Canon Pixma MP640

The Canon PIXMA MP640 is an all-in-one printer combined with a scanner so that it can also act as a copier. The printer/copier can work without a computer, it has pictbridge for direct printing from cameras and slots for memory cards in the right hand side. To make non-computer use still easier it has little LEDs in the cartridges that flash to warn they are running out.

Most people will use the printer with a computer, it has USB, Wired Ethernet and WiFi. Other features that added value were the duplex print ability and the colour LCD control panel. The printer was on the market from 2009 to 2011; the official retail price was £179 but the street price was more like £135 (CPC Catalog 2010). The MP990 was launched at the same time, it is quite similar but with an extra grey ink, bigger LCD screen and CCD scanner - it shares quite a few parts.

These printers are moving towards the end of their intended design life. Canon probably wouldn't put a figure on that but we can; it is probably the life of one or two printheads at the most and rather clearly intended to come to an end when the ink absorber is full. Canon policy pushes you to an authorised service centre to get the absorber changed and they will probably want half the price on a new printer to do the job - the materials don't need to be expensive but it does take some time and Canon don't release the "Service Tool" sotware to reset the counter. When you get the "5B00 Ink Absorber Full" message you have a repair / replace decision to make.

Replace

People who have a dead printer aren't going to be entirely happy - but most inkjet printers have a low purchase cost (considering their complexity) and a rather short life. If you want to replace the printer and are happy with the Canon brand the PIXMA MG6450 (8333B008AA) is the direct replacement in early 2014.

Advantages of the newer printer are a smartphone ap for direct printing, "cloud print" and there are optional high yield inks. Disadvantages are that the screen is in a fixed position and some people won't like the rather dominant blackness - although it has won a design award.

Disadvantages of new printers generally are that they won't use the old inks (ink formulation may not change but the cartridge does). There will be the usual fiddle setting up the software (since the features are slightly different the driver changes). Recently there hasn't been much real design progress - there won't be a marked improvement in print quality.

Repair

Repairing inkjet printers is usually fairly easy, but you definitely need some technical knowledge. Most repairs also need the service tool to clear the relevant counter. Service Tool Software is probably available via eBay or as an unauthorised download but you need to know what you are doing (beware of downloads; they may be malware). Canon will give no support and to be honest we don't blame them - repair procedures are definitely not aimed at the average home user. (The absorber design is obtuse).

It will definitely help if you can get the service manual: it is called "MP640/MP648 Service Manual" and it has a part/document number QY8-13CN-000.

Cartridges

You are probably reading this because something went wrong. Prime suspect in any piece of technology is the last thing changed. In an inkjet printer that is usually the cartridges. The problem with inkjet printers is that the manufacturers ink is costly - a massive markup on the real price of liquid ink. However the original Equipment manufacturer (OEM) does generally get things right. Clone and refill ink manufacturers often don't get things right. If you want reliability, good colour balance, longevity in your prints - then use manufacturers original inks.

Printhead

When a printhead is giving streaky print that won't shift with cleaning or deep cleaning cycles it is too late to regret using cheap inks. But no printhead lasts forever. The question is - new printer or new printhead ?

Big printheads that handle four or five inks are expensive pieces of work. This is the piece of micro-engineering at the heart of an inkjet printer so perhaps it isn't surprising that they cost a third to a half the price of a whole new printer.

The rest of the printer has bulk, styling and even intelligence but it is essentially just a wrapping around that all-important printhead.

No special tool is needed to change a printhead, it just clips into place, then it needs the standard alignment procedure. Canon documentation speaks of them as "semi-permanent" which losely speaking means they will fail in use; cost quite a bit but aren't counted towards the cost of a page (like laser printer fusers).

Before spending money on a new printhead it is worth checking the contacts and seating on the old one, since a bad contact can cause streaks quite like those from a blocked nozzle. See the section on carriage faults as well.

