Printer and Photocopier Troubleshooting and Repair Collection

Version 2.48

Copyright © 1996-2001
Samuel M. Goldwasser
--- All Rights Reserved ---

For corrections/comments/suggestions, please contact me via the Sci.Electronics.Repair FAQ Email Links Page.


Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:
  1. This notice is included in its entirety at the beginning.
  2. There is no charge except to cover the costs of copying.



Table of Contents



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    Preface

    Author and Copyright

    Author: Samuel M. Goldwasser

    For corrections/comments/suggestions, please contact me via the Sci.Electronics.Repair FAQ Email Links Page.

    Copyright © 1994-2001
    All Rights Reserved

    Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:

    1. This notice is included in its entirety at the beginning.
    2. There is no charge except to cover the costs of copying.

    DISCLAIMER

    Some of the procedures described in this document require access to dangerous voltages, hazardous laser radiation, moving mechanical parts, and other potential risks to personal safety and damage to equipment and property. The authors and contributors to this document will not be held responsible for any direct or collateral damage which might result from following the suggestions or recommendations contained herein including but not limited to: shock, burns, electrocution, vaporization, meltdowns, torn flesh, destruction of the equipment, and local or planetary wide power disruptions or implosions.



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    Introduction

    Most of the articles in this document have been compiled over the last few months from postings on the USENET newsgroup sci.electronics.repair. I cannot vouch for the accuracy of all of the recommendations they contain but have edited out anything I felt was totally bogus. I apologize if your response is not here - it could have been that I missed the posting and will welcome contributions.

    Note that many of the problems and solutions are listed with respect to specific models. Even though your model and problem may not be included, there is a good chance your problem is covered but with respect to some other model printer or copier. Therefore, search for a generic description of the symptoms and you may get lucky.

    Since the operation of laser printers and photocopiers is very similar, check both chapters to see if your problem is covered when dealing with either type equipment.

    There is also a chapter on fax machine problems though it is pretty sparse at the moment.

    Eventually, this document may be expanded into a full "Notes on the Troubleshooting and Repair of Printers and Photocopiers". For now, be happy that it exists at all! :-)

    As always, comments, suggestions, and corrections are welcome.

    See the document: Troubleshooting and Repair of Consumer Electronics Equipment for general information on tools, test equipment, tips, techniques, and much more.

    SAFETY

    Also see the document: Safety Guidelines for High Voltage and/or Line Powered Equipment.

    While printers are not generally considered dangerous pieces of equipment (compared to TV, monitors, and microwave ovens, at least), some types - laser printers in particular - present a variety of hazards that should not be underestimated. In addition, photocopiers - particularly larger high speed machines - need to be treated with great respect while servicing.

    There are minimal dangers in servicing most printers. However, there may be exposed line voltage near the line cord and long hair or neck-ties may be sucked in along with paper! Laser printers have their lasers but these are generally located such that accidental exposure to the beam is minimized. The toner in copiers, plain paper faxes, and laser printers may be harmful if inhaled and is a potential fire/explosion risk if carelessly vacuumed. Each of these possible safety issues is discussed below with additional specific information in the chapters for the equipment to which it applies. All in all, working on printers is relatively low risk.

    The first set of items applies to all line operated printers:

    The following apply to laser printers and photocopiers:

    And finally, for laser printers and laser photocopiers:



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    Printer and Photocopier Technology

    Dot matrix printer operation

    These are the only type of impact printers still in wide use. A set of steel pins - typically between 9 and 24 - strikes the paper through a fabric or carbon film ribbon. The pins are activated by solenoids which are controlled by the printer's control logic. Multiple passes may be used to increase the effective number of pins and improve print quality (letter versus draft mode).

    For text, an internal character generator (ROM) converts ASCII codes to pin firing patterns. For arbitrary graphics, the actual bit map is read out and used to control the pin drive.

    The paper, carriage, and sometimes ribbon movement use stepper motors. These, their drivers, or interconnect cables, are common problem areas.

    Daisy wheel printer operation

    These may still turn up at yard sales and flea markets but have virtually disappeared due to slow speed and limited flexibility with respect to graphics. In their defense, for basic text, their quality is superb for a low cost printer.

    Instead of pins, these use a wheel with all the possible characters molded on 'leaves' around the perimeter. The wheel spins to the correct character position and a hammer than taps the leaf to impress the character (via a ribbon) on the paper. Carriage and printhead movement is similar to that of dot matrix printers.

    (From: Peter (hedgieus@yahoo.com).)

    Some history/trivia:

    The daisy wheel printer (interestingly) was patented before World War II! It was GE or a GE engineer, but only commercialized by Diablo, which was later bought by Xerox in its expansion to California. Later spinoff was Qume, and then lot of companies got into it, some Japanese, some local (California). Daisy wheel technology was killed by the laser printer becoming cheap and having better quality. Original impetus for it was speed: IBM Selectric was able to print at 10 char/s (good for 110 baud modems!). It moved the whole ball (big inertia). Daisy wheel only moves one spoke, (to print one character) and got 30 chars/s.

    Near the end of the era, 'on the fly' printers got as fast as 80 char/sec.

    Ink-jet printer basics

    (From: Tony Hardman (AHED_CIJ@f54x19.demon.co.uk).)

    There is a US publication called 'The Hard Copy OBSERVER' from Lyra Research Inc. Tel: (617) 322-0708.

    This discusses the latest technologies and who does what. It may not cover the print head technology very much but is a good read if you are into print technology in general.

    There are many companies that sell variable print processes. One I have heard of is RALFLATAC. They do a brochure that does an excellent brief of most technologies available for printing. They have UK (and many other sites in europe) and US sites. UK Tel 01732-583661, US Tel (704) 684-3931.

    I have no idea if you can easily get copies of either publication from them so here goes a very very brief description.

    Ink jet printing has two main types, continuous ink jet (CIJ) and impulse printing (DOD) (drop on demand). Each of these can be a single jet, or an array of jets.

    A primer on priming

    The priming station of a typical ink-jet printer (e.g., HP DeskJet 500C) includes a rubber seal ('boot') and small pump to actually suck on the end of the print cartridge to free up nozzles (there are 50 or more in a typical print cartridge) that have dried up or become clogged. It may fire all the nozzles at some point during this process as well. It also includes rubber 'flappers' which the end of the cartridge pass over to wipe off excess ink.

    Priming and cleaning are normally done automatically upon power-on and possibly between pages. However, additional cycles may be needed at times.

    With the water based ink, even if the printer is powered off properly which seats the cartridge(s) on a rubber seal, some evaporation occurs so priming will often be needed after it sits idle for a while. Note: Don't kill power to an ink-jet printer as soon as your printout pops free - it needs to position the printhead and cartridge(s) on the rubber boots. Wait until the printhead stops moving and clunking. Some (older) printers don't even have a seal in which case letting it sit idle is even more likely to result in problems.

    If there has been ink spilled into the priming area, it may clog up the little hose connecting the priming station to the pump - I have used a wooden toothpick to clear the hole though this may be risky if it should break off. With care, a wire rounded off at the end so as not to puncture the tubing can also be used. Complete disassembly and washing of the parts is probably the best but is probably a pain.

    A bit of ink-jet history?

    (From: John Nagle (nagle@netcom.com).)

    The original ink jet printer of this type was the Teletype Inktronic, which introduced the concept of video-type distortions to printing. It appeared around 1970, and was so bad nobody tried again for years.

    (From: Tony Hardman (AHED_CIJ@f54x19.demon.co.uk).)

    I guess that is why it was used in industrial applications I guess. Were the 'video-type distortions' a deliberate feature or just a coincidence of how they turned out?

    Who are/were Inktronic???(apologies to anyone connected with them) I guess that may have been spin off development from some work contracted out by IBM, but it was so....?? (costly/low res/unreliable - choose one) they lost interest. Although one of the very early machines still runs well on a textile mill. It had a large number of jets side by side, and may be multi color too. I've only seen the patents so don't know exactly what it looks like.

    I thought original ink jet printer was a chart recorder developed in the last century. It was just a nozzle on deflection mechanism, and was not modulated so it was always printing. It was a lighter mechanism than actually trying to move a pen and so had some performance advantages over other technology available at the time...

    The same reason CIJ still sells world wide, even when high resolution DOD is biting at its heals.

    Inkjet types (at least from a Xerox perspective)

    (From: Peter (hedgieus@yahoo.com).)

    Here are history/trivia. (I used to work at Xerox marking technology group, working on ink-jets and daisy printers.)

    Response times of resistance heater elements in ink jet printers

    The ink drops that make up the 'image' on the paper from an ink jet printer are expelled by microscopic resistance (thin film or the like) heaters with response times in the 10s of microseconds if I recall correctly. When living in the macro world, it is often counterintuitive to realize that a resistance element can have such a fast thermal response.

    (From: John Eaton (johne@vcd.hp.com).)

    The trick is that a lot of the energy that you pump into the resistor leaves the printhead with the fired dot. One way to detect Out_of_Ink is to mount a thermistor on the printhead and watch for a sudden rise in temperature as you are firing.

    How many colors can an ink-jet printer can produce?

    "I use a HP680C in the office, and it have two cartridges, one for black and one for color (yellow/cian/magenta?). If the printer fire one drop of each ink at a given point, we can have only 6 different colors (ignoring white and black). If it can fire two or more drops at a given point, maybe we can have more colors, but I suspect that the printer use this to control quality of the presentation, not the number of colors. Anybody knows for sure? With dithering it can make more colors, with reduced resolution."

    Like most print processes you only have a limited selection of inks to use. Full colour can be derived from three primary colors, just like a monitor. For monitors, these are Red, Green, and Blue because monitors emit light resulting in an additive color process. Inks, on the other hand, absorb light so printing is a subtractive process. The resulting inks should then be cyan (blue+green or -red), magenta (red+blue or -green), and yellow (red+green or -blue).

    Therefore, the colors used in common ink-jet printers are not really capable of producing true full spectrum photorealistic quality results since they are red (not magenta), blue (not cyan), and yellow. These are optimized for nice saturated primary colors when used independently. Also see the section: Why are red, blue, and yellow inkjet primaries?.

    In addition, the combination of the three primary colors should be capable of being combined to produce black but due to misregistration and the pigments used, this black would be somewhat muddy and brown. Therefore, a separate black ink cartridge is normally used for black printing.

    (From: Tony Hardman (AHED_CIJ@f54x19.demon.co.uk).)

    With printing there are more problems than solutions and I do not know which method HP use in their printing.

    If you can vary the drop size, you can change the drop spread on the paper. This can be done by firing bigger slugs of ink, or multiples of the drop at the same position. As you can figure the ink will either spread and make a bigger drop, or stay the same size and become denser. Depending on the resolution you want these could both improve colour density. This depends on two key components.. The ink, and the paper.

    The problems with laying down multiple drops on paper is that if you do a large block the paper will curl up and the overall image becomes worse. This is why you can pay 1$ a sheet for 'quality' paper.

    Another problem with this is speed. Firing two drops in the exact same place is difficult... Unless the head is stationary but that is not good either. You may notice that most DOD printers in high resolution mode do a number of passes over the same place. This does allow dithering and other techniques for resolution / colour enhancement. They usually only print while going in one direction for improved mechanical control.

    In the 1600 printer there is a heater to assist with the drying times and reduce the curling problem.

    Inks are a problem too. They can dry at different times because of the different dyes used, or they may not mix how you expect if you place two colours on top of each other. Its only ink ... but to get the best balance of surface tension, drying time, viscosity, colour, stability.... and more is not as straight forward as it might seam. I have noticed that the water based inks are improving, and there are some that do not run if they get wet (after drying on the paper).

    I think the spec in your manual may suggest what method they use.. The printer resolution (best) is 600dpi (I guess), and I recon the best full colour resolution is lower. Also the print head is only 300dpi so you must do two passes to get 600dpi black (single black ink cartridge). This suggests a partial step of 1/600 inch between the passes. What happens when you print black using the colour head? How many passes, how much slower? The resolutions quoted may also be 600 * 300, or what ever. If they make blocks of colour from a potential 600dpi machine, the resultant image is probably only 75dpi (possibly less). This still might be called 600dpi, because the drop placement uses this resolution, but it is not 600dpi at full colour. The resolution of quality picturers / poster is several thousand dpi, but not a variable image (not ink jet).

    In the Lyra publications they did publish the real print head specifications for the machines they review. They also include some of the methods of colour printing.

    After all this I have noticed that I have not answered the question of how do HP et all get their colour resolutions. All I have mentioned is a few of the parameters that the designers have to deal with.

    Why are red, blue, and yellow inkjet primaries?

    For a subtractive printing process, the 'optimum' primary colors for a 3-ink system would be closer to magenta, cyan, and yellow. However, these are not generally used. Why?

    I don't know the precise answer but it is no doubt a tradeoff between cost and which colors are used most often. For non-photo printing, the straight red, blue, and yellow are far more useful since they can be use by themselves or in simple combination to produce a wide range of vibrant, if not realistic colors. For example, pure red is far more likely to be used for simple graphics than magenta. To make something that looks like pure red using magenta and yellow requires a precise combination - not easy to do with an inkjet printer!

    About inkjet printer ink

    No, you can't refill your HP DeskJet cartridges with fountain pen ink!

    (The following is from someone who also sells inkjet refill kits so this may not be an entirely unbiased writeup.)

    (From: John Connolly (toner@idirect.com).)

    There are at least 10 ingredients in inkjet ink, starting with triple distilled, de-ionized water, dye or pigment color of a known particle size, humectants such as glycol to minimize evaporation (and head clogging), surfactants to balance the surface tension and paper wetting, resins to get good paper adhesion, biocides and fungicides and buffering agents for the correct pH. These considerations ensure that properly reverse engineered inks not only work, but produce a print comparable to the OEM. For printers like Epson, with fixed permanent print heads in the printer, expensive repairs are also avoided.

    To make matters worse HP has rigged their most popular black cartridges for the Deskjet 500 & 600 series to curb refilling, with air bladders, constantly changing maze/ venting assemblies at the bottom, and logic to change the signals to the micro-resistor jets on the 3rd or subsequent reinstallation of the cartridge. The color cartridges for these MUST be refilled before air locks occur, particularly in the yellow chamber.

    Some people still manage to get an acceptable refilling success rate with these Deskjets, but we feel it is a bad introduction to refilling for the first time refiller. Deskjet series 700, 800 & 900 are better bets to refill.

    But, the current Lexmark, Canon, Xerox and Epson cartridges are by far the easiest to refill.

    Image Control's refill kits for the Canon 4000 series refill the BCI-21 black 40 times, or the BCI-21, 12 times EACH color.

    More details on inkjet inks, a description of our refill kits which are larger than most offered, references and printer/cartridge tips are available at Image Control's Web Site.

    Laser printer and photocopier operation

    Copiers and laser printers have a lot in common. The major difference is in how the image is formed on a photosensitive drum:

    Beyond this, copiers and laser printers are nearly identical (at least in principle) except that copiers use a positive process (dark areas in the original result in marks on the paper) and laser printers commonly use a negative process (a spot of light results in a dark mark on the paper).

    The most sophisticated machines are now actually scanner-laser printer combinations with buffer memory so that multiple copies can be made without rescanning the original, sorting and collating is more flexible, scaling and rotation can be done digitally, and other features not possible with simple copiers.

    (Portions from: Copenhagen Cowboy (cowboy@fastlane.net).)

