An Illusory Intertwingling of Reason and Response

Tech: Yes, I’m a geek. I admit it. At least I’m not a nerd!

Tafel :: tech

Tuesday, July 12, 2005

Fun with the Canon IR8500 in Service Mode

Revised 11/09/2005 09:45:30

The Canon ImageRunner 8500 (from here on out called the Canon IR8500) is a simple joy of a machine to run. It rarely jams, hardly ever malfunctions, and even when it does, the service techs are actually enjoyable to work with (which is more than I can say for some other vendors, such as R*COH, eh?). However, there’s only so much legitimate fun to be had from any machine. To really get the full enjoyment of the IR8500 (it being no different from any other machine in this respect), you have to get under the hood. Of course, Canon doesn’t want you to do this, for entirely-understandable liability reasons: in fact, service techs can lose their jobs for giving out the code to put the machine into service mode. (For the record, the code can be found online, so there’s no reason to go shooting my service tech, okay Canon?)

First, you have to go into service mode. I mean, come on, this is where all the fun is, right? Service mode in the Canon IR8500 is entered by pressing the “*” (Additional Functions) button, then immediately pressing “2” and “8” together, followed by the “*” again. This is known affectionately as the “star-twenty-eight-star” among Canon service techs.

If you’re not greeted by a beautiful white screen with a few boring grey buttons on it, try again . . . and again . . . and again if necessary. It’s a skill which takes a while to get the hang of, and even then, experienced service techs sometimes have to do it several times before it finally “takes.” (To exit service mode, press “Reset” several times until the machine returns to normal, end-user menus.)

Before you go pushing any service-mode buttons on your dear old IR8500, let me give you a friendly little WARNING: by entering service mode, you automatically incur the disfavour of the entire multinational Canon corporation, your friendly neighborhood service tech, and your boss (if you mess anything up). That said, let’s dig in.

Viewing the Analog Sensor Data (temperature, etc.)

Menu: COPIER > Display > ANALOG
Just hit the “Copier” button (the top one) upon entering service mode. The first panel/tab it drops you in ought to be the “Display” tab. From there, hit the “Analog” option. There’s not much to do here, but it’s actually where I spend most of my service-mode time. When the copier’s warming up, there’s not a whole lot to do; so you might as well watch the fuser temperature rise, right? Here are your readouts: pick your pleasure:

  1. TEMP (ambient temperature, °C)
  2. HUM (ambient relative humidity, %)
  3. ABS-HUM (ambient absolute humidity, g/m3)
  4. OPTICS (optics temperature, °C)
  5. FIX-C (fixer center temperature, °C)
  6. FIX-E (fixer end temperature, °C)

The ambient temperature (TEMP), is, of course, the temperature of the room around you, as measured from somewhere in the copier itself (and as such, it has a tendancy to be a tad high: for example, it usually gives me a reading of 23°C on a 21°C day). The optics temperature (OPTICS) is measured in the optical chassis, in the top of the machine. They are kept heated, mostly to preclude condensation, to around 75°C. The higher the relative humidity, the higher this temperature should be, I assume.

The relative humidity (HUM) is the most reliable measurement of humidity (and of course, will be a tad low, since the temperature it is measured with is a tad high), since it is independent of pressure and temperature effects on air volume.1. The absolute humidity (ABS-HUM) gives you the current mass of water per cubic meter of air, and as such, is affected by barometric pressure (because barometric pressure affects the volume of a given mass of air or other gas).

The fixer temperatures (FIX-C and FIX-E) are the temperatures of the center and ends of the top fixer (or, fuser) roller. I had originally thought that they were top versus bottom rollers (FIX-E is usually about 10°C cooler than FIX-C — ~187 as opposed to ~197°C — os I figured that that FIX-C was the bottom roller, the extra heat compensating for its indirect contact with the toner, since only the top roller directly contacts the unfixed/unfused toner), but a friendly Belgian Canon engineer read this post and corrected me.

It’s mildly amusing to watch the fixer/fuser temperature rise as the copier warms up, but other than that, there’s not a whole lot of action here. Now if you want to actually feel like you’re doing something . . .

