Step By Step 16 - Preventative Maintenance

Originally published in Australian Personal Computer magazine.
Last modified 03-Dec-2011.


Preventative maintenance is about the most boring PC-related field out there. It might even beat out databases and accounting software, but nobody knows, because whenever we try the comparison we fall asleep. But it can save you a load of money and pain, and it's simple enough to do, so it's worth knowing.


Most things don't need to be dusted. This may sound like Standard Adolescent Argument Number 3, but it's true; the amount of dust sitting on a telephone or clock or hi-fi speaker is pretty much irrelevant to its operation, provided there's not so much that you can no longer locate the device in question.

Computers, however, are different. PCs continuously suck air through themselves for cooling, and a large portion of the dust from that air stays inside the computer. Or accumulates on the fan grille:


Now, dust is by and large nonconductive and can't get into delicate assemblies like hard drives - hard disks have little air filters and no throughflow ventilation - but it can and does form an insulative blanket on circuit boards.

Every chip in your computer radiates heat, and CPUs commonly radiate as much as a soldering iron. The more dust settles in your computer, the more trouble these chips will have getting rid of the heat. Overheated hardware can cause errors, or just plain stop working. And seriously dusty computers can also accumulate enough motherboard scunge that any new expansion cards get a lousy contact.

Computers with multiple case fans (generally a sucking fan at the front and the standard power supply fan blowing out at the back) inhale more dust, but the greater airflow blows more of it out the back as well, so they're not necessarily any dustier inside than single-fan units. If your computer has a dust filter over its front fan, that'll help a lot - but you do have to clean the filter periodically, or the front fan will end up doing nothing much. Adding a square of filter-foam to computers that lack one is a worthwhile preventative measure.

If you use an ioniser to keep dust out of the air, don't put it right next to your computer. Ionisers, by their nature, attract dust, and cause it to clump together and stick to the ioniser and everything near it. This keeps it out of your lungs and eyes, but can stick it all over the outside and inside of your PC.

Shifting it

The obvious choice for getting dust off electronic components is a vacuum cleaner, but this is not necessarily a great idea. Household vacuum cleaners are, for a start, much more powerful than is needed to de-dust a motherboard, and can and do suck loosely-socketed chips clean off the board and into the dust bag. Using the curtain setting, if available, can prevent this - but it's not the only problem.

Regular vacuum cleaners also accumulate static electricity - old-fashioned belt-drive ones do a pretty good imitation of a Van Der Graaf generator, but the fast-moving air inside the plastic tube is enough to put a decent charge on the business end of just about any vacuum cleaner. Static electricity is, generally speaking, A Bad Thing for computers.

Many chips aren't static sensitive at all, but the ones that are can be destroyed by a static discharge as small as 200 volts, which is way less than you can feel and not nearly enough to make hair and scurf start sticking noticeably to the vacuum cleaner tube. Static electricity is also why you shouldn't use feather or other hand dusters on your PC; late night TV advertised "dust magnet" dusters are an even worse idea, because they're made to carry around a big static charge.

Vacuum attachments
If you must use a vacuum cleaner on your computer, get one of these adaptor kits to avoid damage.

That said, it is possible to vacuum your computer. You can got to an electronics store and get one of those little $25 battery powered vacuum cleaners built for the purpose. These, however, don't actually work very well. Shop around a bit more and you can for the same money get an adaptor kit for your big vacuum cleaner, with a suction-reducing ventilated collar, a flexible tube and a variety of miniature nozzles. Australians can buy just such a kit from Jaycar Electronics - catalogue number XV-5060, $AU23.95. Leave the computer plugged in but turned off as you clean it, and touch the case metalwork periodically to ground yourself. Your hand close to the end of the nozzle will be sufficient to keep the static down.

The easy way

Air duster
Air duster is the simplest way to get dust out of computer gear.

A simpler way to get dust out of your computer is with compressed air. This does NOT mean a machine shop compressor that can run an air-spanner and will blast your CPU through the wall; you're looking for a gentler breeze. Electronics stores sell cans of "air duster" at less than $15 for enough to clean a dozen or so motherboards. Air duster is difluoroethane or tetrafluoroethane, a non-CFC gas which, depending on how much pressure you apply on the nozzle, will emerge at speeds from a gentle breeze to a hair-pinning blast. This, incidentally, makes air duster a quite serviceable practical joke prop.