    The photosensitive drum is the heart of the laser printer or copier. In larger machines, it may be a separately replaceable unit. In most laser printers and smaller copiers, it is part of the 'toner cartridge' and is a throw-away (or may be recycled).

    The drum is coated with a photosensitive material which has an extremely high resistance when in darkness. It's resistance drops to a low value when illuminated.

    All of the following takes place as a continuous process as the drum rotates. Note that the actual photosensitive drum in most copiers and laser printers has a circumference that is much smaller than the length of the printed page. Therefore, only a portion fits at any given time and the charging, exposure, transfer to the paper, cleaning, and erasing is a continuous process:

    That is the basic process. Many variations are possible and depending upon the machine and manufacturer, some of this may be a little different. Where a (disposable) toner cartridge is used, many of these components are replaced with the cartridge - typically the drum, toner itself and developer (usually combined into a single powder), developer magnet (really neat!), cleaning blades, some of the corona wires.

    There is also some photocopier information at:

    Laser printer operation summary

    (Portions from: Zaki (zg@ix.netcom.com).)

    In general the principle of electrostatic laser printing is as follows:

    1. Charging a photoconductive selenium (or other) coated drum.

    2. Discharging the drum with the laser steering engine in accordance with the input image rasterized pattern. (the laser is modulated to generate a predefined pixel pattern on the face of the drum - the focal plane).

    3. The rotating drum attracts toner to the charged pattern (latent image) generated by the laser.

    4. The toner is transfered from the drum to the moving papaer to generate a full image.

    5. The paper carrying the toner moves through the heater to fuse the toner to a fine non-erasable image.

    The laser steering engine is combined of the following components:

    Cleaning and Handling of Photosensitive Drums

    Where the drum is located inside a replaceable toner cartridge, there is no need for special handling. However, where the drum is a separate unit, the following applies. Or, if for some reason, you need to disassemble (gasp!) a cartridge:

    (From: David Kuhajda (dkuhajda@locl.net).)

    Whatever you do, do NOT use alcohol on an organically based drum, it will ruin it. The alcohol causes the material to crystalize. I use to do copier service and this was stressed a lot by the manufacture as they switched from the old selenium drums to the new opc drums. Direct sunlight will immediately destroy the drum. A couple of minutes under normal lighting is no problem, just place it in a dark area and put a black cloth over the top of the drum while it is out. If you are replacing the drum cleaning blade or cleaning the crud off the blade, make sure you powder up the drum completely and the blade before reapplying power. The toner actually is a slight lubricant and the rubber cleaning blade directly on the drum will also ruin it. Just print a few low text copies after reassembling to allow the blade to reseat properly.

    (From: hapticz@email.msn.com.)

    Short periods (less than 5 min) under fluorescent lighting is safe.

    Direct sunlight kills them immediately.

    Just have a clean brown paper bag to shove it into while it sits on the table outside the machine.

    Often more damage is done to them physically during insertion/removal. just be careful.

    Xerox used to clean the 10" diameter drums with 90% isopropyl alcohol and some kind of "Kim Wipes" in our office, that was years ago though.

    Book on laser printer maintenance and rapair

    (From: Michael (ncacaver@aol.com).)

    Get the book: "Easy Laser Printer Maintenance and Repair by Stephen J. Bigelow".

    Your local library should have it or be able to get it. Stephen J. Bigelow has several other books on printer repair, both laser and non laser types. All are very good.

    Discussion on laser diodes in laser printers

    "I just acquired the optics from a dead laser printer and have been trying to understand it. There are two functions I have yet to grasp. One is something which it has but for which I see no need. There seems to be a heater (Contains mica) and a thermometer, with PCB markings like "T1" and H2" or something similar. If these the laser is temperature controlled, why? There seems to be a control photodetector to monitor the laser diode so temperature control appears like overkill unless the photodiode itself has too much temperature dependence and the drum exposure is very critical."

    (From: Jonathan M. Elson (jmelson@artsci.wustl.edu).)

    There is a heater inside the fuser roller. This is what melts the toner into the paper. It is thermostatically controlled, and then has a safety thermostat in case the control fails.

    There are two photodetectors for the laser. One compensates for dimming of the laser over years of use, the other picks up the beam at a particular angle of the polygon mirror, and synchronizes the raster electronics to the polygon rotation.

    "The other thing is something I cannot find, the aperture defining the nice well-formed pixel. So far I must admit the study has been a bit superficial but the aperture ought to be pretty obvious if there is one!"

    The laser is the aperture. With an optical path of 0.5 m or so, the laser is a pretty good approximation of a true point source. A simple lens makes it look like a very good point source.

    "Finally, how are the correction lens made? They look like slices out of the middle of some fair sized lenses, but that would be a very wasteful way to make them. Can they be diamond formed to nearly the final shape and with such good finish so only a simple polish completes them. Grinding the old-fashioned way on a sliver of glass looks doomed to generating all sorts of defective approximations to a sphere. (As far as I can tell they are glass, or some wonderfully hard plastic I would like to know more about!) Can they be molded to sufficient precision? (The sides are ground or sawn.) Thanks to anyone who can bring me up to date on lens fabrication technique."

    I think they mold these lenses to near correct shape, then grind and polish to the desired aspheric shape with specialty machines for that purpose. (Note that almost all eyeglasses are aspheric for astigmatism correction.) Yes, these lenses are glass, I've had a few printers apart myself.

    Types of toner

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    There are two basic kinds of toner: magnetic and non-magnetic. If your laser printer has a Cannon 'engine' it most likely uses magnetic. NEVER use the wrong type. The imaging process is extremely delicate and specific toners are important. Use of toner that is slightly different could result in all black or all white copies.

    So you put in the wrong type of toner?

    "I have a 3M Model 6312 copier. I believe it is a re-badged Lanier. I didn't pay much for it but it worked well. When the toner warning light came on, I made the mistake of adding the wrong kind of toner. I removed the wrong toner as much as I could by vacuum. Is there anything I should do before adding the right type of toner? Did I do serious damage to the system? What to do if the warning light remained on even with the right type of toner added? Any suggestion will be greatly appreciated."

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    If your copier uses non-magnetic toner, it is mixed with iron powder, called the Developer. Both have to be removed and all residue vacuumed out. If the copier uses magnetic toner, less of it will remain in the machine. Try to get as much as possible out. Do not scratch the roller on which the toner sits.

    WARNING: See the section: Warnings about vacuuming laser printer toner before using a household vacuum cleaner to do this!



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    Dot Matrix and Daisy-Wheel Printers

    So you took your printer apart....

    "I stupidly took apart my Panasonic KX-P1123 to attempt a head swap (the cable was too short!), now that it's back together it just beeps when I try to print. The only things I touched were the rod that the head assembly slides on and the toothed belt also had to come off (I don't think it's a timing belt.. there's no clear markings suggesting that). When I try to print, the head moves to the center, there's no pin action and it starts beeping at two second intervals (and won't stop). It's not the paper sensors because they seem to work properly...any ideas?"

    (From: Filip M. Gieszczykiewicz (filipg@repairfaq.org).)

    Greetings. A few:

    1. Make sure you didn't trap and crimp any wires .. there SHOULD be a 'Column 0' sensor - either a photo-interrupter or a switch. The print head will activate it during the self-init.

    BTW, move the carriage all the way to the right, close the cover and turn it on - does the print head move or does it just sit there and beep?

    1. Ensure that you have the ribbon cable correctly hooked up between the printer & head .. some [smarter] printers can tell... I am not sure about that one, but some printer have an optical (IR) sensor that detects ribbon presence (or am I spoiled with fixing $$$ printers? :-)

    2. This should be obvious - but does the print head move FREELY all the way from the left to right and back? Don't forget to oil (not too much!) the rails!

    3. Did you reconnect all the cables? Is the front-panel (display+buttons) attached?

    More depends on the answers and results of the above. BTW, most newer dot-patrix printers just need 2 screws to be removed to release the head. I know the Epson LQ-1050 works like that (and many of that Stars as well). Anyones needs parts from the former? I have one with a dead head (and it's not economical to repair).

    Print head repair

    "I have a few Epson dot matrix print heads with stuck or sunken pins. Does anyone have experience with disassembling these things for cleaning/repairs? It looks like you just have to pop a few clips to get them apart."

    (From: Chris Serrano (brace@loop.com).)

    I resurrected one by hanging it pins downs in an ultrasonic cleaner. A lot of old dried up ink floated right out and the stuck pin became obedient again.

    (From: Filip M. Gieszczykiewicz (filipg@repairfaq.org).)

    Greetings. If one does not have the use of an ultrasonic cleaner, I have found a different way to get these suckers working again.

    Go to your local plumbing store and look in the chemicals department for 'CPVC-PVC-ABS CLEANER' (used to clean plastic pipes). This stuff is a combination of groovy chemicals Methyl Ethyl Ketone and Acetone. It will 'melt' most plastics so be sure the print-head's any plastic parts are safely taken off.

    Pour some of this stuff into a GLASS container and put the print head, business-end first, in it and leave it there for a few minutes. When the stuff turns dark-purple (all the ink and goo from the print head) you are done. Let it dry (few minutes) and then oil it with LIGHT OIL. Note: Do NOT use WD40 - we're interested with something that sticks around for a few months... WD40 just leaves a 'protective layer' with almost zilch lubricating properties (it's a Water Displacer (WD), after all).

    I have done this for a few DataSouth DS-180, Infoscribe 1000s, and Xerox [monster] printers that see a box of 132 column paper a month (each) for a number of years with excellent results. Note: YMMV... these printers have rugged print heads (7/9 pin)... I don't know how a 24-pin Made-in-China feather will respond.

    Ribbon does not advance after replacing flex-cable

    Have you actually confirmed that your 'new' ribbon cables are making proper contact - with an ohmmeter? Assuming that the thing worked better before the cables were cut, then there are only two possibilities: your replacements aren't quite right or something was damaged by the 'event' or through later actions.

    Print head stepper

    Confirm that you simply don't have bad solder connections around the plug to the motor. This is common in printers and will result in erratic or incorrect motor movement.

    (From: Ralph Wade Phillips (ralphp@gcstation.net).)

    What's common in some older Okidata 32x's and 39x's is that the lithium battery *above* the stepper driver will spring a leak, and drop the lithium compound onto the legs of the stepper. I do not know for sure if it's corrosive, conductive, or just plain nasty, but it kills the stepper deader'n'snot.

    I'd LOVE to find a replacement - I've got a service customer that has about 2,500(!!!) 320's and 321's in the field, and I am not looking forward to having to exchange all those boards over the next several years.

    Motor driver blows fuses

    The following was in response to a dot matrix printer blowing the power fuse whenever the paper advance motor was driven. A 74LS273 was getting hot as well:

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    I'm going to guess (based on what I've seen in other printers) that there's a set of power transistors (either H-bridge drivers or 1 per coil, depending on the motor) that drive the stepper. These transistors are driven from the printer's microcontroller via an output port - in this case the '273.

    Now, if a TTL chips is getting very hot, then either something is drawing too much current from it, or something is overvoltaging one of the pins. A particularly unpleasant failure mode is when a PNP power transistor, with the emitter tied to the V++ rail (the 20V + rail that supplies the motors) decides to short and apply said voltage to the output of whatever device is driving it. If you're unlucky, the next stage is that the output port device breaks down as well, and the CPU data bus gets 20V or more on it. The result is blown chips all over the printer. Please don't ask how I found that out ;-)

    My guess is that there's at least one shorted transistor in the stepper motor drive circuit. If the system uses an H-bridge driver (an equal number of NPN and PNP transistors) then if one transistor shorts, its companion is connected across the power rails. When it turns on, the supply is effectively shorted.

    I think you'll have to trace out the driver circuit for the stepper motor. Figure out what drives what. Test the transistors, and then replace the defective ones _and_ that '273, which is probably now blown.

    Ribbon on electronic typewriter does not advance

    "My wife has a "Smith Corona" Model SD800 electronic typewriter that will not advance the ribbon. Everything else seems to work fine. We have been unable to find a local repair for this unit. I think I can fix it with some advice from someone familiar with these machines."

    Can you determine if it is a mechanical or electronic problem? For example, with the ribbon removed, does the gear or post that drives it appear to try to turn or not at all?

    Modern electronic typewriters are a combination of keyboard, microprocessor, and printer. Therefore, the same sort of troubleshooting approachs can be used as for computer printers.

    Common electronic problems include bad connections to the motor that advances the ribbon (cold solder joints, cracks in traces on flex cable to carriage), bad motor driver chip, or bad motor.

    Mechanical problems include stripped or broken gears, misalignment preventing advance mechanism from engaging, and defective ribbon cartridge.

    (From: Roger D. Waddell (rwaddell@peachnet.campus.mci.net).)

    This problem is usually caused by a broken 'E' clip on the bottom of the print hammer solenoid. The clip holds on a lever that works in conjunction with the ribbon/correction feed solenoid near the right front of the print carrier.

    When the clip breaks, the lever falls out of position and never trips the lever that assists in feeding the ribbon.

    I have seen this problem many times!!

    Apple Imagewriter II squeal

    "My Imagewriter II, after many years of faithful service (~8), is starting to squeal. It squeals when the carriage moves. It still prints perfectly fine, but....a new noise can only mean trouble. Does anyone have any experience with this problem and his solution? I imagine it would take only a drop or two of lubricant. But where?"

    (From: Chris Jardine (cjardine@wctc.net).)

    I would suggest that you might have a problem with the ribbon mask. A few years ago I was the service manager at an Apple dealership. I can't tell you how many ribbon masks I replaced for many different problems, including wierd noises. It could also be a problem with the carriage drive motor. I can't remember which side of the printer it is on, but, it is below the gear/pulley that drives the toothed belt. You might try some very fine (maybe silicone) oil there and you might want to clean and then re-oil the carriage guide bar (the shiny round bar) and the bushings on the carriage that ride on the bar. The only other possibility would be a problem in the gears below the ribbon that are responsible for driving the ribbon.

    Compaq Pagemarq 15 printer service mode

    (From: Darren Mckillop (Darren.Mckillop@gecm.com).)

    Try powering on while holding escape, this will put you into service mode. Press the up arrow to start the engine test, if this works you may have a problem with the xerox controller board.

    Try disconnecting all the n/w cables and reseating the cables on the system board. Remove this by the two thumbscrews at the back and slide out as far as you can then pull the cable off.

    I have a Compaq Pagemarq 15/20 service manual that I am selling, but I am in the UK, where are you?

    Epson FX-286e printer problems

    "I just received the above printer in a non-working condition. It exhibits the following symptoms:

    When power is applied, the head appears to try and move, but will not unless you manually get it started. Then it goes to its home position. You then hear three beeps, and nothing else can be done to elicit any response from the printer. The power LED comes on, but the paper-out will not, regardless if there is paper installed or not. The paper detect switch is working properly (checked with ohmmeter by inserting/removing paper while across switch). Also, I hooked up a resistor and +5v to the paper-out LED, and it lit up ok. I have also mapped out the stepper motor leads, and resistance checks show that it appears to be ok.

    MY question is if perhaps I lost one of the outputs for one of the stepper phases. The controller seems to be one large power-ic from what I've traced out."

    Could be. Do you have a scope? You could check the phases.

    "I know if you keep voltage across one phase, you can lock a stepper. If you lose power to one phase, will the other phases keep it going provided you manually start it like I'm doing?"

    Also check for bad connections to the stepper from the logic board - I have seen these on printers.

    It doesn't explain your other problems, however. Once initialized, even though the print head doesn't move properly, I would expect the printer to work in other respects.

