QY6-0067 diagnosis

[PeterBJ]

I think a defective logic board is not supposed to be repaired but to be replaced. Just like there are no spare parts available for a purge unit or a scanner unit. The name unit says it all, they are replaced as complete units, not repaired. But of course a home user amateur service technician might sometimes have luck.

I think the cost of having a printer repaired after the warranty has expired is higher than the cost of a new printer, to make you buy a new printer which is more refill unfriendly. So it seems you can either discard the defective printer or try do repair it yourself.

 

[sneezer2]

@The Hat
Well, I guess there's a lot I'm not taking into account since there's a lot I don't know about. I guess that there are a lot of software issues and that you are referring to just one.
I welcome anything that would clarify any of these issues but I don't really get what you say. For example, I've never seen a fatal error but I take it that you mean I am cruising
for one and when it arrives, I will not be able to recover from it. That's OK, I'm sure you know a great deal more than I do.

It's true; I have not considered any signals "coming from the print head" but what are they? Well, temperature is a given and we all know that but are there others? And how
might they go wrong? I gather, but please correct me if this is not right, that, for instance, there would be an acceptable range for temperature permanently registered in
the EPROM and if a signal coming back is outside that range, then a fatal error would be generated and saved (probably in the EPROM). And that once that happens, the
logic board will no longer recognize or operate with that particular print head.

But when you say printheads "very seldom come back from a fatal error", do you mean this error is also recorded somewhere in the printhead? And that it will no longer work with
any logic board? Well, I suppose I would deserve that if it happened but so far I don't see how I "mess with it too long". Until now I have not done anything to either the printhead
or logic board except wash it out and put it back, as I believe I have made clear. Except try to think about these issues, including software.

Anyway, there is an issue with this particular printhead, which has been elucidated by @InkStainedFingers, who pointed out that 1/4 of the pigment black nozzles are not being
addressed. That was new to me and I took a bit of time to get onboard with it. However, I'm convinced now that it is accurate. That brings up several questions:
1) Exactly what fault, out of at least several possibilities, would cause this?
2) Why has that fault not caused a fatal error?
3) All I have done since soaking the printhead is use it for a couple of minutes to make a new nozzle check to verify that the first one is accurate. Since then the printer is
turned off. If I tried to keep using it, would that generate a fatal error? If I changed the settings to use dye black, as you have suggested, and then continued using the
printer, would that generate a fatal error? Why or why not? (This question is posed rhetorically.) At least so far, failure to address a block of nozzles doesn't seem to have
sent any signals back.
4) What could I possibly do among the things I have written about to cause a fatal error, other than (speculatively) continue to use the printer until this fault generates a
fatal error or else causes another fault that would do that? There is nothing but this that I can think I would do, which would have any effect on conditions inside the
printhead. If you know of any please let me know. If the printhead is otherwise faulty or becomes faulty, then I guess it could go fatal but that's just the risk I take,
either by messing with it or just by continuing to print. And that risk seems to exist with any printer at any time.

Finally, here is a speculation that I guess you may not like but I will put it forward anyway just for the purpose of thinking about things:
I've seen repeated warnings about defective printheads destroying the logic board and vice versa. No quibble there but among the posts that I have seen, I haven't found any
that actually specifies what that means. It appears (at least to me) that we are talking about two things. A logic board could presumably be "destroyed" by a fault that would
burn out some part, say +24V coming back from an internal short in the printhead to damage a driver chip somewhere. Or it could be "destroyed" by a fatal error. Why do
we have to consider that as a destruction. EPROMs can be rewritten unless they are physically damaged. There is even a procedure in some service manuals detailing how to
partially do this. Isn't it possible that someone could figure out how to address all the cells in this logic board EPROM and thereby restore the whole thing to factory condition
by overwriting any fatal error. I agree this would be a big job but considering what some people do already, I don't see why it would be impossible. If we can reset cartridge
chips, why can't we "reset" the EPROM.

Just rambling.

 

[sneezer2]

@PeterBJ
Yes, I think both your points are well taken. I agree.
But then why should we all be willing to put up with it.
After all, we are all human beings and some of us (myself excluded)
are smarter than most Canon engineers and a lot brighter than
anyone in their legal or marketing departments.

By the way,have you heard about the movement here in the US
for "right to repair" legislation.

 

[Ink stained Fingers]

If we can reset cartridge
chips, why can't we "reset" the EPROM.

I'm not getting your points really - if a printhead fails with a hardware failure - chip, short - whatever - how could an EEprom reset fix that problem ?
Bubble/thermal inkjet printheads wear out - the nozzle resistors with their frequent heating cycles , the coating of the metal films , with the hot solvent of the ink all can only stand a particular (high) number of ink shots, such a printhead is a consumables item, and HP offfers replacement printheads openly together with their inks in their shop for the office type printers, and nobody is complaining. Canon a kind of diffuses the issue and let the user think that it is a 'permanent' printhead. This goes back 30 or so years to the times HP was offering their deskjet printers with the prinhead on the cartridge, nobody cared that those printheads had a pretty limited usage time, and then Canon separated the printhead from the cartridges and advertised that as a 'permanent' printhead. And Epson soon went a step further to make the printhead even more permanent/long lasting - for the expected lifetime of the printer.
There is nevertheless one other difference between Canon and HP, HP typically has an error message on the display for a defect printhead, and a defect printhead does not kill the rest of the electronics.

