Canon iPF760 plotter - poor print quality (brand new printhead)

[Elmojo]

So as a follow-up to my previous inquiry about this machine, I have it mostly up and running, but I'm still struggling with a baffling print quality issue.
I've replaced the printhead with a new genuine Canon OEM one. I also installed a new maintenance cartridge.
When I run the nozzle check, it mostly looks good, except the black blocks are still missing a few little spots here and there and (really oddly) the upper right yellow block is missing completely.
I mean, it seems like there should be 2 of each color, but there's only one yellow grid.
How is this possible? When you replace the printhead, doesn't that replace all the nozzles?
When I print full color plots, I notice banding, so there's definitely something still not right.
I also occasionally get a hardware error 03800500-2F42, which I've looked up, and appears to point to a printhead.... okay...
I'm lost here...

The attached image shows the banding issue.
20230124_141801 (Medium).jpg

[blackcat4866]

That's an excellent sample to demonstrate.

I'm going to assume that those voids are occurring crossfeed. I believe that you've got a drive issue with the registration roller. There's a pulse wheel that monitors the rotation and speed. Sometimes that pulse wheel will become dirty, dusty, or it might scrape against the photointerruper, damaging the silk-screened black marks.

If those voids are in the feed direction, I would look at the carriage drive belt and pulleys. As the timing belt wears, it will pack the brass timing pulley on the motor with rubber shaving from the belt. With each rotation of the motor, you'll see the carriage hesitate.

=^..^=

[Elmojo]

Yes, I'm fairly certain the bands are in the direction of carriage travel. I'll definitely take your remarks into consideration for things to check the next time I'm on site. The machine is now installed at my main office, an hour away from where I work day-to-day. For some reason, I never thought to print a solid color test of that sort before putting it in place, and all the little tests I ran here looked okay.

Any thoughts on why I'm getting printhead errors and issues with the nozzle check, when the printhead is brand new? My (very limited) understanding of how these Canons work is that the printhead is pretty much the self-contained print engine, in terms of ink delivery at least. The ink tanks are just that, ink storage.
The service manual isn't all that helpful in regards to troubleshooting that error. It just says it could be most anything from a faulty main PCB to a bad printhead, with the printhead being the most likely. I'm certainly hoping it's not a main PCB or anything that serious, but I have no way of testing it, that I know of.

[blackcat4866]

There are a lot of possibilities what might cause loss of pixels:

If the purge unit is not cleaning the printhead surface properly, it can clog quickly. You can tell by looking at the purge unit. If it's not suctioning off the printhead properly, it will be a solid cake of dry ink.

It's possible that the ink is not being pumped to the printhead. You'll see air bubbles in the tubes. Often the cause of this is aftermarket ink cartridges. Counterfitters have become very good at copying the labels, but only genuine Canon cartridges have the word "CANON" embossed into the plastic case. If you have any counterfit cartridges, replace them with genuine Canon cartridges.

It's possible that the ribbon cable is damaged, that makes the electrical connections to the carriage. It's difficult to diagnose, since the ribbon must flex during normal operation, and it's not so easy to simulate those conditions in testing.

It's possible that the printhead is making a poor connection to the carriage PWB or the carriage PWB is faulty. You can clean the contacts with alcohol or contact cleaner. I had to laugh while watching another tech clean the contacts with contact cleaner, then wipe the surface with his fingers. OOPS! Lol!

It's possible that the head management sensor is malfunctioning.

It's possible that the main controller is bad.

Soooo ... how far down this rabbit hole will you go? My suggestion is to clean and examine the things that you can do for free (or as labor only), then consider parts. =^..^=

[Elmojo]

Thanks for the advice. A rabbit hole indeed! I'll have to see if they want me to come back down to try troubleshooting. I'm fairly sure the cartridges are genuine. At least the one I installed is, and the previous owner was a stat agency, so I feel like they would be required to use genuine consumables, but maybe not.
As you say, some of those things I may not be able to diagnose myself, especially since I don't know much about Canon machines, and all I have is the factory service manual. Honestly, it doesn't seem all that great. I'm used to Oce' and older HP manuals, which had TONS of step by step information for diagnosing issues. This one doesn't seem to have much. It pretty much says "got this problem? Replace this part".

[blackcat4866]

Yeah, the Canon manuals don't give you step-by-step anything. The error code information and service mode details, are about the only useful things. They just expect you to start throwing parts at the machine. =^..^=

[onlyinnewfoundland]

Try printing the nozzle check pattern in your test print menu at the machine...

See if you get a good looking Y M C block on the top and you should have 3 black blocks on the bottom.

Sometimes when the purge unit is failing, you will see the colors start to change because they are getting sucked back into the printhead or pooling instead of being drawn down into the maintenance box.

I just recently looked at an iPF750 for a customer and it has no yellow in the yellow tube, ink tank full. There are some matte black droplets in the line. So there is either an air leak, or the purge system is not capping the head properly.

Unfortunately, sometimes it will kill the head.

[Elmojo]

Try printing the nozzle check pattern in your test print menu at the machine...

See if you get a good looking Y M C block on the top and you should have 3 black blocks on the bottom.

From the OP: When I run the nozzle check, it mostly looks good, except the black blocks are still missing a few little spots here and there and (really oddly) the upper right yellow block is missing completely.

Does that mean anything to you? I'm not sure how one whole block of yellow can be totally missing. It's like that part of the printhead just isn't receiving a signal, even from the internal test print.
I assume there's supposed to be 2 blocks of each color, I haven't seen what a "correct" nozzle check looks like.

[blackcat4866]

Sometimes Cleaning A or Cleaning B will help. Keep in mind that while you're doing this, 3-4 cleanings will empty the ink cartridges and fill the maintenance container. It's surprisingly easy to consume hundreds of dollars of supplies. If the image quality is adequate and the enduser is doing enough print volume (the higher the better with ink based devices), these sort of printhead blockages can resolve themselves, in time.
=^..^=

[Elmojo]

Sometimes Cleaning A or Cleaning B will help. Keep in mind that while you're doing this, 3-4 cleanings will empty the ink cartridges and fill the maintenance container. It's surprisingly easy to consume hundreds of dollars of supplies.

That's exactly why I haven't done any more cleanings. I ran 2 cleaning As and one Cleaning B earlier, as part of my troubleshooting before I replaced the printhead. That killed the maintenance cartridge.
I then replaced the printhead and main. cart, and did a cleaning A after I still had the issue. That killed off my yellow ink tank, and dropped the maint. cart. to 80%. That's just nuts.
What's baffling me about this whole thing is that the printhead is new. To me, that says the problem has to be elsewhere, no? This is of course assuming that the new printhead isn't faulty, but I can't go chasing edge cases like that, or I'll lose my mind. lol
I think that purge unit (whatever that is), sounds suspect, but I don't know how to check it. I need to look that up in the Svc manual I guess.