Cleaning the Corona Wires

Now, in recent versions of the IR8500 copy machine firmware, Canon has provided a user option to clean the corona wires. However, this procedure is probably a pale and insipid version of the actual cleaningr process, since they don’t want ordinary people doing anything which could potentially harm the machine. Reasonable. Do I let that stop me? No. Here’s how an honest-to-goodness Canon service technician gets the black lines out of your copies. (Yup. If you have streaked copies and you’ve already wiped off the fuser/fixer rollers, but to no avail, this may do the trick without a visit from your Canon Man.)

This will take a few minutes, but it’s almost guaranteed to get rid of streaks and lines in your copies if they were even remotely caused by dirty corona wires.

See, the corona wires have to provide an even electrical charge (static electricity) to the sheet of paper so that it picks up toner powder evenly. If there is something on the corona wire causing a stronger charge at one point, that may result in a line across the paper where the sheet passes across that part of the corona (electrical field). See How Stuff Works for a detailed explanation of how the xerographic process (the process used in photocopiers and laser printers) works.

Viewing the Maintenance Counters

Menu: COPIER > Counter
The ImageRunner 8500 keeps track of the wear and tear of nearly every replaceable part. A counter is incremented for every copy (or, “click”) in which a given part is involved. For some items, such as the cleaning web, this means that the counter is incremented with every copy. Other parts, such as paper takeup rollers, are used only intermittently (i.e. only one paper storage drawer is drawn from per copy), and therefore have counts far lower. Counters are reset when a part is replace (ideally, though I have some parts which show a 1,000% overuse simply because their counters have never or rarely been reset when they’ve been replaced.

Oh, and that’s the other cool thing about the counters. They give you the percentage lifespan used for each counted part. Has your tech been doing his job? Now you know.

Other Miscellaneous Schtuff

  • Errors and Jams: these items give you the time an error code was set and the time it was cleared, along with the code itself and the size of paper involved (third, fourth, sixth, and ninth columns, respectively).
  • Function > MISC-P > P-PRINT: a seven-page printout of your current machine parameters and software package versions, along with your maintenance counter readings: the “Copy Service Report”
  • A whole lot of other things. Just don’t break anything, okay?

Hope you’ve enjoyed this little exposition (or, expoundification, perhaps?). Remember, I am in no way liable for any damage you may do, which may result in your service tech laughing at you and charging you double. If you want someone to blame, you can find the service code online sometimes. Anyway, I didn’t make you do anything, eh? (But speaking of making you do stuff, there’s some more service-mode tips and tricks for the ImageRunner series at the Imaging Systems Group “Canon Black and White Products” pages.

Humidity is the amount of water saturated in air (or another gas). Absolute humidity gives the mass of water vapor per unit volume of air in the atmosphere, while relative humidity is the ratio of the partial pressure of water which is actually present to the vapor pressure of water at that temperature, expressed in percent.

Wolfram Research, “Humidity”

Absolute humidity is the mass of water vapor per unit volume of air in the atmosphere. The mass of water at any given temperature is limited by the vapor pressure, which can be found in tables of water properties. A more useful notion is that of relative humidity.

Wolfram Research, “Absolute Humidity”

According to Dalton’s law, the pressure of a gas mixture is equal to the sum of the partial pressures of the gases of which it is composed. In the atmosphere, water vapor always contributes a partial pressure to the total pressure, usually expressed in terms millimeters of mercury (or inches of mercury). At any given temperature the partial pressure of water can never exceed the vapor pressure for that temperature, otherwise it would condense into liquid water.

The relative humidity is the ratio of the partial pressure of water which is actually present to the vapor pressure of water at that temperature, expressed in percent. For example, if the local atmosphere has a partial pressure from water vapor of 5 mm of mercury and the temperature is 20°C, the relative humidity would be [R.H. = (5/17.5) x 

100% = 28.6%] image copyright Wolfram Research (since the vapor pressure of water at 20°C is 17.5 mmHg).

Wolfram Research, “Relative Humidity”

How Stuff Works
What if you had to resort to making carbon copies of important documents, as many people did before copiers came along? Or worse, imagine how tedious it would be if you had to recopy everything by hand! Most of us don't think about what's going on inside a copier while we wait for copies to shoot neatly out into the paper tray, but it's pretty amazing to think that, in mere seconds, you can produce an exact replica of what's on a sheet of paper! In this article, we will explore what happens after you press "Start" on a photocopier.

More at How Stuff Works, “How Photocopiers Work”