    (From: Joe Wagg (jwagg@fs.cei.net).)

    The 3 beeps tell you there's a carriage error, probably from an incorrect number of steps needed to reach the home position. Since you've already checked the motor, the next step is to check the motor drivers. Using a meter with a diode check function, put the red lead on ground and the black lead on each phase coming from the board (disconnect the motor first). The readings should be within 20 percent of each other, not open or shorted. Also make sure the motor, pulleys, and carriage are all relatively clean and move freely. The other symptoms are caused by the carriage error, which halts the cpu to prevent damage. Clear up the carriage error and the other problems should go away. You should also make sure that all socketed chips are properly seated and don't have dirty contacts.

    Paper debris clogging Epson LQ-570

    "I have an Epson LQ-570 series dot-matrix printer that has developed an intermittent paper feed problem over the past year or so. It uses a push tractor for sprocket-feed paper, and paper tends to bunch up under the platen. There doesn't seem to be an obvious way to remove the platen to see what the paper's catching on, indeed the FAQ on Epson's website says it can't be removed, and to bring it in to the dealer for repair."

    (From: Asimov (Asimov@juxta.mn.pubnix.net).)

    Remove everything that is normally accessible. Then flip the printer on its back and play a vigorous drum roll all over it. This should dislodge a huge amount of "holes". Didn't you always wonder where those perforations went? Well, some of them make it into clogging up under the platten.

    Flip the printer on its side and with a thin brush dust the remaining grime away. If the jam didn't clear up you might try manually inserting a stiffer paper (postcard, greeting card, etc) a few times before dismantling the platen assembly any further.

    IBM X-24 Proprinter print head jumps around

    "Got a problem with a real nice 24 pin dot matrix printer I bought used. Was working fine for awhile then all of a sudden it will be printing fine an the printhead intermittently will jump to the center of the carriage and start printing from there. Also, when you turn it on, many times the printhead jams over to the right side of the carriage and the gears grind and you have to cycle it on and off to get it to start up right. Then you now almost for sure it will have problems printing. Help, any ideas? Do I just change a control chip? How do you scope out something like that? Can I get a manual somewhere? I want to keep the printer."

    Also check for bad connections. If the printhead motor is a servo (DC instead of stepper), you have an intermittent feedback problem, again could be bad connections or bad parts.

    (From: Ralph Wade Phillips (ralphp@gcstation.net).)

    First off, have you changed the RIBBON? Second, clean the print head carriage rails. They need a VERY LIGHT coat of VERY LIGHT oil, then wiped clean.

    Usually, when I see this, either the printer is just plain wore out, or the ribbon is snagging. Since the ProPrinter family drive the ribbon off of the carriage drive, if it ever snags, you'll get these symptoms.

    NEC P5200 Printer problem

    "I have a NEC printer that has an intermittent CE (ribbon cartridge empty) problem, only the cartridge is new and good. Anyone knows what senses this condition and what part could be affecting this? NEC wants $20.00 just to talk to me. Thanks for any help."

    (From: Paul Weber (webpa@aol.com).)

    Look at the old ribbon. Does it have a short piece of transparent tape at the end of the ribbon? If so, the printer probably has an optical end-of-ribbon sensor; a LED/phototransistor pair that looks through the ribbon. Does it have a short patch of aluminum foil tape (probably on the back side of the ribbon) ? If so, there is probably a pair of contact fingers that rub the back of the ribbon as it feeds. Look for bent contacts or debris in the ribbon holder mechanism.

    Look at the ribbon holder mechanism in the printer. Is there switch or contact pair that could sense the motion of the ribbon cartridge's feed reel? If so, check for free movement and cleanliness. Does the ribbon holder move with the printhead on this machine? If so, check that the ribbon cable connecting the carriage with the remainder isn't damaged and is connected properly at both ends.

    OKI Microline 391 Elite Problem/Error

    "I am having a problem with a OKI Microline 391 Elite. I opened it up and cleaned out the dust and paper from inside. On putting it back together and powering up, The SEL light, the COURIER font light, LW and 10 cp light are all flashing and the stepper motor for the platen is jigging back and fore about once every 3 secs."

    (From: Glenn Allen (pclogic@xtra.co.nz).)

    These printers generally need just a clean out and put back together.

    I would try to reseat the main logic board first, also try cleaning the edge connectors. There is a plastic joining bracket between the print head cable and the main logic board.

    If you are getting bad carriage movement then check that the carriage can move freely back and forth, also check the black teethed guide lying on the bottom for clogged teeth. The print head ribbon can be removed for better testing. if the carriage doesn't move freely then you may need to adjust it's position by loosening the two screws on either side of the print head carriage and then adjusting back and forth until good movement is achieved.

    Star SD15 printer self-test problem

    "This printer has a problem I am lost with. When I power it up and attempt to have it perform the self-test printout (FF on power up), the print head moves back and forth, the paper feeds, but the pins don't actually fire. However, if I connect the printer to a computer, the printing is just fine."

    You are complaining? :-) Usually, it is the other way around!

    (From: Ralph Wade Phillips (ralphp@gcstation.net).)

    Eh? On the SD-15, the FF SelfTest is for checking HEAD MOVEMENT only. It sounds like it passes just fine!

    Try holding down LINEFEED button instead. :-)



  • Back to Printer/Copier/Fax Repair FAQ Table of Contents.

    Ink-Jet Printers

    HP DeskJet problems

    This of course also applies to other HP printers as well!

    Hewlett Packard has on-line information and documentation at:

    Types of HP ink-jet technology printers

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    The PaintJet printers are 180 DPI and the DeskJet printers are 300 DPI. The resolution of the PaintJet is about that of a poor 24 pin printer. The PaintJet and ThinkJet printers are also PCL, so you can use a HP laser printer driver set to 150 DPI.

    There seem to be currently four levels of HP ink-jet printers:

    1. ThinkJet/QuietJet: The original. Small see-through bladder cartridges. These are small, compact, quiet, form-feed printers. Text quality was about that of a 9 pin (I still love the little ThinkJet printer; damn near indestructible, small, and built-in Epson emulation). (BTW, look in the 1989 HP Optoelectronics handbook for the datasheet of the miniature ThinkJet cartridge). Original cartridges needed special paper for best printing. Replacement cartridges that print on plain paper are now available.

    2. PaintJet: The first color printers. Cartridges are bigger, 'squarish' and usually are mounted horizontally. Resolution is the same as their 'little brothers', the Thinkjets (180 DPI). There are black, combined color and separate color cartridges (and sizes) available for the different printers. Printers were generally form-feed.

    3. DeskJet/DeskWriter: 300 DPI. BIG improvement. Cartridges mount vertically. Black and combined color cartridges are available. Printers are sheet feed and plain paper printing.

    4. DeskJet 800 series: 600x300 DPI B&W, 300x300 DPI color. Cartridges are tall and narrow and mount vertically. Damn near laser quality w/special paper.

    Dissertation on HP DeskJet repair

    These comments are in response to: "Repair Brief #49 - Part 1: HP DeskJet Professional Printer - Dead" and its followups. My text is indented. See those articles for details. The quick summary is that I picked up this printer at a garage sale and first had to dry it out and repair some cold solder joints before it would print at all.

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    I've dealt with a few of these buggers before! ;^)

    Is yours a DeskJet, DeskJet Plus, or any of the DeskJet 500 or 600 series?

    If not, then ...well....then I may as well tell you this anyways because you will probably run into these some day....(some of the below can apply to other ink-jet printers).

    Try holding down 'FF' during power-up, you may get a different test page. One of the pages should have a jet-test pattern (A slanted diagonal line separated by 11 vertical marker lines and little jet ID numbers).

    The first page of the standard self test results in that pattern.

    I first tried the cartridge that looks exactly the same as the one that came with the printer (though the part number is different). Then, I tried another somewhat larger one that apparently has identical connections.

    The different part numbers are the 'standard capacity' and the 'high capacity' cartridges. They're interchangeable.

    I assume you have cleaned the contacts (with a Q-tip, on both cartridge and socket). Use a magnifying glass and check *each* of the gold 'bump' contacts. Repeated cartridge swapping, or improper insertion, can cause a crack to form around the base of the 'bump' and the pad (or the pad and the trace). The 'bumps' can also be 'flattened' by cartridges that were forced in at too much of an angle. There should also be some 'give' or 'sponginess' to the contact area to assure even contact with the cartridge.

    Check for broken/bad traces in the flex-cable that goes from the driver board to the cartridge. Ohm out the cable between the supply commons and the individual driver lines (at the PCB) with the cartridge in place. I think the jet resistance was about 50 ohms (It's been a while). There were four separate jet sections (commons). All four commons were tied to the +20V supply through four separate (12 ohm?) series current limiting resistors. The driver outputs seemed to be grounded emitter, open collector (w/clamp diode?). The jets themselves are driven individually and are not multiplexed.

    To test, I printed an all-black page (with an empty, but installed cartridge) and watched for activity on each of the lines at the PCB end. Good pulses are 'bi-levelish'. Normally negative going 20V, with pulses down around 15V, and going all the way near ground for that particular jet. The commons 'bounce' because of the shared series current limiting resistor, causing the numerous smaller pulses around 15V (caused by the firing of other jets sharing that common). A bad connection will show up as a weak or distorted pulse. An open or broken line will show up as 0V. I theorize that a bad driver would show just the smaller 'line bounce' 15V pulses and a shorted driver would show 'GND' (and also would blow out that jet!).

    The current involved to drive the 'jets' is a pulse of short duration and pretty high current. Any poor connections will cause excessive I/R drop and the jet may not fire hard enough. A sign of this is drops (dribbles) of ink that form on the head during printing.

    While you are in there, check and clean the rectangular rubber seat that the cartridge rests on in the 'parked' position. Dry ink can cake up on it, causing a faulty seal and resulting in dried-up cartridges ($$$!). The rubber seat pulls off and is easily cleaned with a wet paper towel (wear gloves, or you will suffer the dreaded 'black finger syndrome'). Also clean the 'nose wiper' that sticks up about a centimeter to the left of the cartridge seat. This always cakes up and can cause printing problems.

    To manually prime an uncooperative cartridge, you do not have to suck on the business end. You can gently blow into the top vent (located on the top of the cartridge, inside the green arrow) to prime it. But be careful!; If the jets are severely plugged, ink may blow out the check-valve on the bottom (under the plastic 'flap' with the 'maze-like' area). Very messy! Have a towel ready!

    The old DeskJets were (and still are) notorious for paper feed problems as they age. This is caused by the three big paper pick-up rollers drying out and becoming hard and smooth. Roughen them up with some rough sandpaper. The HP FTP site has a article about this in the DeskJet DOC directory. A free kit is available from HP (to qualifying S/N#'s) that 'dresses' the rollers (basically forces the rollers to turn and sandpapers them).

    OH! Biggie! Another big 'failure mode' of the early printers is that the paper sensor lever will jump out of position and jam if the printer has suffered some rough handling (especially if it was turned upside-down or on it's side). The paper sensor lever (pivot) is located on top above the middle roller. The other end breaks the beam of a photosensor. The 'interrupter' end will move over just enough to wedge itself above the photosensor. This is cured by simply raising the lid and wiggling it until it drops back into position (I have 'fixed' many an alleged 'broken' printer this way). The 'interrupter' end seems to have been made larger on the later printers to prevent this.

    From time-to-time, the cartridge's nose should be wiped clean with a soft, moderately damp cloth (~ every 100 pages). Keep the 'business' end pointed down when handling/cleaning the cartridge (Yes, this means hold it above you and clean it from the bottom!). This keeps the galleys and jets primed.

    I concur. If just *one* jet is not firing, then it is on the driver/flex- cable/connector/cartridge side. All the nozzle decoding is done on the driver board, so the 20 pin interconnect cable is okay. The DC (well..really 20VAC) power connector does take some abuse in normal service, this could have aggravated the cold joint.

    Don't forget to check the buttons for water damage/contamination.

    I also have a color PaintJet 300 with a possible "dead" driver line, but I focused my attention to the ailing DJ500, so I did not have a chance to "buzz-out" the PaintJet cartridge. From looking at it, it looks like the PaintJets are multiplexed in some way (there are more jets/contacts than wires in the flex-cable). I never got around to fixing/looking into it (it's still sitting there).

    BTW 1; The DeskJet, DeskJet Plus and DeskJet 500 (non 'C' models) are basically the same (except for some internal fonts). The DeskJets speak PCL, so if a driver for a DeskJet is not available, you can use a basic HP LaserJet driver (but the margins may be cut off, as the DeskJets print area is not as big).

    These things are so damn simple that not much can happen to them. I have yet to run across one with a severe electrical problem. They are always minor mechanical failures (or missing power bricks...$35 from HP).

    All the DeskJet/DeskWriter printers, up to and including the 6X0 series, use the same B&W cartridge as the original DeskJet. Those cartridges will still be available for some time. Your printers life is not over any time soon!

    The DeskJets are good, sturdy and reliable printers (as long as they are well maintained) You did clean the rubber cartridge seat and flap. Right?.

    BTW 2: For maximum cartridge life, make liberal use of the "draft" setting for "not-so-important" printouts (or, er, um, drafts!). It also prints faster because it "swipes" once per line instead of twice.

    BTW 3: Use the cheap 'Shark' brand inkjet paper for best results. Pretty near laser quality! Regular copy paper tends to bleed, but is fine for general use.

    Can you tell I have a 'few' of these printers around???? ;^)

    Is the cartridge full? As you get down to the last 20% or so of the cartridges capacity, it tends to start doing this. I guess there is not enough pressure "from above" to force the ink down. If you can start seeing through the cartridge, you are probably near this point.

    In troubleshooting the printer, you tend to "burn up" cartridges a *lot* faster than in normal use.

    This can be a symptom of the print head not seating firmly when in the "parked" position. Use a dental mirror and make sure the seat presses firmly against the head. One cause of this can be turning off the printer before it has a chance to run through all of it's "housekeeping" cycles at power-up, reset (re-boot), or after printing. During certain parts of the cycle, the head is moved slightly, or the cover is moved. Turning off the printer too soon may leave the head exposed. Always let it finish, then turn it off (warn others about this).

    If you haven't already, just pull the thing apart and give it a good overhaul (get your favorite pair of Torx bits ready!). Clean all the rubber tires, seals and "nose wipers". Wipe off the slider bar to remove any old lubrication. If there was a serious ink leak and the printer was involved in some "circus acrobatics", some of the ink can get on the slider bar and contaminate the factory lubrication, causing it to become "pasty". I wipe the slider bar clean with a cloth then apply a *light* coating of a light, teflon-type machine oil with a cloth (I use "Tri-Flow", a spray-on type usually found in bike shops).

    BTW 4: In the winter months, with it's low humidity, the rollers will shrink even more, causing even more paper feed problems. This is also compounded by the fact that the paper sometimes develops a static charge and tends to "stick" together. Sometimes it pulls two or three sheets in at once, or the paper sticks firmly together in the tray and the weak, dry rollers cannot pull the paper in. Just remove the stack of paper and "fan" it out to loosen it (especially if it has been sitting there unused for a couple of weeks).

    These printers are, like some other things we won't mention, 'Use `em or loose `em'! They work best with frequent use. They do not like sitting around for months unused. Three months seems to be the limit before a 'good' printer will start to dry up from no use.

    I never really investigated the timing of the pulses. I'm not sure how they vary the pulse width. I looked at the pulses when it was doing the first page of the self test, which is mostly text, and all the pulses seemed to be the same width.