 

[The Hat]

I welcome anything that would clarify any of these issues but I don't really get what you say. For example, I've never seen a fatal error but I take it that you mean I am cruising
for one and when it arrives, I will not be able to recover from it. That's OK

We don’t know whether prolong use of a print head with defective black nozzles will eventually kill the logic board or the rest of the print head, because we don’t actually know anything for sure, it’s all pure speculation on our part, but we still warn of the possibility.

I have never had a logic board go bang on me yet, but I’ve had plenty of heads go bang for no apparent reason, (No nozzles missing) I also have reset the logic board EPROM chip by installing a new print head for a couple of minutes and then reusing a head that was declared non-functional earlier, so it is possible.

Logic boards on Canon printers can be repaired and at great cost, but the print head is the only exception, once it burns out the nozzles as in your current print head (Black) then you must seek a replacement, new or second hand.

You can get used print heads from China, some of them work but most don’t, it’s based on the same logic that if a print head is declared software defective, then it may work in another printer, and sometimes they do.

You can indulge yourself with the internal working of your printer, and I will always encourage you to do so, but it still won’t stop me pointing out the pit falls when something goes wrong, because I don’t want you to lose a good printer...

 

[turbguy]

The missing nozzles on the Pigment Black are probably not "burned-out". I would expect that would be revealed as random lines missing from the grid on a true nozzle test print. As I've said before, one failed conductor or semiconductor on the nozzle die is probably all it takes to wipe out the operability of a bank of nozzles. That seems to show up as a regularly-patterned error in the grid, very frequently!

As far as I know, the only signals SENT BACK from the nozzle die to the main board are bulk temperature, not PEAK temperature. When overheat is detected, a cool down period (printing is paused) is initiated. Another signal is head EPROM info, that can identify the print head to the main board. Other signals from the Carrier (not the die) include ink level monitoring, and cart chip reading info. These signals are also carried by the ribbon cables from the print head carrier to the stationary electronics.

I suspect a localized overheat condition within the die occurs that bulk temperature monitoring cannot promptly detect,which is root cause for such failures. So, print slower (quite mode) and increase the drying time setting between pages (if printing multiple pages).

Until there is an actual circuit diagram of a Canon Print Head die released or discovered, we will never know the "innermost workings" of the "magic" going on within that die.

 

[sneezer2]

@inkStainedFingers
"if a printhead fails with a hardware failure - chip, short - whatever - how could an EEprom reset fix that problem ?"

Well, no, I wouldn't think so either. But if a "reset" or rewrite of the EPROM could recover a logic board that is not physically damaged,
that could be worth something.
On the other hand, "fatal error" still seems poorly defined. @TheHat (above) seems to have "recovered" a logic board by putting in a
new printhead. Presumably, he means that it was "fatal errored" although he doesn't explicitly say so. To some extent, that already
redefines the idea. I would very much like to see this sequence better understood so that we could evaluate conditions more readily
and undertake replacements with a little more confidence.

 

[sneezer2]

@TheHat
I appreciate the last couple of lines in your post. Please keep pointing out the pitfalls.
And I agree that this is all pure speculation but it has helped me to see some of the issues
that I didn't find obvious before.
Yes, I've seen ads for the Chinese heads but wouldn't buy it. Also have seen ads for
something they characterize as "new" printheads, evidently made in China.
Thanks again for your help.

 

[sneezer2]

@turbguy
Thanks. This is meat! I agree that we will never know the innermost workings but the
speculation here could possibly reveal a couple of general principles, such as the "spreading
out" of the data flow from a few ribbon cable conductors to thousands of individual
nozzles. This, I think is what tells us that the "regular pattern" in the nozzle check
shows most likely some kind of chip failure prior to the nozzles.
This should mean that those nozzles can't overheat because they are no longer even
addressed.
But what other conditions can cause a fatal error? So far, all I see is temperature
and printhead ID and even that can apparently be corrected or "reset" by putting
in a new head, if you've got the balls to do it! Maybe a short circuit inside the
printhead die or whatever other chip is in there. I don't see any signal coming off
the carrier as potentially inducing fatality.

At this point, if "forced" I would probably go ahead and do that. Maybe take off
the right cover and look to see if anything is burned. Possibly get a voltmeter on
the pads leading to the ribbon cables to verify there is no short.

 

[Technician]

Interesting thread this. If you go into Google/Images and copy & paste " Circuit diagram of a Canon print head die " you'll be rewarded with many images & schematics of said item. Whether that gets you any closer to finding out what's wrong with it is another thing, but still plenty to read about.