Air duster is actually much the same stuff as freezer spray - it just has no feed tube in the can and a bigger nozzle. This means that using an air duster can upside down will produce a white blast that'll chill whatever it's aimed at to 70 degrees below zero pretty much immediately, and empty the can post haste. This is likely to be found somewhat less funny by anyone you try it on, but is useful if you don't have proper freezer spray to hand but need to hunt a thermal fault.

Resist the urge to blast-clean dirty PC fan blades with the air-duster; if you spin the fan up to a zillion RPM, you may well fry its electronics.

Mouse maintenance

The mouse is the one component if your computer that becomes obviously much more annoying to use when it's dirty. You can, however, significantly reduce the rate at which your mouse gets filthy. The key is to use a textured mousemat - one with a surface covered with tiny undulations. The idea is that the crud falls into the valleys and the ball only touches the ridges, as opposed to the approximately 90% rubbish transfer efficiency of the traditional fabric mat.

The first decent textured mat was 3M's Precise Mousing Surface, available here in Australia from better computer and office supply stores including, for some reason, Australia Post shops. The paper-thin 3M product is vulnerable to bending and gashes, though; hard plastic mats like those from Everglide or Ratpadz (I compare a couple of recent models here) will tolerate far more abuse.

Cigarettes are bad for computers, too

Smoke can, arguably, count as dust, because it includes zillions of tiny particles. Gunk from cigarette smoke, though, is considerably harder to get rid of than ordinary dust, thanks to the various sticky organic compounds that all those quit-smoking ads keep showing us. Smoke builds up on mouse balls and rollers, especially if you habitually hold your cigarette in your mousing hand. So don't do that.

Smoke particles are plenty big enough to interfere with the operation of hard drives, but the only air flow into and out of a hard drive is because of changes in temperature and atmospheric pressure, so there's no need to worry about your habit hurting your main hard drive.

Removable disk cartridge drives, though, are another story. Many have quite complex dust-exclusion systems, but smoke microparticulates can defeat them. If you can stand it, keep the cigarettes away from the computer. If you need a displacement activity, try not to make it drinking, since liquid spills are a much bigger hazard than smoke.


Most computer users know to keep floppy disks and other magnetic media, including hard drives, away from magnetic fields. And most of them know that speakers that aren't magnetically shielded, and magnetised screwdrivers, and magnetic paperclip holders, fall into this category. But the greatest threat to data comes from changing magnetic fields, not static ones. When you move a disk next to a magnetic object and then away again, the field strength across the disk changes, but it only does it once. A old fashioned bell-ringer telephone, on the other hand, contains a rapidly pulsing electromagnet to activate the ringer, which makes a much better disk-eraser.

Monitor degauss coils are the things that make the monitor make that "gonk" noise and the screen wiggle. They activate automatically when the monitor powers up, and are used to remove magnetic contamination of the tube assembly. They will also cheerfully degauss things left atop the monitor. And printers, especially older dot matrix models, frequently contain quite large and poorly magnetically shielded motors.

Clean power

I give power conditioning the full treatment in Step By Step 9; here's the executive summary.

Regular household power is afflicted by surges, spikes and dropouts. These can kill computer gear outright or, more commonly, just hasten the normal death from old age of power supply and other components. Ordinary hardware store surge/spike filters are of little value. A proper "line conditioner" with a dirty great transformer in it is much better. A Standby Power Supply (SPS) or Uninterruptible Power Supply (UPS) is better yet, because these not only iron out supply irregularities but can also keep you going through a blackout.


Radio Frequency Interference or RFI is, generally, much more of a problem for devices trying to coexist with computers than it is for the computers itself. Even with the case on, a regular PC will stuff up reception on any televisions with antennas less than several metres away. It is, however, not impossible for radio interference to corrupt data and cause other mysterious errors, and you might as well not tempt fate.

Do not run long computer cables next to long power cables - they should, ideally, cross at right angles, and as seldom as possible. And don't use monstrously long cables where short ones will do; longer cables have more loss and are thus more susceptible to interference. That said, all wires act as an antenna for radio frequencies with a wavelength four times their length. This means a 75 centimetre cable is well tuned to pick up 100 megahertz RFI. Bear this in mind if you live close to a major transmitter or other strong tuned RF source, and use cables shorter or longer than the magic length. But if you don't see strange data corruption or network errors, don't worry about it.