    Happy printing!

    HP ThinkJet printer repair 1

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    The ThinkJet is VERY simple. The ThinkJet printers (and clones) do not employ any type of printhead covers or 'priming stations', so the cartridges are prone to drying out if not used for a while. A quick 'priming' is usually required, even after only a week or two of non-use.

    The cartridges also tend to leak if placed in odd positions or subjected to rapid temperature changes. Make sure the cartridge has not drooled on itself and caused ink to cake down on the contacts in the holder. Clean the gold contacts *gently* with a cotton swab moistened with rubbing alcohol.

    BTW: Like motor oil, fresh ink is great for cleaning up old, dried-up ink.

    The ink is contained in a rubber bladder inside the plastic shell. There is a hole in the 'butt-end' of the cartridge. *Gently* stick a bent paper clip in and push on the bladder to prime it. A drop of ink should form on the printhead. Use a piece of tissue to wipe the drop off and re-install the cartridge.

    Note that there are two types of HP ThinkJet printheads. One is the older, original type meant for printing on special 'ThinkJet' paper, and the newer 'Plain Paper' ones meant for, well, plain paper! ('PLAIN' will be printed on the side of the cartridge).

    The older cartridges printing will appear very light if printed on plain paper. Make sure you have the 'Plain' type. Note that even with a 'plain' paper cartridge, the printing is lighter than a Laserjet or DeskJet, especially in draft or single pass modes. Don't expect razor sharp printouts. This was the first Inkjet printer!

    As for the missing jets, eyeball the cartridge contacts and see if they appear straight and aligned correctly. The contact area could have slipped and may be out of alignment (although rare).

    The flex cable/connector assembly is held in place with a pair of plastic bars. The "bars" have two pins that snap into the 'carriage' (they also provide alignment).

    If the contacts appear to be out of alignment, carefully pull out the plastic bars to release the contact pad, realign the holes and press them back into position. Make sure the rubber 'bumps' behind the contacts are clean and undamaged.

    (This makes more sense when you actually see it :^))

    Be careful! Nothing needs to be forced.

    HP ThinkJet Printer repair 2

    "I have an HP ThinkJet 2225C printer. I just replaced the print cartridge. It still doesn't print dark enough, and even after I primed the cartridge a few times, it still also misses a dot at the top and the second one from the bottom.

    I'm wondering, could the voltage to the cartridge be too low?"

    (From: Kevin).

    I have seen on rare occaisions the cartridge bad out of the box! Try wiping down the cartridge head & contact points on the printer with a Q-tip & alcohol. Sometimes blowing in the vent holes will force ink out the head, wipe off excess and try it. You may have to repeat the procedure a few times. If this doesn't work get another cartridge. You may want to try swopping the bad cartridge into a working unit or taking a working cartridge and putting it in the suspect printer.

    (From: Frank Reid (reid@indiana.edu).)

    I agree with all Kevin said. I use blue window-cleaner (e.g. Windex) instead of alcohol; the ink is very soluble in that stuff, and it penetrates the tiny holes in the printhead. After cleaning, hold a rag over the printhead and sling it downward a few times (as if throwing, but don't let go), such that centrifugal force pushes some ink out. If that doesn't work, try blowing on the upper vent.

    On a few rare occasions I've encountered bad connections at the fixed end of the printhead cable, fixed by reseating the connectors. Also, if the cartridge has leaked, there may be ink on the gold pads in the moving end of the printhead connector, causing bad contact. Clean as above.

    Some of the later models, including the type which takes two cartridges (3-color and black), have screws at the end of the carriage rod which allow adjusting the clearance between printhead and paper. Those may need adjusting if the ink is smearing. If too light, it's probably a printhead problem.

    (From: Richard M. (Digitech@bogus.net).)

    It is a water based ink. There is no need for any solvent other than water. Warm water works well. Use it all the time on my 1200C and DJ750C... BTW, I never have to touch my Epson. Use lint free cloths to tamp dry. NEVER wipe.

    (From: R. Wagner (rwagner@ncn.net).)

    I found the cable from the computer to the print head had some open places close to the head. The want 35 dollars for a new one. I went to the auto parts store and got some a rear window defroster repare kit. I got it working but for how long I dont know.

    HP DeskJet paper feed problems

    (From: John T. Black (cz667@cleveland.Freenet.Edu).)

    The paper feed problem afflicts the HP DeskJet 550C and 560C, DeskJet 520 and DeskWriter 520 printers produced between June 1993 and March 1994. The affected units have serial numbers beginning with 'US3' through 'US43.'

    The problem seems to be that the rubber rollers become slick over time and then the paper doesn't always feed properly. Last year HP offered a free paper-feed cleaning kit to fix the problem. Try contacting HP at 800/656-2324 or 510/657-1473 (FAX) to find out if the free kits are still available.

    (From: Allen E. Amey (a_amey@ix.netcom.com).)

    Try contacting the manufacturer. I have heard that HP has a free kit for the 500 series printers. The kit dresses the rollers and is supposed to be a fix for the type of problem that you are experiencing. BTW, using alcohol can actually compound the problem by prematurely drying out the rollers.

    (From: FaxRepair (faxrepair@aol.com).)

    I believe the only replacement part would be the entire paper pickup assembly which may need to be replaced because the gear train is damaged from ink having dripped onto it. Once the gear train is out of timing there is no known cure. Clean the rollers with rubbing alcohol and a soft cloth. If it doesn't pick up the paper after cleaning the rollers, then remove the entire print assembly and look for signs of ink on the gears at a location directly below the ink cartridge's home position. On a few occasions I have had success by flushing the gear mechanism with warm water to wash away dried ink.

    (From: James E. Burke, Jr. (jeburke@ibm.net).)

    I fixed one for a friend a couple of months ago. Parts are not available (well, you can get them, but they're too expensive).

    In the one I fixed, it was a broken plastic part that caused the misfeeds. To get to the part, I had to disassemble the whole printer.

    If you decide to to this, check the two 'fingers' that are behind the print head when it's in the parked position. The hook on the tip of one of them was broken off. I found the broken part inside the printer and glued it back on with JB Weld (twice--first time backwards). The pair of 'fingers' are identical so you could probably swap parts from one of the other machines instead of attempting the repair of the "fingers".

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    I have the same problem.

    The rollers dry up and become glazed-over and smooth. You need to 'rough' them up.

    Try sandpapering the wheels with coarse sandpaper (100 to 200 grit).

    You'll need to trick the paper sensor. Take the cover off and lift-up on the black paper sensor lever. Then hold the piece of sandpaper firmly against the wheel and hit 'FF'. You'll need to do this repeatedly, as the wheels will only spin a sheets' worth each time.

    Do this until the wheels feel 'sticky' again.

    It also helps to keep the paper tray full at all times (but not overloaded).

    Unfortunately, they'll never be like new.

    (From: Frank Reid (reid@indiana.edu).)

    I've had very good results cleaning the rollers with naphtha or mineral spirits, no sanding. It removes the glaze from the clay content of the paper, and makes the rollers softer.

    (From: (Egiglious Giggles" (chsoccer@prodigy.net).)

    The thing I have come across, is the spring which is directly under the roller itself. The purpose is to allow tension on the roller for pulling the paper in one sheet at a time. If you look directly in the middle under the roller from the front there is a guide that is spring tensioned. You have to take the roller assembly apart to get to it. But, if cleaning the rollers doesn't do the job, this is probably the culprit.

    (From: Tony Dunlap (tdunlap@odot.dot.ohio.gov).)

    The "Glaze" that gets on the rollers is often due to the rag content of many cheaper papers (especially "Recycled"). To clean the rollers:

    1. Remove the paper and paper tray.

    2. Send a short test page to the printer with the paper out. This will cause the form-feed light to blink.

    3. Wet the rollers one at a time with a cloth (not a paper towel) dipped in alcohol, while pressing the paper feed button.

    4. While it is wet, rub it with something rough and non-porous (I modified a toothed chip extractor that came with a pentium upgrade kit), again while pressing the paper feed.

    5. Wet it again with a fresh part of the cloth dipped in alcohol.

    6. Dry it with a fresh part of the cloth.

    7. Put it back together and let it print the test page.

    Cartridges drying out on early HP DeskJets

    Note that unless the cartridge is almost empty anyhow, it can usually be revived by patting off the caked ink with a damp lint-free cloth and then gently blowing in the vent hole on top until a drop of ink appears at the print head. Sometimes this may have to be done more than once. NEVER poke anything into that vent hole or you will have a mess!

    (From: Paul Weber (webpa@aol.com).)

    HP had a free upgrade kit for the 560 to solve this, maybe for the 500 as well. It was a replacement for the silicone rubber park-position nozzle seal. Also remember that the 500 came with a cartridge storage box with an elaborate rubber seal in the bottom; they encouraged you to remove the cartridge from the printer and put in the box whenever it wasn't in active use to prevent dry-outs. Finally, HP cartridges have expiration dates - and they mean what they say: If they're out dated, they work poorly or not at all.

    HP DJ340 shuts off during printing

    (This may also apply to other battery powered printers.

    "Whenever I send a heavily formatted print job to a DJ340 printer, it prints 1/3 to 1/2 a page and then power shuts off! This so far has happened in TTAX97 and Netscape 4.03. OS is Win95 and I'm using the latest driver for this printer. The printer otherwise prints test pages and simple jobs OK."

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    I know this sounds silly, but how old are the batteries?

    My guess is that the battery is probably getting weak. Heavy graphic content and "fancy" fonts users (of which TTax and Netscape qualify) will "swipe" the head more per line than the "text and lines" of the test pages. Moving that print head uses a lot of power!

    Does the unit work on the adapter - without the battery? If not, then it relies mainly on the battery for power, and the adapter just charges the battery in between jobs. A weak battery could be drained after a short time.

    If it works without the battery, then the battery could be going bad, causing the charger to dump too much current into the battery and "rob" some of the power from the printer.

    There is a "Troubleshooting" note in the printers "FAQ" on HP's site.

    It basically says to check the batteries and make sure you are using the correct power supply.

    Try replacing the battery. If you bought it at a local store, take it back and see if they have another battery to check it with.

    HP DeskJet 520 - Crunch!

    "I just picked up an HP DeskJet 520 printer that doesn't work. On startup, the print head moves right an inch, then all the way left, where it slams into the left side of the carriage and grinds away for about a tenth of a second before stopping."

    (From: Tech Guy (patrickmcardle@sprintmail.com).)

    You may wish to check the undercarriage (no pun intended).

    The printhead location sensor microswitch may be on the fritz The printer uses this switch to determine the starting point of the printhead after which it uses assumed location by how far the data has sent the head every time the unit gets a reset code, it checks this switch and if the signal is not detected, it may slam the head to either rail end or not move at all. If this is the case you can make sure that the platen is not clogged with label or paper debris. Gently move the head by hand to the right. If you shine a bright light into the area where the printhead usually calls "home" you may be able to see this switch (it may however be located under a cover triggered by the belt) if the switch is defective, replace it. If in fact it is jammed by debris, simply clear it and you may have solved the problem. Beyond this, you may have a logic problem (bad chip or other component) I make a good practice of doing a thorough cleaning of all machines that have left my shop to reduce the possibility of other problems during my warranty period. (it also makes the customer think that they have gotten something for their money)

    I have replace a switch or a fuse on many machines, charged my base fee and heard the response upon their pick-up by customers that, "I can tell right away that you have found and fixed the problem" without even so much as a demo.

    (From: michae98@ix.netcom.com).

    There is a clear plastic strip strung between the both ends of the printhead pathway. This strip of plastic has microscopic vertical bars which the printhead can read and sense what position its in the pathway. The strip may be contaminated with excess ink which may confused the printhead. Take a soft cloth or Q-tip dampened with water and wipe of the strip (the ink is water soluble) and the printer should work.

    (From: Raymond Carlsen (rrcc@u.washington.edu).)

    Closely examine the toothed belt that drives the printhead. Look for a few missing teeth at one end. I managed to make one work again by shifting the belt over a bit (past the bad teeth). If that's it, the belt should of course be replaced.

    HP DeskJet 560C Detailed problem description and possible solutions

    "I have a HP DeskJet 560C, Model C2168A that is behaving badly. When I power it on initially, it appears to run through a diagnostic self-test (as evidenced by the sequence of LEDs on the control panel). It gets to the point where it moves the print head and that is where things go bad. I think it is attempting to report some sort of error code because it then flashes some of the LEDs in a repeating pattern (more on that later).

    First let me describe mechanically what it is doing. When it gets to the point in the power-up routine where it moves the print head, it should do the following:

    1. Move print head to the extreme right.

    2. Prime the print head (???), a stepper motor on the right raises a mechanism to contact the print head.

    3. Position the print head in a ready position.

    OK, here is what it is doing (please forgive my feeble attempts to describe in words what is happening):

    1. I hear three distinct sounds (whirring of various stepper motors I think) before the print head moves.

    2. The first two sounds seem normal from what I can remember when the printer used to work.

    3. The third sound is the loudest and doesn't sound at all normal. It sounds as if the stepper motor that does the priming is oscillating back and forth between two "steps" (the sound is like a stripping gear).

    4. The print head moves approx. 1" to the right.

    5. The print head immediately moves approx. 1.5" to the left (note, this sequence of print head movements happens bang-bang (no delays between movements).

    The end result is that the print head winds up about 0.5" to left of the position it was in when the unit was powered on. If I continue the power on sequences enough times it will end up at the extreme left and will be accompanied by a much uglier, more sinister sound of the print head slapping against the leftmost guard (as if the printer is attempting to throw the print head through the case).

    Now let me describe the sequence that happens with the LEDs. The control panel has 9 LEDs arranged in three columns of three LEDs each. The leftmost column of LEDs lies between the "CLEAN" button at the top and the "Font" button at the bottom. The middle column of LEDs lies between the "Alignment Test" button and the "Status" button. Finally, the rightmost column of LEDs lies between the "Install Print Cartridge" button and the "Quality" button. Here is some ASCII art:

    
                                  CONTROL PANEL
     ===========================================================================
     ||                                                                       ||
     ||                                  Alignment         Install Print      ||
     ||  RESET          CLEAN            Test              Cartridge          ||
     ||                                                                       ||
     ||                 ,--,              ,--,              ,--,              ||
     ||                ( #1 )            ( #4 )            ( #7 ) o o o       ||
     ||                 '--'              '--'              '--'              ||
     ||                                                                       ||
     ||                 ,--,              ,--,              ,--,              ||
     ||                ( #2 )            ( #5 )Busy        ( #8 ) o           ||
     ||                 '--'              '--'              '--'              ||
     ||                                                                       ||
     ||                 ,--,              ,--,              ,--,              ||
     ||                ( #3 )Condensed   ( #6 )Ready       ( #9 )Econo Mode   ||
     ||                 '--'              '--'              '--'              ||
     ||                                                                       ||
     ||  Load/Eject      Font             Status            Quality           ||
     ||  Paper                                                                ||
     ||                                                                       ||
     ===========================================================================
    
    
    I have numbered the LEDs (using my own numbering scheme) so that I can reference them below.

    Here is the sequence that the LEDs progress through each time the unit>is powered on. The sequence is always the same.

          LEDs On       Duration                   Description
        -----------    ----------     --------------------------------------- 
      1. 123456789      2.5 secs       Happens immediately when I switch the
                                       power on.  Then LEDs 234789 turn off.
    
