Canon Pixma MP640

The Pixma MP640 is a fairly typical A4 inkjet mid-priced printer. It's a sensible buy, 5 separate inks so cartridges can be replaced individually. There is a single printhead - ideally it won't go wrong in the life of the printer - but of course if you got to this page it may have. Cartridges and printhead mount in a moving carriage. The carriage is driven back and forth by a motor which uses a cogwheel to engage the teeth on a carriage belt.

Using separate cartridges but a single printhead unit is a compromise. Five separate printheads would be better because only one would need replacing when the nozzles no longer performed properly. A new printhead in this case is a third to half the price of a new printer. Separating the printheads out tends to be for a different price class of printer - one meant for heavy workloads.

The printhead and cartridges are not shown here, they sit in the carriage but Canon don't necessarily class them as spares.

Printheads will inevitably fail from time to time, nozzles block. Blockages and failures are almost inevitable: we are dealing with nozzles a couple of microns across etched in silicon, a crystal of calcium or shell of an amoeba in the ink will block a nozzle so impure ink won't work well. Congealed ink from the outside will also cause a blockage.

Printheads are quite easily replaced; but costly. Before replacing the head try cleaning any contamination from its contact pads - but at this stage do not touch the printhead nozzles or even their plate.

The printheads have a great number of nozzles which must all be instructed when to operate. The signals are provided by the logic board and communicated via the flexible Flat Core Cable leading from the base of the printer to the carriage. After a great many operations the carriage cable wears out and the conductive paths get metal fatigue giving an unreliable connection. If a new printhead doesn't solve print problems then the cable may be suspect.

The other carriage drive part that commonly fails with prolonged use is the carriage belt, which frays and may eventually lose teeth. A common sign is that the alignment procedure never succeeds. In this case the belt and carriage cable are built into the carriage unit, so they are not available independently.

The Timing Slit Film stretches across the carriage path. It carries a series of fine optical markings which are sensed as the carriage travels providing the main logic with a count representing the carriage position. If the slit film is contaminated with ink then soaking and rubbing with water or perhaps Isopropyl alcohol may clean it adequately. Be cautious about any aggressive solvent - if the film is damaged the printer will give an error.

The carriage motor is a DC encoder type. They are usually reliable but the life is limited by that of the motor brushes and bearings. Motors will ultimately fail.

Spares Prices

Prices shown are from a US and a European website. Note that whilst the US website may have apparently low prices the minimum order is $100, there could be a substantial carriage fee and they may be trade only. Spares sites tend to have either a minimum order level, a minimum price or both. Even with web orders and substantial automation it isn't possible to get a part into and out of a bin for $0.19 - although if you want to debate that there is moreelsewhere on the site.

Search and Spares Intelligence

A historic problem with spares is that most of them wind up in the bin. These days it might be a recycling bin. Some things are likely to be wanted as spares but guessing which is difficult. Timing slit films get broken. carriage trailing cables fatigue and little DC motors ultimately fail.

Feedback on forums might be used to assess products. Manufacturers forums are uneven quality and tend to attract the dissatisfied rthere than any mass of comment.

Search results (from Google for instance) are broader and might be used to make decisions about stock-holding for spares.

Google was use to search for the parts listed, putting the product code complete with it's zeroes in string quotes to reduce the flack. Most of the parts listed here give scarcely any response on Google search. The baseline seems to be 8 results; there are 8 or 9 people listing all the parts for these printers in some way. Nobody ever asked for most of the parts; there is no real activity on real technician forums, just helpowl and manualowl fluffing their own feathers.

List Driven Sites

It is clear from the rather minimal page content that all sites are being populated from "common" lists. Three sites, one in Australia, one in Europe and one in the US have an entry for almost every part so we can presume their list is supplied by Canon. For instance they all use precisely the same phraseology: …

… and so forth.

Another source of information is the Canon Service Parts lists. These are findable as a PDF (and are what I used as the basis of the lists and pictures). There are quite a few of these scattered around the web so they come up in parts searches. There is discussion elsewhere on Canon and other manufacturers attitude to service information.We think (1) People should have information about things they have bought. (2) Manufacturers are unlikely to be able to suppress it if they try.

Another couple of sites are presumably taking feeds from these sources. They aren't using the same original feed because they are present in Google for some codes, not for others.

The idea that search results might indicate spares demand is superficially confirmed here; the timing slit film has some demand, the carriage motor a great deal. However the actual content of the sites gives the idea a bit of a knock; they aren't forums dealing with repairs they are almost all supposed spares sites attempting to sell parts. But most of these parts will never sell - so what are they doing?

Long Established Lists

QC1-6202 is just a boring helical spring with eyelets, like a dozen others in the printer. What is different is that it has a long compatibility list. A bit of examination shows it has previously made a "generic" computer parts feed provided by Etilize. There was no sign of any activity around it - sites which suggested recommending it to a friend never had any such recommendation or feedback. Forums don't mention it. Its a boring part, its just been around the block a bit. That seems to be confirmed by QK1-1500 which has even made Icecat.

The QK1-1500-000 carriage motor inspired Google to no less than 10 pages of returns including:

amazon.co.uk (ZAR Systems) £28.00, uk-computers.co.uk £14.12, idns.co.uk no-price, markit.eu/uk £17.70 deivery 4 weeks, notebookservice-online.de 42 euros (5-7 day), mival.ro 92.83 ron,

However we compile a list of parts found in UK distribution. QK1-1500 was not found in UK spares distribution raising a question where those suppliers are getting it - is there one ex-equipment unit on a shelf somewhere?. Or are they getting a feed that contains it and marking it up.

Curiously, the only item that shows a flicker in UK spares distribution in QM3-6316 which is listed but with no stock. Quite why the pressure rollers would be replaced eludes me - perhaps one sprang to bits and a roller got lost? Then the part got put in a list and has been there ever since.

In a simple situation the number of Google responses measures the distribution of a list - how widely copy-cat sites have scraped and pasted one anothers data. With printer parts it is possible to get 15,000 list entries wiithout any huuman ever showing an interest in the part as the various sites claiming to know about spares take feeds from distributors and copy one another.

Huge numbers of responses start to indicate some saliency - how likely it is that the part will ever be wanted.