Printer maintenance

The printer is the biggest mechanical component in the average computer system, but it doesn't need as much maintenance as you might think.

Plug your printer into a power filter - a proper line conditioner, by preference, not just a spike/surge filter - see Step By Step 9.

Some somewhat grimy laser printer gears. They do not need cleaning, and they do not need oiling.

Resist the urge to oil your printer. If it uses plastic gears, oil won't make them work any better and may attack the plastic. If it uses metal gears, they probably aren't heavily enough loaded to need extra lubrication. If you must lubricate moving parts, do it with light grease - lithium grease is available at electronics stores, and does a good job - and be very sparing with the stuff, as grease in your paper path is a Bad Thing.

For most printer cleaning, the manufacturer-approved damp soft cloth is fine. If ink has found its way onto the paper guides and water won't shift it, you can swab it off with cotton buds and methylated spirits (denatured alcohol, for non-Commonwealth readers). Wiping the whole printer with meths or any other solvent is unnecessary.

When working on any inky printer - ink jet or dot matrix - use disposable gloves. Or don't, if you like that I've-been-writing-with-a-quill-pen blotchy-fingered look. Plastic gloves from a pharmacy are perfectly adequate, but you shouldn't use them when working on static sensitive devices. Latex surgical gloves are harder to find, but better. Plus, they make you look a lot more dangerous.

Do not use air duster to blow crud out of your printer, unless you're sure you'll actually be blowing the crud out, not deeper in. A light dusting of spilled toner in a laser printer is perfectly harmless, if it's not in the paper path. Even if it gets on the paper, as long as it's not before the paper's ironed by the fuser roller you'll just be able to blow the unfused toner off again. But if you assault the dust with a hundred mile an hour air blast, you may well squirt it right in onto the fuser itself, from which it can be rather difficult to remove.

Inkjets are easy

Inkjets (including Canon's "bubblejets") are largely maintenance-free these days. Many modern inkjet cartridges include the whole print head, which is why they're so expensive. Ink jet print heads, therefore, seldom get the chance to get dirty or block up.

So what if your cartridge does manage to block up - if you use the printer seldom, live somewhere rather dry and warm, or refill a cartridge over and over? Try trickling hot water over the nozzles, making sure not to touch the cartridge contacts. Dry the nozzles by just touching them with a paper towel and you may have a working cartridge again. Bear in mind, though, that many "clogged" ink jets don't actually have a blockage at all, but some other problem with the cartridge.

Dot matrix maintenance

Dot matrix printers are still popular with skinflints and those who need something that can print on multi-part forms. Many of these business printers are old warhorses with a lot of miles on them.

If your dot matrix is an essential component of your business, check how it moves its print head side-to-side. It's probably a belt drive. If so, get a spare belt now. That way you can just swap the new belt in yourself, or have it ready for the serviceman, if the old one snaps. There are many different belt sizes, and belts for older printers can be hard to find.

Dot matrix print heads run hot. Most of them have an impressive array of cooling fins. They most commonly fail when overheated - they're meant to shut down when they're too hot, but they don't always do it in time. So a borderline printer may be fine for any number of small documents, but die after 50 pages of your invaluable thesis.

Accordingly, dot matrix printers like a bit of air flow, and shouldn't be surrounded by stuff and/or positioned in direct sunlight.

"Refreshing" dot matrix printer ribbons with spray-on oil, canonically WD-40, is a fairly popular practice. It may or may not be a good idea, depending on who you ask. Dot matrix ink contains lubricants designed to grease up the print head and keep it working properly. WD-40 is a lousy lubricant, generally speaking - it's good at stopping squeaks, and it will make your ribbon print black again, but it may or may not be an adequate replacement for the original oil. Again, this is a problem which may only manifest when the printer's working hard - which is probably the exact time when you least want a print head to die.

The simple way to deal with a worn out dot matrix ribbon is to buy another one. The per-page print cost of dot matrixes is far below that of other printers, so you've got to be a pretty severe pennypincher not to want to replace the ribbon.