Ink Absorber

The thing that usually kills inkjets is the absorber.   Inkjet printers need to clean out their nozzles from time to time otherwise congealed ink will dry inside them. Printers do this by periodically firing the nozzles then wiping the surplus off the head.

Unless the user guide says otherwise we recommend leaving inkjet printers switched on at the wall. The processor in the printer is likely to periodically go through this head-cleaning cycle for a few seconds - which can be disconcerting when they do it unexpectedly and you thought the printer was off! The printer may waste a couple of watts of power, but most power-supplies are pretty efficient these days so the cost of power will be negligible. It wastes a little ink, but far less than trying to recover from dried nozzles. It's less expensive than the price of a new printhead.

Used ink accumulates in absorber pads in the bottom of the printer. Americans tend to call the pads a "blotter" which is possibly a better name.

Professional quality printers have exchangeable waste ink tanks. Smaller printers don't, they meraly use the bottom of the printer as a tank. They then count the droplets wasted then stop until a new kit is fitted. Fitting a new kit means taking the covers off and lifting the printer innards out - and that needs some technical ability. Printer manufacturer policy is that you must take the printer to an authorised service center; which sounds fine until you find out its 300 miles away and charges two-thirds the price of a new printer for the job.

Carriage Faults

Printheads aren't the only possible cause of faults like streaky print, although they are the most likely. Streaky print could conceivably be caused by bad contacts in the carriage or the main logic, or by metal-fatigued conductors in the carriage cable. Some nozzles may not be receiving the print commands regularly or at all. Whether this type of fault can occur with the MP640 we don't know but it certainly can with other inkjet printers. (We don't have a circuit diagram)

Logic Faults

Logic boards scarcely ever go wrong. Most faults that people think are the logic are failures to set up Ethernet properly, driver mismatches, jammed or dirty sensors or cables not seated properly. Logic boards hardly ever go wrong (with a few exceptions). Quite truthfully, lightning strike is more likely.

Lightning strike will damage Ethernet or USB ports and possibly the power supply. Conceivably a printer will still work as a copier but won't communicate. However it is difficult to damage a recent Ethernet with a glancing blow (they are designed to cope) so unless lots of things go wrong at the same time it probably isn't that.

Test the printer itself by making a copy. If the printer can make a copy then any fault is not very likely to be the logic. Test Ethernet by getting its IP address and then pinging it.

If a logic board does fail the printer is essentially scrap. We will quote you for a replacement logic, but Canon's new spare price is usually unnatractive. What you want is a "pull" or transplant from a scrap printer that died because of blocked printheads or a damaged control panel.

Control Panel

One of the attractions of printers like the MP640 is the LCD display which makes copying and photo printing quite easy with or without a computer. It helps with things like setting up the network as well. The LCD itself is not very likely to be a problem; the keyboard and jog-wheel control could be. A common issue with keyboards and control panels is drink spills; grit and sand can cause sticky keys as well.

If you spill anything into a keyboard (of any kind) turn the machine off immediately. Apart from the electrocution danger voltages that should drive one thing get shorted into another and destroy the chips. Most electical equipment will survive water if it is turned off at the time. Sugar deposits and tarnish may need cleaning out.

LCD touch-panels are replacing an LCD with keys on most gadgets so this is one point on which recent printers may be rather more attractive.

Platen Unit

The platen section of a printer holds the paper flat under the printhead and controls vertical motion. Within the practical life of one of these printers it isn't likely to go wrong, although it might get contaminated with ink and need cleaning. Vertical position is controlled by two opto-encoder disks, one positions the paper from the paper feed mechanisms, the other ensures it ejects.

Sheet Unit

Paper feed is done by a soft rubber roller that engages the paper and pushes it into the platen. If this was an office quality laser-printer the roller and separation pad would be replaceable - but they aren't. The roller only seems to be available as part of the ASF Unit.

Similar printers include the:

• MP540, MP550, MP560
• MP630, MP640
• iP3600, iP4600, iP4700