      2. 1   56         0.5 secs       This is a flash (longer than a blink).
                                       Then LED 5 turns off.
    
      3. 1    6         2   secs       Then LED 7 flashes on.
    
      4. 1    67        0.5 secs       This is a flash.  Then LED 7 turns off,
                                       LED 5 blinks on.
    
    **5. 1   56         ----           Here LED 5 just blinks on then off.
    
      6.  234  789                     This starts the alternating sequence
                                       where I believe the printer is trying
                                       to report an error code.
    
      7. 1    6                        This is the rest of the alternating
                                       sequence.  The printer then repeats
                                       these two patterns forever (LEDs 234789,
                                       followed by 16).
    

    ** Step 5 is the point where the printer starts moving the print head."

    (From: Jason D. Pero (JDP6640@ritvax.isc.rit.edu).)

    The grinding sound from priming area is the jammed lever black stick that is pushed towards a bit towards right. If it good, it should be in upright position. If stuck too very right, unstick it by pushing it back to upright position towards left. This stick can be seen between the carriage rod and the printhead's purging rubber nipples and wipers. Also clean (gently!) the clear plastic strip with that fine black lines on it. First the clear strip must be removed first before doing this operation: The sensor is behind the printhead riding the clear strip, remove it by unengaging two triangular fingers inwards from outside and pull the sensor unit outwards towards back. Dust off inside that sensor gap and snap it back in.

    Finally clean and oil both carriage rod and the angled underside area where the bearing block contacts upward onto it. Oil that carriage motor carefully and all stepper motors.

    That should solve everything. This have happened to my 520, and my friends' 540 and 560C. Pretty common problem! Usual action when misbehaving is slamming either stops or do a "rushed start/stop" and some odd scary noises. All complains with pretty, interesting alterating flashes from the LED's on the control panel.

    Pure or almost pure alcohol stuff is best as it does not melt anything or rub marks off and some 2 in 1 heavy duty oil "blue band" can. Top and bottom white shells comes apart easily after unengaging four snaps, doing one at a time and pulling gently and with a small flat screwdriver. Top off, the engine is free. disconnect with care to both ribbon cables one for carriage motor, and the flat white ribbon, or in some models that uses dual printheads, unplug another stepper motor. All connections you need to worry about is only from the mainboard side. Then the print engine lifts out without any fastening hardware.

    WELL DESIGNED 5xx series compared to many printers past and now! I have a 520 chugging away after this fix and real cheap for that printer from a owner who does not want it.

    Only problem is cost of cartridges. :( $50 of two versus $13 can of toner powder for an Okidata 400 that will last thousands of papers. Only problem is Oki. 400 LED laser thinks (processing graphics) very slowly. Is there a hack to swap the proper circuit boards from other similar Oki 400/800 series to make it work faster and more useful than a pokey 186 cpu equipped Oki 400???

    Your comments and suggestions on which brand of refill inks that is perfect for those cartridges. I know how to refill it right after experimenting on a bad cartridge and successfully refilling one good cartridge from a bad cartridge (dead jet out of 48 jets I think).

    (From: Glenn Allen (glenn@manawatu.gen.nz).)

    It is not a stripped gear is it?

    The old DJ500 used to have 2 levers on the right hand side at the back that went up and down. Sometimes these got stuck and noises could be heard. Normal paper feed problems here.

    A problem with a DJ850 was that paper got stuck and to get it out I had to remove the paper feed motor on the drive shaft, when put back it would bang the left hand side of the case. Needles to say it needed the cog setup back to right place it expects when powered on.

    Those printers have an index strip that the printhead follows doesn't it? Is this clean, i.e. Not ink all over the place.?

    Lastly if you are repairing and turning your printer up and down, check you do not lose the rubber cap where the printhead sits, and clears the guns, If you do your cartridges will become clogged in no time.

    Also clean the print head shaft, any gunk on it will cause the printhead head to stick thus giving error light or worst powers down the printer.

    Cartridge detection on HP DeskJets

    (From: Fred Keen (fkeen@repeatotype.com).)

    The HP printers test for the presence of a cartridge by checking the electrical voltages on the contacts between the cartridge and the cable. The slightest amount of dirt on the contacts can give a false reading making the printer think that no cartridge is present. If cleaning the contacts does not work you will have to buy a new cartridge.

    HP Deskwriter 660 printer problems

    "My HP Deskwriter is just over the warranty of one year and when I print text instead of white lines through the type which would indicate to clean cartridges or replace them, I get black thin lines almost smearing slightly the text."

    (From: Dennis Bathory-Kitsz (bathory@maltedmedia.com).)

    1. Take out the cartridges and clean their sides, which pick up hair.

    2. Clean the cartridge-cleaning mechanism itself on the right, especially the foam pad.

    3. Take out the cartridges and clean the bottom of their carriers.

    For this last, there may be some diagrams accessible via the HP Support Page.

    Little plastic parts in HP DeskJet printers and HP service policies

    (From: Wayne Van Beelen (wbvanb@nbnet.nb.ca).)

    The bad news is that the plastic these parts are made of seem to be a Teflon hybrid and even the best epoxy doesn't last real well.

    The even worse news is that DeskJets are disposable, just like Bic lighters.

    HP will NOT sell you any internal parts.

    They will not sell them to your dealer.

    They will not even sell then to a so called HP service center.

    All DeskJet service takes place in Corvallis, Oregon. A second possible location is Mississauga, Ontario but I think they just forward printers to Corvallis.

    Here's the deal as I've been told; you pack up your printer and courier it to Mississauga, ($40 Cdn.), pay $175 Cdn. for a refurbished version of your Deskjet, and then pay another $40 Cdn. to ship the refurb back to you. That's $255 Cdn for a used printer when there are any number of new printers that can be had for a comparable price (and would also have a warranty).

    That, to me, means DeskJets must be disposable because nobody in their right mind would pay that much for a three or four year old printer. It's bad enough when you consider 540's, which back then had a 3 year warranty, think about all the poor suckers buying newer HP's with only a 1 year warranty...

    That's got to be enough harping on my part, the short of it would be that if you've got it working and your cartridge parks okay, it might be best to leave it alone. You won't get any worthwhile out-of-warranty help from HP. Check on parts availability on any future new printers you might ever buy. You can't assume that they won't forget you the day your warranty expires.

    HP DeskJet 560C - stripping gear sounds and more

    "Does anyone know where the problem might lie with my HP printer? The problem is that when it is turned on, it goes through the reset sequence until it reaches the park zone, then it seems to miss a gear or something by the sound of stripping gears, then the lights flash alternately. My workaround to this is to turn it on, let it start across on it's reset sequence, turn it off, then right back on, and it will initiate just fine. Another anomoly is that when printing large color graphic files, occasionally, it will make it part way through the page and just stop with the same flashing error. After resetting it, it of course will print garbage unless I resend the data to the printer all over again. Any ideas? I've left a message on the HP site, but there has been no response."

    Call HP - After much hassle they finally admitted it was a defect and replaced it with a new 600 series. I had the same problem - but had to call Idaho to get results.

    HP600C DeskJet produces too much black ink

    In addition to cleaning the cartridge, replacing the cartridge, cleaning the ink "well" and rubber wiper used for wiping cartridge head, using "approved" paper, printing in econofast mode (less ink), and setting up "transparency" print mode (gives more time for drying), one thing is often overlooked:

    (From: Ralph Wade Phillips (ralphp@techie.com).)

    Did you also clean the cartridge HOLDER? See HP's web page for more details, but I've seen SEVERAL of the 600 family that have "dust" collected under the cartridge holder. Since the black hits at a different angle than the tricolor cartridge, it is more prone to hitting the dust buildup, causing excessive smearing.

    BTW, beware of flipping the entire printer over to unlatch the top - you may get a shower of the last n years excess ink from the holding tank!

    HP DJ power supplies/wall adapters

    It seems that this is one part that HP may not totally gouge you on!

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    Go to this page below, scroll down to the "power module options" section, and pick the correct adapter part number for the UK.

    Then do a net search for that part number, or, contact HP directly. Last time we ordered some, they were about $35US from HP.

    HP 600 series DeskJet printer smears even with new cartridge

    (From: Bill Rothanburg (william.rothanburg@worldnet.att.net).)

    I had a similar problem with a HP 693C. The problem was the spacing between the paper and the carriage. A suggestion: if you're not mechanically adept, don't tackle this, get someone who works on printers to lend a hand.

    I have not taken my 600C apart, and will not do so unless it fails, so the following information is based on the 693C, a similar printer.

    The top cover is held in place by some latches, and a couple of screws under the paper tray. Be careful while tipping the printer, there is a catch-basin for the ink, and if this spills you will have ink dripping inside the printer. Remove the upper cover. Be careful with the thin cable to the electronics board. At this point you should be able to check for any gobs of ink that have turned to paste. Clean the dried ink off of everything, especially the bottom of the carriage, and print a test page. If it still smears, it's time to try adjusting the carriage height.

    On the 693C the carriage slides on a rod that runs the width of the printer. The anchors consist of a screw through a slotted hole. On the one I fixed, the screws had obviously been loosened (they're torx screws, and it was obvious that something such as a jeweler's screwdriver had been used on them). Anyway, loosen the screw at one end, lift the rod slightly, and retighten. Print a test page, and repeat if it still smears. Of course, if it now smears only at the other end, it's time to switch ends.

    I'm sure at the factory they use a gauge to adjust this to within a micron but the empirical approach worked for me.

    HP DeskJet 692C - Random lockups

    (From: Jess Askey (jess@magenta.com).)

    I did a search when BOTH of my HP692C DeskJet printers started getting flaky. I didn't find much except for a post mentioning that cleaning the small plastic 'barcode' may solve most problems. While this is exactly what HP customer service suggested as well, it didn't solve my problems.

    What the printers were doing, were randomly locking up. They also started making a 'knock' sound while they were printing. But, the 'knock' sound was more prevalent than the actual 'locking up' problems. But they would still lock up more than twice a day.

    What I found was happening was that the stepper motor belt was skipping a tooth when the print head was changing directions. There is a black plastic tensioner arm on the left side of the printer that holds the belt tight and this was getting yanked in enough to let the stepper belt have some slack.

    What I did to fix this was to take the spring out from behind the black tensioner arm and stretch it out to put more tension onto the stepper motor belt.

    Both of these printers have had heavy use, they both are just over 1 year old right now too. I only moderately stretched the first spring and it still made the 'clicking' noise every so often. On the second one, I probably stretched it about 1/2" to 3/4" in it's fully relaxed position, but I think when putting it back into place it probably bent back a small amount. This worked well, the belt did not feel overly tight and I have not had ANY problems whatsoever. :-)

    HP 820Cxi DeskJet Problems

    (From: Vic Zane (vic@webworks2000.net).)

    I've been having a problem with the black cartridge in my HP 820Cxi printer getting all gummed up with ink on the bottom, making lousy print. Clean it off, and it comes right back. It also was missing a horizontal line or two - thin but noticeable. The "clean" instructions with HP troubleshooting didn't help at all. Interesting that they say there is another thing you can try, but don't do it except with NEW ink cartridges! At $30 or so each, I wasn't interested in trying that except as a last resort.

    The other day, after cleaning and refilling, I got an error message telling me that my black cartridge was no longer usable, and that continued use would possibly damage the printer. I purchased a new cartridge, and replaced. The old cartridge again had the buildup of ink on the bottom. So now I got the same "unusable" message, with recommendation that the cartridge be returned for replacement. And again, the bottom was loaded with ink. Obviously this was not just leakage from a faulty cartridge.

    Information found on the web indicated that HP has only one repair location, and will not sell repair parts to even their dealers. Probable repair costs, added to shipping two ways, lead me to believe that I would be money ahead by either repairing it myself, or junking the printer. It has been in service (I am a retiree using it at home) for just over three years.

    There should be information on this printer accessible on-line which is not included with their on-screen maintenance information:

    I also referred to this document at a Sci.Electronics.Repair FAQ site.

    I removed the cartridges, and stood them upright on a multi-thickness pad of paper towel that was moistened with distilled water (from dehumidifier), figuring that this might open any ink jets with dried ink in them. A flashlight helped to see the area at the far right of the printer, where the cartridges park. Those wipers were a real mess. The Q-tip swab technique proved quite unhandy, but with a larger wad of cotton on the tip of a long and narrow needle nose pliers, I was able to clean them. There is a well to the left of the wipers that appears to have a spongy material in it - well soaked with black ink. When I tried to clean it, it just depressed down into the well and stayed that way. The pads that rest against the cartridge bottoms when in the park position were inaccessible, as they retract when the carrier moves away.

    The paper toweling soaked up a little ink (I had some plastic under it). I wiped the cartridge bottoms, then replaced them in the printer. Alignment worked well - no skips or smudges. But I kept getting the error message telling me to cancel printing and align whenever I started printing, until the computer had been shut down and restarted.

    The printouts are now first class, and there are no more error messages. The "unusable" cartridges both work fine. Of course it has only been one day so far though!

    HP DeskJet 1200C power supply repair story

    (From: Marc Geyskens mgeysken@innet.be).)

    A while back, I got this broken down printer, most of the time the power supply wouldn't kick in after pressing the standby switch. After checking elementary things, I got stuck on the PCB that holds the standby switch, on it reside passive components, a few LM431 and a UN3854 all of the components where ok except for the LM and UN chips. Since I had no schematic and no sheet on the UN3854 I turned to the chip directory which led, via a few stops, to the Unitrode site and yes, a data sheet for the UN3851. Plugged my scope (power supply on isolation transformer) onto the ucc line for the UNxxxx, noticed that the voltage was almost 0 raising slowly to 12 V and then fast to 20V after that time the PS worked normal. So I traced the supply back to a FET 2SK537 on the power supply mainboard which is part of a protection, its gate pulled up by a zener ZD1 and a resistor of 680k from 400V and pulled down by a transistor in case of the transformer's output voltage gets to high. Well, it was the 680k resistor, infinitive resistance yet not a scratch on it.

    Thanks to the Chipdir site, and the Unitrode people.

    HP PaintJet problems

    "My HP PaintJet printer has a problem! When I turn the printer on, the print head moves as if it's cleaning the head but thats it! The "on" light stays on but the "SET TOF", "LF", and "FF" buttons don't work. I've tried a test page by holding down the "FF" button and turning on the printer but it won't print. It just goes through the head cleaning stage again and then stops. If I turn the printer off and manually move the print head to the other end of the carriage and then turn it back on again the print head will move back to it's home position."

    (Responses from: Paul Grohe (grohe@galaxy.nsc.com))

    I am assuming you have the original tractor-feed "PaintJet", and not the sheet-feed 300XL.

    It sounds like you have a problem with the "paper out" detector.

    Is the second lamp on, even when there is paper loaded?

    Here's a clue: If the other light is *on* after you do the self-test key sequence, then it thinks there is no paper loaded, so it does not print. The buttons are useless at this point, too. I have confirmed this with my PaintJet by removing the paper, and it does exactly what you describe. During normal "self test" printing, the paper out lamp is off.

    It is very common with DeskJets and PaintJets to have their "paper out" detectors jam after rough handling.

    Looking down into where the paper goes in, there is a little black lever sticking up (about 8cm to the right of the left end of the platen). This is the paper detect lever. The other end is a "flap" that goes between a photodetector.

    Make sure this lever moves freely.

    Open up the case (don't worry, it is very simple). Pull the big platen knob off. Then there are two rubber "wedges" stuck in two oval-ish latch holes on the bottom under the front "lip". Pull out the wedges and squeeze the latches. The cover then lifts right off (nothing is connected to it).

