper carriage positioning can take many forms - character spacing may be erratic, or the carriage may sometimes ram into the left or right side frames. Faulty mechanics are often at the heart of carriage problems. Turn off and unplug the printer, then inspect the carriage drive train very carefully. Pay particular attention to the drive linkage to be sure that it is reasonably tight (Fig. 22-9). One or both pulleys may be loose. Inspect any drive gears between the motor and primary pulley for signs of slipping or broken gear teeth. Replace any parts that appear broken or excessively worn.

An optical encoder provides pulses to the ECU as a carriage moves. The pulses allow the printer to position its carriage. Erratic or inconsistent positioning may be the fault of the encoder. Try replacing the encoder. If the problem persists, there is probably a logic fault in the ECU. Replace the ECU outright.

Symptom 22-9. The printer only prints 1/2 or 3/4 of the page. Chances are that your PC is not using the correct parallel port mode for the printer. For example, Compaq PCs often experience parallel port compatibility problems with Canon ink jet printers. There are generally three resolutions for this kind of problem. First, you can try setting the PC’s parallel port to ECP:

• Boot Windows 95 and right-click on the My Computer icon.
• Select Properties and select the Device Manager tab.
• Double-click on Ports (COM & LPT).
• Double-click on ECP Printer port (LPT1). If your configuration is already Printer Port, this correction does not apply.
• Select the Driver tab, choose Change Driver, then select "Show all devices".
• Under Models, select Printer port, then click OK.
• Click OK again.
• Shut down Windows 95 and reboot.

Next, you should check that the LPT port is using the correct resource settings:

• Boot Windows 95 and right-click on the My Computer icon.
• Select Properties and select the Device Manager tab.
• Double-click on Ports (COM & LPT).
• Double-click LPT, then select the Resources tab.
• De-select Automatic Settings.
• Change the Basic Configuration, find the configuration that meets the following conditions:

1. Input/Output Range 0378-037?
1. Input/Output Range 0778-077?
1. Interrupt Request (IRQ) 07
1. NO DMA

• Select OK.
• Shut down Windows 95 and reboot.

If the characters "[K" are printed at top of page, and the rest of the page is correct, you may need to update your drivers:

• Boot Windows 95 and right-click on the My Computer icon.
• Select Properties and select the Device Manager tab.
• Double-click on Ports (COM & LPT).
• Double-click LPT, then select the Driver tab.
• Look at the File Revision line, LPT.VXD v4.00.950 - replace LPT.VXD v4.00.950 with LPT.VXD v4.00.503 (the LPT.VXD file is located in the Windows\System directory).
• Confirm that your port is set to "Standard Bi-directional" in the CMOS Setup.

Symptom 22-10. The power light blinks continuously, or you hear 3 beeps. The ink cartridge may not move, or may remain in the middle of the carriage. In virtually every case, the ink cartridge is not seated in its holder properly, and is not making the necessary electrical connections. Simply remove and reinstall the ink cartridge.

Symptom 22-11. You replace an ink cartridge, but the cartridge refuses to print. Chances are that you forgot to remove the small piece of colored tape (usually orange or blue) covering the ink nozzles. Remove the ink cartridge, remove the protective tape, reinstall the cartridge carefully, then retry the printer.

Symptom 22-12. You encounter "Out of memory" errors when attempting to print. There are a number of very real possibilities which can result in memory errors. Make sure that your current printer is, in fact, configured as the default printer. Try closing down all unneeded or background programs. Next, try reducing the printer’s resolution (i.e. from 720x360 to 360x360), or try the printer in "draft" mode. If you’re printing a multi-page document (especially a complex document), try printing only 1 or 2 pages at a time. Also make sure that there is plenty of free hard drive space on the drive containing your /Temp directory - complex images may require 50MB or more of free hard drive space for temporary printing files. As a last resort, you might also try reducing the video resolution to 640x480.

Symptom 22-13. The color printed image does not match the image on the monitor. There are several reasons for this. You must always realize that a perfect match is not always possible because of the differences in monitor technology (and color balance), as well as overlooked factors such as the amount of ambient lighting in the room. If a good color match is possible, you should suspect the color ink cartridge first. Try a printer self-test and verify that all ink colors are available. Make sure that the color ink cartridge is fresh, and try a cleaning procedure to ensure that the ink nozzles are clear. Low or obstructed ink supplies will impair proper color mixing, and result in poor color reproduction.

You might also consider upgrading the video display driver. Since the printer’s driver receives its information from the video driver, a poorly-written video driver may actually impair the printer’s color reproduction. Try printing from a different software application - some applications provide better color matching support than others. High-end graphics programs (i.e. CorelDraw) tend to support color matching better than low-end utilities like Microsoft Paint. Finally, try configuring Windows for color matching:

1. Click on Start, select Settings, then click on Printers.
1. Right click on your desired printer.
1. Select Properties from the menu.
1. Click on the Graphics & Color tab.
1. For Color Mode, select "Auto-Adjust Color".
1. For Halftoning, select "Smooth".
1. Click on the OK button and try printing again.

Symptom 22-14. The printer does not work when daisy chained from another parallel port device. This often happens with parallel port scanners, tape drive, Zip drives, and other popular parallel port devices. Most current ink jet printers have a bi-directional communication feature. This feature does not share the parallel port, and causes intermittent problems with some parallel port devices. You can correct this problem by downloading and installing upgraded printer drivers from the printer manufacturer.

That finishes Chapter 22. Be sure to review the glossary and chapter questions on the accompanying CD. If you have access to the Internet, take a look at some of the ink jet printer manufacturers listed below:

Canon: http://www.ccsi.canon.com/

Epson: http://www.epson.com

Hewlett-Packard: http://www.hp.com

Olivetti Lexicon: http://www.olivettilexikon.com/