This would be a good point to mention that I am a pretty severe pennypincher - I must be, because I own a dot matrix ribbon re-inking machine, and several bottles of the greasy, evil ink. The re-inker paid for itself. After about five years. If I were you, I wouldn't bother.



Better laser printers, like this HP Laserjet, come with a cleaning brush and full instructions on how to use it.


The following paragraph both describes the operation of an ordinary laser printer, and mentions all the bits that can go wrong

In a laser printer, there's a photosensitive drum that's electrostatically charged to about minus 6000 volts by the "main corona wire". Light, usually from a laser, is shone on those parts of the drum that correspond to black on the printed page. The light causes the drum's charge to drop to around minus 100 volts. A roller then applies a layer of toner to the drum. The toner is repelled by the strong charge on the bits of drum not painted by the laser, so only the desired areas are still black when the drum rotates further. A positively charged "transfer corona wire" under the paper pulls the toner from the drum to the paper. The drum is wiped clean, its charge is neutralised by an eraser lamp and the process starts again, while the paper moves on through the heated "fuser rollers", which iron the toner onto the page. The fuser roller which comes into contact with the toner is also wiped clean, by a "fuser wand", which may be part of the cartridge along with the fuser itself or may be a separate component.

If your printer has a separate fuser, new cartridges probably come with a new fuser wand. It's possible for the wand to get dirty before the cartridge is out of toner. The scunge on a dirty wand can gouge the surface of the fuser and create vertical stripes on your printout.

Fortunately, you can easily remove built-up crud from a fuser wand by scraping it with a coin. Pluck off any fluff you've raised by scraping, and pop the wand back into the printer. Turn laser printers off a quarter hour or so before you crack the case and start fishing around, as the fuser rollers are hot enough to burn you when the printer's in operation.

Warning sticker
Laser printer heat warning stickers are not kidding.

Do not touch, or even look at, the photosensitive drum in your printer cartridges. It can be harmed by light and by the oils in your fingerprints. Most cartridges have a spring-loaded door over the drum; it's there for a reason. You CAN clean gunk off the drum by wiping it with a soft, dry, lint-free cloth; if you must, do it in dim light. You will probably never have to. Crud on your pages is probably the fault of dirty fuser rollers.

Generally speaking, if you're cleaning a laser printer and don't know what a component is, don't touch it. Briskly rubbing down a charge transfer roller can kill it.

Laser printers with a corona wire to charge the photosensitive drum are likely to have an ozone filter in them somewhere. Ozone is a health hazard; if there's a strong ozone smell around your printer, the ozone filter is probably clogged, which quite apart from the chance of lung damage also means your printer's not getting as much air flow as it would like. The filter may be part of the print cartridge; if so, just get a new cartridge.

You can get "cleaning paper" for laser printers, which aims to grab dust and toner from the guides and rollers inside the printer. Cleaning paper can do quite a good job, but it can't touch dust or toner that isn't presently on the paper-touching components - vibration and air movement can float this crud into the paper path right after cleaning. Some laser printers can print their own "cleaning page"; some do it automatically when you shut them down.

Some people have a morbid fear of laser printer or photocopier toner, believing it to be an incredibly deadly poison or carcinogen or some such. This fear is unwarranted. Toner is part plastic and part carbon, as a very fine powder. When it's heated, the plastic melts and can be ironed onto the paper by the printer's fuser, with the carbon providing the black colour. Neither the plastic or the carbon is a danger to humans, per se, except for the fact that fine powders are easy to inhale, and inhaling any fine powder is bad. Toner is no more dangerous than talcum powder; if you absent-mindedly blow into a spillage and get a face-full of the stuff, just try not to breathe it, bow to any spectators, and don't worry about turning into one big tumour overnight.

Toner can, however, be lethal. To vacuum cleaners. Do not vacuum up toner spills. Toner is so fine that it can pass through the pores in a vacuum cleaner bag, and it's specially designed to melt together when it gets hot, and it's full of conductive carbon. Vacuum cleaners keep their motors cool by letting the airflow blast straight through them. Can you see the problem here?

Sucking up a pile of toner will, at best, result in some of the toner being blown straight through the cleaner and all over the place, while the rest of it gums up the motor. At worst, your vacuum cleaner can catch fire.

Give Dan some money!
(and no-one gets hurt)