    With the cover removed and viewing the printer from the front, look at the bottom left corner of the circuit board. You can see the "flap" end of the paper detect lever and photosensor, right above the "made in USA" sticker. Make sure it moves freely and that it is situated between the two detector "blocks" (I have seen these levers "wedge" themselves against the outside edge of the detector).

    My guess is that you will either find paper jamming the lever, the lever itself mechanically jammed, or a piece of paper wedged in the sensor.

    While you have the top off, notice that there is a long, plastic strip with fine lines on it running along the front. This is used for sensing the head position. Move the head over and make sure that strip is clean and that no ink has spilled anywhere on it. Also clean out any paper dust or spilled ink.

    Don't be afraid to plug in the printer to test it with the cover off. The input voltage is only 20VAC, so you will not get shocked. Just be careful of the orientation of the power plug and watch out for the moving parts.

    BTW1: The PaintJet printer is very stupid. It will 'print even with the cartridges removed or the platen motor unplugged, so there are no other sensors that could be causing a problem.

    "The symptoms are that first the color cartridge got weak and stopped working and now the same has happened to the black cartridge. It's not out of ink or clogged and the contacts are all clean."

    The 3630 (aka: "PaintJet") was one of, if not *the* first, color ink jet printer. As such, it was plagued by the usual "first-of-it's-kind" problems. HP learned from their mistakes on this one!

    We have a few of them around here, and your experience is not unusual. They tend to "dry up" more often than the newer printers. I seriously doubt it is an electrical failure.

    Even though the cartridge appears "full", the ink gallies will clog if not used after a certain amount of time. After a week or two, you will need to clean and prime the cartridges.

    This printer does not have the automatic "priming" that the DeskJets have. Instead, you have to remove the cartridges and manually prime them with the "plunger" located under the "flap" on the top-left. Then "wipe" them with the rubber "nose-wiper" located on the underside of the cartridge access door.

    There is (supposed to be) a slide-out card located on the bottom of the printer with the "cleaning and priming" instructions (The little tab with the "i" on it).

    The PaintJet also lacks a rubber-sealed "cover" for the cartridge head when it is in the "park" position. This greatly adds to the "dry-out" problem.

    The head connector also creates some problems. The 3930 uses two rows of individual long, gold-plated "fingers" to make contact with the cartridge. These "contacts" can bend back, or become mis-aligned, due to improper cartridge insertion or wear.

    Take a look at these "fingers", and just make sure they are even and straight. Don't bend them too much, as they are brittle. Also make sure there is no leftover ink on the contacts. Don't press

    It should be easy to fix. However, you may go bankrupt replacing the cartridges.

    There are ink "refill" kits available, however, the problem is usually with the clogging of the internal passageways and jets. So new ink won't help much.

    My suggestions:

    Check the contact "fingers".

    Try "priming" and "cleaning" the cartridges.

    Try replacing the cartridges with known good ones (or new).

    If you will not be using the cartridges for a while, remove them and place them in a sealed container or baggie for storage (place them in the same position as they are in the printer).

    "What other printers are compatible with the PaintJet if I cannot get mine working and I need to use existing software"?

    The "PaintJet" is a 180 DPI, "PCL" language printer. Just like the "newer" DeskJets.

    If your unit has a parallel or serial interface, you can use any one of the older DeskJet printers (500/600 "C" series, DJ plus) - any that use the "PCL" language) or almost any laser printer (HPII compatible - B&W only). However, the newer printers are 300DPI printers, so the printouts will be 30-40% smaller.

    If it is a HPIB interface, look for a HPIB ThinkJet.

    Intermittent light/no print from Canon BJ330

    "I have a canon BJ330 that starts printing light and prints nothing. This only happens approx once every 2 months. The unit has ink and it still thinks it's printing but there is no ink on the paper. This has happened a couple of times and so far I haven't figured out what it is that I do to 'correct' the problem.

    I was thinking that there must be a way to clean the printhead that is not in the service manual. Which I do not have, anyway."

    On my DeskJet, I just blow gently into the vent hole on the ink cartridge. I then wipe off blob of ink that forms on on the head and it works like a charm - if you don't get ink all over everything. Perhaps, try the following first:

    (From: russrite@magmacom.com).

    Remove the sponge from the purge cap carefully, try washing in water carefully, and reinstall it:

    Canon BubbleJet information

    Parts Now! has a set of articles mostly on laser printer engines, but there is one for Canon BubbleJets. These can be found at:

    Canon BubbleJet printers not printing after cleaning

    (From: Handy (handy@redshift.com).)

    Take out the cartridge that you want cleaned. Find that hole that ink comes out of, squeeze the cartridge until ink comes out of that hole - actually drips. Put it back in the machine, clean it at least FOUR times. Usually on the fourth time for some reason, it works. Just clean the one that you think needs cleaning.

    Canon BJC 600 problems

    (From: Rob Connelly (connelly@ix.netcom.com).)

    I have found that sometimes the BJC 600 series gets confused and needs to be reinitialized. If you haven't already done so, unplug it from the wall, wait 60 seconds for the internal supply capacitors to completely discharge, then plug it back in and try again. When you remove it from the AC line it goes through a complete warm up cycle and resets itself.

    Also, the contacts that mate with the print head are notorious for oxidizing. You might want to carefully clean them (lightly) with a pencil eraser and some isopropyl.

    If these remedies don't work, the Canon 1-800 number will put you in touch with their tech department, and they are really quite good at determining what the problem is over the phone.

    (From: Al Savage (asavage@iname.com).)

    When I was working on printers, we'd see a few of the 600s in with corrosion on the ribbon cable end under the printhead. NewKote apparently had a venting problem with their copykat ink cartridges, where in some situations ink would spurt (leak? drip?) and somehow corrode the ribbon cable.

    I never tried to replace one and see if it could actually be repaired with just the cable, but I did try vigorously cleaning the cable end: no conclusive repair.

    BJC 600 print head error - lights flashing

    "Upon powering up the printer the two lights flash indicating a print head error. However by cleaning the electrical contacts (with alcohol) on both the print head and the printer the printer works,,, temporarily. Within a day or two the problem resurfaces. When the printer does print it prints excellent quality. The nozzles seem to be is good working order."

    (From: Al Savage (asavage@iname.com).)

    Although printhead failures are common on the 600 series, so is failure of the ribbon cable to the printhead. This is an acknowledged problem from Canon, when aftermarket ink reservoirs are used (i.e. Pirana or NewKote). Somehow the ink gets up to the cable/printhead interface and corrodes it. When I was working on them (about 18 months ago) Canon and NewKote were pointing fingers at each other. It appeared to be a reservoir venting problem.

    Epson Stylus Color IIS error light problems

    "The error light on the Epson Stylus color IIs keeps blinking. The color cartridge is new. The black and white prints perfect."

    (From: Robert J. Brancatelli (bronco@mkol2.dseg.ti.com).)

    Most likely, the new color cartridge is not seating all the way. Move the print head to where you normally do to swap the heads. Now, without removing the color print head, lift the most forward lever up as far as it will go, then bring it down to reseat the ink cartridge.

    Cleaning totally clogged colour head in Epson Stylus Color 500

    (From: Colin Guillas (rguillas@nrn1.nrcan.gc.ca).)

    I have an Epson Stylus Colour II printer which had similar problems- this time, which the magenta head.

    After running about 50 cleaning cycles, and having no improvement, I disassembled the unit (I am WAY out of warranty already ;-) and manually mopped out the cleaning apparatus- the rubber heads were VERY gummed up, so I wipe them off... the suction tubes were clogged, so I squeezed them out, the sponges were full, so I mopped them up with a kleenex. I then put on a pair of elbow length kleenex gloves, and pulled the cotton cleaning tray/absorbent reservoir out of the base of the unit, and rung it out into the toilet. There was a three year accumulation of wasted ink in there- this printer gets extremely heavy use, but it was amazing at the amount of ink that gets wasted, compared to what goes on paper! I would guess that it's about 30/70, 70% ending up on paper. Incredible wastage. I just don't buy cheap refills. I buy better ones with guarantees on them. I also replace the cartridges that I am refilling every four to six refills. There will be an accumulation of 'junk' if you don't.

    The cure to my problem? Pay the price for the genuine epson cartridge and do another fifty cleaning cycles. It worked for me. I had to wring out that @#$%liner again....

    (BTW, If anyone else has an epson inkjet, I recommend that they get the liner replaced or at least wrung out. It's a horrible mess which can overflow if you use an awful lot of ink... mine was saturated... you may have a nasty surprise next time you decide to move the printer- all down the front of your shirt. ;-)

    Epson Stylus 800 print quality

    "I have an Epson Stylus 800 printer which is only used infrequently. I seem to have a problem with some of the jets clogging up after a while producing a banding effect and/or a blurring of text.

    The built in cleaning cycle does not clear the problem. Running the head over a pad soaked in Isopropyl Alcohol clears the problem, but after a week or so things start getting bad again.

    The user manual does not mention the need to change any cleaning pads. How does the cleaning cycle work and are there any checks or adjustments which might improve things?"

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    Inkjet printers do not like 'infrequent' use. They need to be 'exercised' every once and a while. Use 'em or loose 'em!

    I'm not familiar with the Epson products, but on the HP DeskJets, there is a little rubber "seat" that the cartridge sits on when it is 'parked'. If it is gummed-up or damaged, it can cause the cartridge to slowly dry out.

    The HP's have a little oval-shaped rubber 'do-hikey' that seals the area around the ink jets. It generally gets gummed up with dry ink, and does not seal completely anymore.

    Check and see if there is something similar that covers the print head when it is not in use.

    The "banding" can also occur as the cartridge starts getting towards the end of it's life. Also try cleaning the contact areas with a soft cloth. Poor contacts can cause similar problems.

    If large ink droplets are forming on the head during printing, this is a sign of poor contacts or a physically damaged head.

    However, most of the time it is caused by "clots" in the areas supplying the jets, or in the jets themselves. Sometimes soaking the jets in a tray of alcohol or water for a while can dissolve these "clots", but the success rate is not that great. Better to fix the root of the problem.

    BTW: Avoid turning the cartridge upside-down. Always hold it so gravity pulls the ink down to the jets and keeps them primed. Turning it upside-down can allow air to be drawn back into the jets.

    Then again, it may be time for a new cartridge!

    Epson Stylus Color 800 printer seems to operate but no printing

    (From: Al Savage (asavage@iname.com).)

    Sorry to be the bearer of bad news, but the both the purge pump and the printhead in the Stylus series (300, 400, 800, ColorII) are very trouble prone. I've scrapped a couple dozen of them. The cost of a replacement printhead is more than the printer on sale.

    They do print nicely when they're working, though. My experience is that they don't work for very long.

    Epson Stylus Color 800 clogged print head

    (From: Alan G. Pope (agpope@phonetech.com).)

    PROBLEM: Dryed black ink clog-up in the tube leading from the black ink cartridge to the print head. Black ink flow totally halted. New cartridges won't work.

    BACKGROUND: Epson uses very fast-drying, water-soluble, inks in this printer, and if the printer sits idle for some length of time the ink feed tubes and the print heads become clogged with dry ink. Epson issues dire warnings about potential damage to the printer if attempts are made to flush these parts with any solvent, and recommends factory repair only.

    On the advice of someone who has vast experience with such problems, I successfully used the following repair. procedure.

    REPAIR PROCEDURE: Use a clean small hypodermic syringe with NO needle. Press on to the syringe nozzle, a 3/4 inch long piece of model airplane gas engine fuel tubing. This tubing is available cheaply from your local model hobby shop. It is a pale light blue colored plastic tubing. The MEDIUM size is the right one. The bore (ID) of the tubing is less than 1/16 of an inch. It makes a very tight fit when pushed onto the syringe nozzle.

    Remove the cartridge from the printer, and pull the power plug immediately to prevent any further printer movement.

    Load the syringe with 2-3 CC's of scalding hot water, preferably distilled water available at your grocery store. Then press the other end of the tubing down over the little black nozzle in the bottom of the cartridge holder. It must be a very tight fit.

    Forcibly inject the hot water into the printer. If the clogging is really severe, you may have to press the syringe plunger very hard. Continue injecting until the syringe is empty, while making sure that the tubing does not slip off the syringe or the printer nozzle. Repeat this injection procedure 1-2 more times with more hot water if necessary.

    Once the hot water goes through easily, the clog has been dissolved. It may be necessary to wait 24 hours for the water to evaporate, but in my case it was not. I simply replaced the black ink cartridge, and ran the Epson's head-cleaning utility several times until the black ink started coming through. Running the nozzle-check utility, to make a test pattern print, will let you know when the ink flow is OK.

    This same procedure should work equally well for the colored inks of this printer. I suspect that the procedure will also probably work for some other Epson inkjet printers as well.

    Use this procedure at your own risk. All I can tell you is that it worked beautifully for me. There was NO printer damage.

    Non-use and refill of BJC-620 ink cartridges

    (From: Roy (royf@iname.com).)

    The people who talk about clogging, etc. must have never seen a BJC-620, in which the printhead and ink tanks are separate. I've had a 620 for about 16 months and having printed almost nothing on it (have a laser for most needs) have noticed that the ink tanks last about 5 months. My third set of cartridges at $40 per set have just recently gone dry. (Actually only the color ones are dry. The larger black one lasts longer.) I foolishly threw away the first set of empties, but I still have two sets. I decided that I've sent enough money to Canon and searched the web for a more economical solution. What I found was Bob Nedved and his re.ink.kit refill kit at:

  • Re Ink Kit Home Page.

    where, for $74.50 I got an amount of bulk ink equivalent to about $800 worth of new cartridges. Included also are 4 syringes and 4 small screws. The procedure is to make a small hole in each tank tank and seal it with a screw. To refill, you remove the screw, inject a few cc of ink, replace the screw, and clean the syringe with a little alcohol or distilled water. Filling the first cartridge was a little messy, but once you get the hang of it, it's a snap. The kit doesn't completely eliminate buying new tanks, because the tanks themselves eventually need to be replaced, but it sure does cut the annual maintenance cost, whether you only use the printer a little or if you use it a lot.

    (From: Bill Sloman (sloman@sci.kun.nl).)

    Epson uses a piezo-electric print head, and an alcohol-based ink. If you don't like paying for Epson's ink cartridges, use Pelikan's (I think that is the brand I use - it is certainly one of the old-fashioned ink manufacturers). They seem to use a higher molecular weight alcohol than Epson, so the cartridges last me more like six months than three in the old (1993) Epson Stylus Q800.

    HP and Canon use a water-based ink, that is actually heated to boiling in the print-head to spit out droplets - so the print head corrodes rapidly, which is why their "ink cartridges" contain an new print-head and only about 15 ml ink, as much as the print-head can reliably spit out.

    Inkjet Printer Cartridge Type and Reliability

    Here are a couple of opinions. (From: Al Savage (asavage@iname.com).)

    Having worked at Epson, Canon, and HP warranty service centers, I tell anyone who asks me for advice about buying an ink jet printer to always choose one where getting more ink also gets you a fresh printhead. The number one service problem with all inkjets is printhead clogging failures. On the Stylus 800 series, for example, the printhead retail cost was $170, and the labor was about half an hour. On the Canon BJC-600, the P/H cost was $250, but the head could be changed by the owner. And with so many folks using third party ink that works like it was brewed up in someone's bathtub (NuKote, Piranha (sp?), etc.), printhead failures scrapped more inkjets than any other three causes combined.

    Cheap, owner-replaceable printheads help keep cheap inkjet printers out of the landfill.

    (From: Roger Hamlett (roger@ttelmah.demon.co.uk).)

    I disagree with the comments about chosing one where getting ink gets you a printhead. I have a bin full of 'dead' HP cartridges, that have resisted various attempts to get them printing again, yet also have an Epson here, that is four years old, and has never given any problems. The bill for cartridges on the HP, (allowing for the part use), would have paid to replace the printer a couple of times over.

    Ink cartridge expiration dates

    (From: Paul Weber (webpa@aol.com).)

    One other thing about HP inkjet printers (DJ 550, 560, 850): Before you buy an ink cartridge, look at the expiration date on the box. Don't buy it unless you expect to use it before the printed date. That number really means that the cartridge will NOT work after the date...no matter how it is stored. Water and/or hot water rejuvenation rarely works on cartridges that are outdated. The reservoir evidently turns to crap and won't wick the water in or the ink out.

    Dead Cannon, Compaq, HP, and similar power supplies

    Apparently, these power supplies may blow their internal fuse either as a result of an overload, or possibly for no reason at all. In this case, a new fuse will be all that is needed. Of course, it's also possible that there is a fault in the power supply or in the printer which will cause the new fuse to blow but it's worth trying a new fuse before more complex troubleshooting.

    (From: Jim Steel (procomputer@telisphere.com).)

    Repair instructions.

    The power supply is encased in a bonded 2-piece ABS plastic housing. There is a fuse inside but no way to access the fuse without splitting the case.

    Splitting the case:

    Unplug the power supply and secure the power supply in a utility vice. Use a short-blade utility knife or linoleum knife to slowly and carefully and cut along the seam where the 2 halves of the power supply are joined. Don't try to cut the seam all at once. Work a little at a time until the case halves can be separated.

    Replacing the fuse:

    On a power supply with an unsoldered fuse socket, simply replace the fuse and test the power supply. Alternately, a leaded fuse may be soldered in.

    On a power supply with the fuse soldered into the fuse socket, leave the fuse in the socket and solder in a leaded fuse. (A leaded fuse has lead wires extending from each end of the fuse.)

    On a power supply with a leaded fuse, unsolder the old fuse solder in a new leaded fuse.

    Testing the power supply:

    Ensure that the power supply and printer work before bothering to close the case.

    Closing the case:

    ABS plastic cement may be used to bond the power supply case halves. Alternately, electrical tape may be used to hold the case halves together.



  • Back to Printer/Copier/Fax Repair FAQ Table of Contents.

    Laser Printers

    Note: also see the chapter on Photocopiers as the operation and problems of the two types of equipment are very similar.

    On-line laser printer resources

    Warnings about vacuuming laser printer toner

    This is less likely to be something you would do in a big way with a laser printer compared to an office copier but if you are contemplating it, see the section: Warnings about vacuuming copier toner. There are several considerations including the risk of explosion and/or fire.

    Refilling toner cartridges

    If you can stand the mess, refilling some types of laser printer (and photocopier) cartridges can be worthwhile IFF the basic mechanism and photosensitive drum are in good condition. Even if you only get one more use out of a cartridge, the savings can be substantial. I have had mixed results buying reconditioned cartridges, but you know what your own have been doing in their spare time! However, it isn't quite just a matter of dumping new toner into a used cartridge:

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    Firstly the health/safety warning. Toner, because it's a very fine powder, is (a) carcinogenic, and (b) explosive. However, provided you don't make clouds of the stuff, you should be OK. It can't be *that* harmful, as some photocopiers take 'loose' toner, and some printers have separate toner/drum/waste toner units.

    I've fixed mechanical problems on the SX and CX cartridges. I also once moved a good drum from an empty cartridge to an almost-new cartridge with a scored drum (don't ask...).

    There are 2 things you need to do to refill one - empty out the waste toner tank and (obviously) add some new toner.

    The SX cartridge is easy to dismantle. Unclip a little triangular plate on the side, pull out 4 plastic pegs, and the case comes off. The plastic bung for filling the toner tank is obvious. To empty the waste toner, you have to take the cartridge apart, remove a plate (2 screws) and empty the toner into something. I worked inside a plastic bag last time I opened one of these cartridges.

    These printers use a combined toner and developer. The toner mix must be magnetic for the printer to work at all.

    I've seen bottles of loose toner for some photocopiers. I have not idea which brands would be suitable (if any), but I might experiment sometime.

    As for inspection/testing:

    Well, the main test is probably drum sensitivity (but this won't change unless you are swaping drums). Now, if you get that wrong, all that happens is that the image is too light or too dark. There are some little plastic clips on the side of the cartridge that operate microswitches in the printer. And there are only 3 settings!. Believe it or not, I've found some remanufactured cartridges that work better when these blocks have been moved - in other words, the drum sensitivity wasn't checked properly.

    Everything else should be mechanical inspection - condition of bearings/gears, leaks, primary corona, etc. Nothing that's impossible to do at home. Of course it's rather different if you're selling remanufactured cartridges - in that case you need to be sure the parts will last another 4000 pages or whatever. But if you're fixing up your own printer, and don't care if you have to fiddle with something else in 1000 pages time, then there's no real problem.

    About the worse that can happen to the printer is that the cartridge dumps toner all over the insides. I've had that happen - once. And it wasn't from a cartridge that I'd had in bits. It was from a remanufactured cartridge. That, together with the incident where a CX cartridge had had the door assembly incorrectly assembled, which caused damage to the transfer corona assembly, convinced me to avoid remanufactured cartridges that I'd not rebuilt myself, or at least checked.

    You do need to avoid mixing waste toner (which will probably have a higher concentration of developer) with the new toner. Empty out the waste toner tank, but don't add the contents to the new toner. But if the toner you are adding is similar (or better still the same) as the original stuff, there is no problem from the residual toner in the cartridge.

    Plenty of printers (Ricoh engine?) use 'loose' toner + drum/belt as separate parts. In those, you do add new toner on top of the old, and it all mixes up. Now, why should Canon printers be so different?

    Cleaning laser printer optical path

    As noted below, the optics are delicate and easily damaged. Use an air bulb to first blow off any loose dust/toner. Then use isopropyl alcohol and a cotton swab or lens tissue to *gently* clean the exposed surfaces. DO NOT disassemble any optics components - the alignment may be critical.

    (From: David H. (textool@aol.com).)

    It's always a good idea to clean the entire optical path from the laser (diode) forward. Most of this is inside the scanner module and there may also be a long external mirror.

    With time these surfaces become coated with a film of toner/dirt and the laser beam reaching the drum gets weaker and diffused. Print quality suffers and later "beam detect" or "scanner failure" errors will occur, which may be intermittent at first, but eventually they will shut the printer down completely.

    So open up the scanner module and gently clean all the prisms, mirrors and lenses. I say gently because the mirrors are front coated and the lenses may be plastic which can be scratched by aggressive cleaning with cotton swabs. Clean the external mirror if there is one. There is also a beam detection sensor which will have it's own small lens or prism which must be cleaned. Good luck.

    In my experience dirty optics has been the they most common failure in 4+ year old laser printers with Canon engines.

    Laser printer drum damaged by extended exposure to light?

    (From: DenFrodo (denfrodo@aol.com).)

    Yes, with extended exposure. I remanufacture toner cartridges for a time. Long term exposure to light will effect the photoconductive layer. We even cover areas of some (scratched) after-market drums and exposed them to sunlight to see how it effected them. It takes extended exposure to show an effect. No, the printer will not detect the problem and the printer will probably print dark for the basic 'positive' image (a dark area is exposed to light) laser printer. A scanner or copier might print light (reflective light of the 'white' surface exposes the surface of the drum. Good Luck.

    Repeating images on laser printer

    This likely means a faint ghost of the main printout at a distance equal to the circumference of one of the rollers or photosensitive drum.

    Depending on where the problem originates, this could be a bad wiper (cleaning) blade, faulty corona, or incomplete fusing.

    It is easy to determine where the problem is located: Interrupt a printout in mid-stride (where part of the paper is between the toner/developer and fuser. If the un-fused image has ghosting, it is a fault in the area of the drum. Also see the section: Previous copy doesn't erase from drum.

    Black evenly spaced lines on laser printer or copier

    (From: Edward Klotz (eklotz@www.flash.net).)

    90% of the time it is the toner cartridge (or drum), If it is still exactly the same condition with the new cartridge, here is one exception: The fuser assembly has a rubber roller, I had one with an indentation in one spot, allowing toner to pack in the indentation & actually transfer a small character impression onto the fuser roller and then transfer it to the paper several times on each sheet. The fuser is very easy to remove(2 screws at the back). I temporarily worked the indent out of the soft rubber, but eventually replaced the fuser assembly.

    (From: Dave Lee (leedj@uwec.edu).)

    According to "Image Defects, Repetitive image defect ruler in LJ4", the cause would me the "Primary Charging Roller", is 1.5 inches or 38 mm around. Start with that, swap with another printer is possible, or order one, try Parts Now, Inc, 800/886-6688 or The Printer Works, 800/235-6116 or Global Printer Service, 800/588-3554.

    Optics disassembly?

    "I would like to remove the mirror in order to clean it well. It mounts on a plastic bar that runs the width of the printer. The bar mounts by screws (2) at either end. I am worried that I will need some kind of aligning jig to get it back properly."

    The short answer is: DON'T. Some aspects of the alignment are impossible to adjust/correct/reinstall without factory jigs and test equipment. The best you can hope for at home is trial-and-error. Most of the optics is probably solidly glued in place anyhow so disassembly is difficult or impossible - but it doesn't move much either! The long mirror itself is probably less critical than the rest but there is no real need to disturb it.

    To clean the optics, use (low pressure) compressed air, alcohol and lens tissue, or as a last resort, alcohol and cotton swabs (Q-tips). However, some lens and mirror coatings may be easily damaged - test in a corner first.

    (From: Pete (PTCull@lbl.gov).)

    You are correct in being worried. Alignment marks closest to the muffin fan side of the engine should be noted before removal of the Beam-to-Drum Assembly. Better yet, just blow the mirror clean with a filtered compressed air source, leaving the mirror mounted.

    Unless the mirror is very contaminated, I really wonder if you'll see the improvement you believe you might? Some of these mirrors have very soft surfaces and only should be touched with lens cleaner or cotton swabs.

    If you still choose to remove the mirror from the engine, check to see if the two extreme sides of the page seem even when referenced to the top edge, using the "Engine Test print".

    HP LaserJet FAQ

    If your problem is with an HP LaserJet, before reading further, check the following three sources of information:

    Testing the erase lamps on an HP LaserJets

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    There's a very quick test for the erase lamps in these printers (SX engine). Open the cover, and swing it right open. There's a plastic post that comes down from the cover at the back left with 2 contacts in it. It goes into a slot on the left side of the fuser when the printer is closed.

    Check for continuity between the 2 contacts in the cover. I have no idea what the right resistance would be, but it's less than 1k. If it's open-circuit then most likely one of the lamps is burnt out. There are 5 of them, in series.

    If the lamps are good and there are still erase lamp problems, then remove the fuser, take the cover off the left side of it (1 screw on top) and unscrew the PCB under it. Check the 2SD1414 power transistor Q331 on this board (it's the erase lamp driver). If that doesn't do it, check the components around it. R335 (1.8 Ohm) is the current sense resistor in Q331's emitter circuit, L331 is a filter choke in series with the lamp supply, and Q331 is a current sense transistor that removes the base drive from Q331 if the thing overcurrents.

    I suppose it could be a problem with the cable back to the DC controller or even the DC controller itself, but that's unlikely.

    If you've still not found the problem, though, post again and I'll think again.

    HP LaserJet error code 51

    "On self-test, pulls in paper, pauses, indicates "51 err." Then pulls paper through mechanism while "02 warming up" is displayed. Nothing prints, except for 2 horizontal black bars about an inch apart with grey in between them, about 1/3 from top of page. Since we stole this fair and square, and since we have a number of good (but _not_ laser printer) techs around, I'm wondering where we might dig. The book simply says error 51 means we should call HP service."

    (Note: In the discussion below, the specific cable and parts IDs may not match your model.)

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    It's called a 'beam detect error'. Let me explain what that means:

    The laser beam is reflected off a spinning hexagonal (I think) mirror, and scanned across the drum. At one end of the scan the laser is turned on, and the reflected beam hits a fixed mirror (not the drum) and is reflected down an optical fiber to a photodiode on the DC controller board. The electronics on that board detects the pulse from that photodiode and provides a sync signal for the data sent to the laser

    So the fault can be the laser, the scanner motor, assorted optical bits, the photodiode, or bits on the DC controller board. I think we can eliminate the motor for the moment, as that tends to give Error 52s.

    Look at the PrinterWorks Web site (http://www.printerworks.com/) for exploded diagrams. Also read the section: SAFETY since you will be inside the printer near high voltage and possible exposure to laser light.

    The official fix is to replace the scanner, the cables (electrical and fiber optic) between the scanner and the DC controller, and then the DC controller until the fault goes away. But you can often fix things

    Start by pulling the casing. Over the paper tray there's a flat black box. Start be reseating the 2 cables (one under the flap) that go to this unit.

    If you have an IR detector (as used for testing remote controls) then undo the screw on the scanner - not the fixing screws that hold the scanner in place - remove the grey optical fiber, and hold the sensor over the channel that the fiber fitted in to. Do not look up this channel - it can output laser light. Turn on, and try to print a test page - which will fail.

    If you get IR light out of the scanner unit:

    Reconnect the fiber at that end, remove the base of the printer, and arrange some way to prop it upright with the interlock switch pressed in. Unplug the fiber from J201 (a DNP-like connector) on the DC controller board. Put your IR sensor on the end of that and test again. No IR light now, time to replace the fiber.

    Reconnect the fiber to J201 and hook a logic probe or 'scope to TP208 on the DC controller. This is the output of the photodiode amplifier. Do you get pulses here? If not, check the photodiode and the transistors Q202, Q204, Q208. If you do, then, alas the problem is most likely in a custom chip, and it's time to replace the DC controller.

    If you get no light from the scanner, then it's time to inspect it:

    Carefully trim back the moulded clips that hold the cover on the scanner and open it up. Clean the optics with a soft brush or lens tissue. The mirrors are front-silvered of course. There's a little shutter in the laser beam, opened when a toner cartridge is locked in place - is this opening correctly when you close the printer? If not, find out why not.

    Unplug the cable from the laser PCB, power up the printer and try a test page. Does the scanner motor rotate? If not, we'll debug that.

    The last possibility is that the laser isn't coming on for some reason. Debugging that is going to be interesting (read Sam's laser diode notes next :-), and I'll do the same) and I'll try to talk you through that when I know it's necessary. (Note: Sam's laser diode notes -- Diode Laser chapter of Sam's Laser FAQ.)

    (From: Tom Dunn (dunnt@cco.caltech.edu).)

    Error code 51 indicates loss of laser beam for over 2 seconds. Check -5 V, also make sure there is no interlock mechanism damage, and +5 V at J451-1 on Laser Drive PCA. You may need new laser unit. Good hunting.

    (From: John Holcepl (john_holcepl@nls.net).)

    This is a very common error on a HP Series II. An error code 51 is loss of beam detect. The cause is a bad cable between the DC Controller and the laser/scanner assy. P/N RG1-0908-000CN. Sometimes just reseating the cable will make this error go away but it will come back eventually.

    (From: Eric Liber (liberes@westinghouse.com).)

    Here is the description of the possible 51 errors:

    51 ERROR (Loss of Beam Detect)

    HP LaserJet I fuser swapping and other tidbits

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    What you need to do (if you're going to remove the whole assembly) is to remove the (brown) cover that's flat on the printer chassis just behind the 'tower' at the front that contains the interlock switch and AC control boards (where you removed the fuser heater wires from). Under that cover there's a little 4-way connector that links the fuser thermistor back to the engine control PCB (DC controller). Unplug that.

    Then you can remove the 4 screws that hold the fuser in place, lift it up a bit, and free the heater wiring from the channel in the baseplate. The whole fuser then comes out.

    These fusers can be stripped and rebuilt - I've done it. If the old one still heats up, keep it for the heater lamp that's in it - that lamp does fail, and it's not that hard to replace. It's a quartz-halogen bulb, so you shouldn't touch the 'glass'. The safest place to store it is in the old fuser.

    These printers are that bad. I've had one stripped down to individual components (even dismantled the optical assembly), and have it running now. But the SX engine (LJ2, etc) are a lot easier to dismantle into modules (and in some cases harder to replace individual components on...)

    HP LJ Series II bad bearing noise and other comments

    "Got one that started making unpleasant noises about two weeks ago. It is in a church office environment, so they have to turn it off unless they need it for a short while. I took part of the cover off and decided it wasn't the top fan or the small motor on the right side. The sound comes from the right rear at the grilles at the bottom of the machine. It sounds like a bad bearing or something rubbing a fan."

    (From: Ralph Wade Phillips (ralphp@techie.com).)

    Bad lower fan. Part number RH7-1056. I'd check at http://www.pcservice.com and register and order XX-RH7-1056 (it's under $20) and just replace that fan.

    I'd also consider replacing the upper fan (go look for it with the search engine - it's about the same $ for the generic 3rd party version) since a failure there will ALSO cost you the fuser gears, thereby costing a fuser assembly.

    As to removing the bottom cover - Eh? Put the top back on, flip it over, and remove those screws you see around the rim. Remove all cartridges also. Slip the metal cover off, and viola - There she is!

    Big warning - Do NOT run the machine with the lower fan disconnected. This is known to damage the DC controller board (at least a $60 part, EXCHANGE - over $300 purchase!), and can cause massive problems later down the road ... Take a look at http://www.printerworks.com and look (and print, if possible!) their exploded parts diagrams. Yes, books are available, but will outrun the $150 the church is paying for it (worth it, though, with as many LJ2/LJ3/QMS/LWII and other SX-based printers out there, IMAO.)

    (From: Al Savage (asavage@iname.com).) Probably the most-commonly-replaced part is the lower fan on the 33440A. Yes, it's very noisy when bad, right up until it becomes extremely quiet .

    Well, buying 10 year old hardware and then wanting to depend on it not breaking isn't very realistic. As reliable as the LJII/III is, they DO break, especially lower fans, the 14T fuser gear, paper pickup roller, pickup photosensor, AC power supply, registration assy. It's just that they'll commonly print half a million pages in the process, and many contemporary printers aren't designed for a service life a third as long.

    To replace the lower fan, have a vacuum cleaner with a brush handy (or an air compressor). Remove toner cartridge/drum unit. Close lid, remove all cables (power, data), flip printer upside down. On a LJII, you're looking at steel square pan; on a LJIII, you're looking at a large plastic tray and you have to remove four Phillips-head screws to get it off first.

    On both models: remove any optional memory card(s) by first removing the access hatch for them on the left side. This hatch is the one *without* the 1/4" hole in it. Remove any circuit board you find under there: they just pull straight out.

    On the back of the printer, remove any optional I/O card (HP JetDirect, Appletalk, etc) that may be installed next to the normal Centronics data port. This isn't always *necessary* but when it isn't it just makes things easier. Once again, just remove two screws and pull on the I/O card.

    Now you can remove the lower pan. Nine Phillips head screws later, lift the front edge of the pan, wiggle it to get it off over the Centronics port cable clips.

    Vacuum the pan out -- it will be filled with dust bunnies -- and any dust you see collected on the mainboard. You can now see the lower fan. It's a squirrel cage design. Remove the short wire harness and the four screws to remove it. Note the position of the small bracket under two of the screws, as you will need to put that bracket back!

    Reassemble in reverse order. One screw on the lower pan does NOT go in the left rear corner, but that's only a problem is you have the upper plastic off as well. You can't put it in wrong if the upper half is still assembled.

    The fan is about $20 wholesale, often close to $40 retail. Do NOT attempt to disassemble and clean it. I've tried several times, and no matter what I try it will either still be noisy, or will fail again within months.

    HP LaserJet II just dies and no sign of power after a short while

    (From: Larry Sabo (sabo@storm.ca).)
    "I have an HP LaserJet II that will just die after a short time. There are no power lights, not even an error message. If I leave it for a short time it will come back on after a power cycle. It is totally random."

    Check the daughter board in the PSU at fault. On mine it had deteriorated solder connections on *both* ends of the connecting pins. Remove it, resolder the pins on the daughter board, then remount it. It's worked like a charm ever since.

    HP LaserJet II with dark bands on first page

    (Problem and solution from: Ken Eckert (eckert@sfu.ca).)

    I have a LJ II that has the following problem:

    "The problem is a dark horizontal band starting at line 1, about 1/2" wide, indistinct edges. Repeats down the page at same length as the optical drum circumference. Problem is present only on page 1 of a print job. All other pages are clean. When the engine is stopped at the beginning of the print process a large amount of toner is present on the OPC in a band. Band gets darker and larger the more time between successive print jobs is incurred.

    Swapping cartridges has no effect."

    The problem turned out to be the chassis wiring harness from the DCA controller to the HV module. There was a bad connection between the HV module and the chassis connector only when the module was inserted. I ended up extracting and soldering all the crimped pins in the connector. I suspect that it was probably the HV reset line that was the problem.

    HP LaserJet II output jam

    "I found a junked HP Laserjet II which initially jammed pulling in the paper. I have fixed that. It still jams on the output, though. It prints nicely, so it seems worth fixing. If I open the back tray, the sheet exits 90% before stopping with the "paper jam" error. With that tray closed, I get the accordion paper jam in the fuser area. I do not detect any rotation of the upper rollers to feed the paper out of the top. When opened, I can roll them by hand easily. I see no obvious gear wear or broken teeth. I also see deep scratches in the grey fuser, which is probably unrelated. The toner does not have any fusing problem that I see in a band down the page."

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    I think you've got 2 problems here - the false paper jam with the tray open, and a problem with the drive to the top rollers.

    Let's look a them in that order.

    There's only one paper sensor in the SX engine that I know about, and that's part of the fuser. On the PCB at the left side of the fuser there's a slotted opto-switch with a lever that detects paper in the fuser. There's also a single transistor on said PCB that buffers/amplifies the output from the opto-switch, Q332, I think. This sensor must change state one way (to indicate paper has got to the fuser) shortly after the registration clutch operates and then change state the other way when the paper has got out of the fuser.

    You might start by reseating the cable at J206 of the DC controller board (just in case it's bad connections) and then look at the sensor (mechanically and electrically) on the fuser PCB.

    Silly question: If the paper tray switches (on the DC controller board) aren't operating properly, could the printer think it was feeding a shorter piece of paper than it actually has, and then give a paper jam error? It's always possible... Alas I don't know the coding for these 3 switches (SW201-SW203)

    The other problem is almost certainly mechanical. Look at the gears on the right hand side of the fuser (stripped teeth do occur here) and in the top cover of the printer. Shouldn't be too hard to find where the drive has failed. I suppose you could remove the outer casing and AC block, re-insert the fuser and close the cover, and look at things while turning the machine by hand.

    HP LaserJet IIp won't go past 'warm up'

    "I have an HP IIP that goes through the "05 Self Test" mode but hangs when it gets to "02 Warm Up." The only thing I ever hear run is the fan. I am not getting any error codes otherwise. If I try to send a print job to it in this state, it seems to take it and the On Line indicators light up, but it won't print. Based on what I've read in the FAQ and in the archives, I'm guessing it is the DC Controller. I re-seated the connections going to the DC controller PCB and the power supply and everything else visually looks good. I do not have a service manual for this unit.

    Can someone tell me how to test the DC controller to see if it is defective or maybe shed a little light on what may be causing the unit not to make it to the "ready" mode?"

    Any number of simple faults can result in the warmup sequence not completing. Check these first before suspecting a blown power supply or controller.

    It may indeed be as simple as a burned out bulb or broken door interlock.

    (From: Dave Lee (leedj@uwec.edu).)

    Here is what I found in my notes concerning your very same problem, Hope it helps......

    New "Service Today" from Parts Now, volume IV, number 1, issued in Feb 95 is devoted to the "LX" engine units, IIP/IIP Plus/IIIP Series, the Cannon LBP-4, Apple Personal LaserWriter. Lots of good stuff, error 50's, error 41's, fuser upgrades, "moaning", other squeaks etc.

    Here is what it says:

    If hung on "02 Warming Up", trouble may be caused by cables on the door wear and tear. Also look at DC Cnt PCA, dual I/O, formatter PCA. Now also look at the solenoid for the MP pickup roller assembly. This can cause the 'hung 02 Warming Up' error if an open occurs in either the solenoid cable, or solenoid coil. To check, remove the formatter PCA in order to access the DC Controller PCA. Locate J209 on the DC Controller; pins 1 & 2 are the solenoid. Measure across the top of these pins, the correct reading is 200 ohms +- 10%. Replace the paper path door cable assembly, Part #RG1-1608-000 if the solenoid has high resistance.

    (From: Jeff Churchvara (jeffc@pond.com).)

    Experience would have diagnosed this one in about 10 seconds. I just didn't know what I was looking at.

    I started reading the FAQ and figured the worst. At first, I did not have the service manual to go over this code. When I finally did get a copy, I started checking the voltages and did not have +24V at the DC Controller PCA.

    All of what I was reading said to defeat the door interlock. At first, this didn't make sense to me because the bar that should be attached to the door was instead, laying on top of the switch and wasn't even moving when the door opened. I didn't know enough not to look any further.

    Once I realized the bar should've been attached to the door, I started looking for it's correct mounting. The screw holding the bar must have loosened up and over time it broke the mounting nut right out of the door.

    I ended up resetting the nut (threaded sleeve) by adding a screw from the outside. Then I pinched it in place with a second screw when I re-anchored the bar. This made the bar pull away when the door opened and then correctly contact the interlock switch when the door closed.

    I forgot the basics of troubleshooting when I posted this one and was making it more difficult than it actually was.

    Thanks to all of you who responded and kept me looking in the right direction.

    Totally blank printout on laser printer or copier

    (From: Ed Paolo (edpaolo@intac.com).)

    Check to see if the image of the printout to be, is on the image drum. If it is there and isn't being transfered to the paper then something like the high voltage corona wire or hight voltage supply isn't charging the paper.

    (From: FAXFIXR (justdfax@cdepot.net).)

    There are two corona wires, the charge corona and the transfer corona. The charge corona is the one you should look at. It is located in the toner cartridge so the easiest way to check is try another cartridge, even one that is out (or almost) of toner. If you don't have another, then you can check yours. If you look at the cartridge in it's operating position, there is a black mylar plastic film that covers a slit on top from end to end. The mylar covers the corona wire but allows you to insert the little green tool, found inside the copier, to wipe the corona. If the tool is there, stick the pad into the slot and wipe it back and forth. If you hear a slight screeching sound (like a violin) then the corona is there. If it's not there, then the cartridge must be replaced.

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    (The following was written for HP LaserJet III but it is generally applicable to other laser printers and photocopiers.)

    For starters, try a new toner cartridge. I've found these can cause all sorts of problems...

    Now, blank pages are due to one or more of :

    1. The drum is not getting exposed by the laser
    2. The EHT power supply isn't transferring toner onto the drum
    3. The EHT power supply isn't transferring toner from the drum to the page.

    Start it printing a test page (the 'engine test' switch on the DC controller is useful for this). When the paper is still going through the printer, turn it off, open the lid and pull back the cover over the drum in the cartridge. Is there a 'latent image' on the drum? If so, check the EHT power supply and transfer corona assemblies.

    Check that you plugged the cables into the scanner properly. They don't always make good contact. This will normally cause a 'beam detect' problem - I forget what the error is for that (51? 52?). It's possible that there's an O/C in the cable, of course.

    If you have an IR detector (of the type used for testing remote controls), unplug the optical fibre from the DC controller and point the end at the IR detector. Again print a test page. If the laser and scanner are working, you'll get some IR (laser light, so take care) out of the end of the fibre.

    There is a mechanical shutter in front of the laser in the scanner that's opened by a lever under the scanner when the cover is closed with a toner cartridge in place. The idea is to prevent any laser light getting out if the printer is run with the cover open/no cartridge. Is this working correctly. Did you get the scanner correctly on top of it.

    Bearing replacement on HP LaserJet II to fix error code 41

    (From: Andreas Mohr (a.mohr@mailto.de).)

    My (donated) Laserjet II series printed black horizontal lines after about the third sheet. It then occasionally spit out "error 41".

    Solution:

    The ball bearings of the scanner unit were defective (now I know that my printer was MUCH louder than other HP 2s). That caused the scanner unit to get "out of sync" and print black lines and occasionally spit out "error 41".

    I just replaced the ball bearings and everything was fine again.

    As far as I know, no Laserjet error codes service page mentions this yet. (They only say that "the scanner unit may be defective", but not HOW that may be.)

    HP LaserJet series II - error code 50 Service and clicking

    (From: Peter Strezev (jup001@airmail.net).)

    I had a LaserJet series II with exactly the same symptoms: 50 SERVICE and that very clicking sound. I fixed that printer last week after quite a bit of troubleshooting.

    First: the clicking sound comes from a mechanical relay in the PSU, which controls, together with an SCR solid-state relay, the sequence in which power is applied to the heating lamp in the fuser. The sound itself is not a problem, it is a symptom. You probably have a bad thermistor in the fuser assembly, or the signal path from the thermistor to the control board is corrupted.

    If you are good with electronic troubleshooting, try the following:

    (From: Mark Wolfe (markw@wwa.com).)

    Just to speed things up a little, override the printer open switch, and remove the plastic cover from the right end of the fuser to get at the power connector for the bulb. Turn the thing on, and read this connector, should see about 115 VAC, if you don't, check Q101 in the Power Supply. The problem you had sounded like a rarity, as it's usually the halogen light in the fuser, or Q101 in the power supply. Yours was the sensors going back to control Q101. Anyway, if you ever have one of the power supplies opened, it looks as if HP intended this triac to fail with it's whimpy heat sink. Hope this helps.

    I had the same thing happen to me on a IID, check the connections on the fuser. I swapped fusers with my III, and both printers worked, swapped them back and both printers worked. The power connector on the right end of the fuser seemed a bit loose, could've had a bad connection. Anyway, IID is still going, and this was in august when I did this.

    (From: Chris Holmes (holmesc@sedgehill.lewisham.sch.uk).)

    I dont know if Error code 50 is the same as Service 50 on the HP Laserjet II but if it is you are in luck.

    I once had this and spent about an hour and a half stripping cleaning and reassembling it, and it worked! When I got back to civilisation I checked the manual. The official HP action for Service 50 is - switch off for 10 Mins!

    Still i'm sure the clean did it good.

    (From: Frank