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  1. #1
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    HP Designjet T790 Faulty ink cartridge message

    Hi:

    New member here. Having problem with printer constantly saying yellow cartridge is faulty.

    Bought this printer from a college that was getting rid of it. It's so clean inside and out, I wonder how much it was used. Haven't been able to access the reports yet but will be curious to see how much use it's had.

    When I got it, all the ink cartridges were empty. But the level indicator on the screen would alternate between empty and 100% full. And the expiration date would sometimes say 12-31-1969. So I replaced them all. But now have an error on the yellow cartridge that I can't seem to beat.

    Replaced the yellow cartridge because the other was empty. So I replaced with new (but expired) yellow cartridge OEM. It accepted it fine. Then it wanted a new cyan/magenta printhead. Replaced that. Then got error that printhead replacement not completed. So reseated printhead but kept getting same error. It finally completed (or so I thought) and then wanted a replacement MK/yellow printhead. Replaced that and then got error again saying both magenta/cyan AND the MK/yellow printhead replacement not complete. (Each time I insert the printhead, I let it sit for as long as it needs but keeps coming up w/the incomplete error.) Then, after the last time I tried reinserting the printheads, began getting the faulty yellow cartridge error. I've tried another cartridge but it's not OEM. I have another OEM (expired) cartridge coming and will try that next.

    Tried removing all ink and all printheads and rebooting but no change.

    Maybe air in the lines? Would that cause it to throw a faulty error?

    Any input much appreciated.

  2. #2
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    HP Designjet T790 Faulty ink cartridge message

    Kiran Otter's Avatar
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    Re: HP Designjet T790 Faulty ink cartridge message

    Make sure you update the firmware. I seem to recall there being an issue with it corrupting the date code on the ink cartridges and they'd show some impossible date like 1969 and say they're all faulty. But after a firmware update they were accepted.

    You could have air in the ink tubes. How long did the printer sit? You can get a syringe from LPS Computer and use it to draw the ink through the tubes to the carriage. About 10ml is plenty. If there's air you can usually hear it come through. And if there was air it will often ruin the associated printhead.

    I wouldn't trust a non-HP ink cartridge to know if it's truly faulty or if something is wrong with the printer.

    Kiran

  3. #3
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    Re: HP Designjet T790 Faulty ink cartridge message

    Thanks for the reply.

    Updated the firmware AFTER the cartridge started giving weird expiration date. Does the printer write to the cartridge or only read the chip? Once that date shows up, does that mean the cartridge is useless?

    All cartridges and printheads are HP OEM. Printheads are not expired but some of the new cartridges are. But they were sealed when I got them a couple weeks ago.

    Yes, next thing to try is the syringe. I have one I bought a couple years ago while working on my 5000 model. Works great.

    (Compared to this one, that 5000 is a cake walk to work on!)

    I'm not sure how long the printer has been sitting so not certain of the condition of the tubes. But the syringe should give me some answers. I'll probably draw all the colors, just to be sure. I can do that with the power off, correct?

    Again, thanks. I'll update the thread as I go.

    BTW, when the printer is booting up, the three lights on the formatter light up. The "l" lights up. The the "ll" lights up and the "l" starts to blink and continues to blink while "ll" and "lll" stay solid. After that, all three go out.
    Does that sound normal?

  4. #4
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    HP Designjet T790 Faulty ink cartridge message

    Kiran Otter's Avatar
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    Re: HP Designjet T790 Faulty ink cartridge message

    I would use the syringe with the power off, yes. Tell the printer you want to replace a printhead, and while the carriage is out from the service station, power the printer off. Make sure the ink cartridges have sufficient ink in them! When you're done, I would start the printer without the printheads inserted, and insert them once it's initialized.

    The printer does write to the chip on the cartridges; that's how it tracks how much ink is left. 'Expired' supplies just means HP won't take them back under warranty. They function just the same.

    I don't know about the 3 LEDs but that sounds normal. The manual only gives examples of error states. If it's initializing and functioning without an error on the front panel then it's OK.

    Kiran

  5. #5
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    Re: HP Designjet T790 Faulty ink cartridge message

    Thanks so much for the info! I'll give it a go, hopefully tonight, and post back results.

    This is my first attempt at fixing a T series so it's been a learning experience, to say the least.

  6. #6
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    HP Designjet T790 Faulty ink cartridge message

    Kiran Otter's Avatar
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    Re: HP Designjet T790 Faulty ink cartridge message

    My only 'word of wisdom' is to completely rule out any consumables before you start replacing parts. Having 3 yellow ink cartridges that all read faulty is sometimes just 3 faulty cartridges and nothing more. Try them in another printer to see if they work. Get a 4th cartridge. Also realize that another ink cartrirge/printhead can make its neighbor appear defective. Try the suspect cartridge/printhead by itself with the others removed. If it appears OK and then it's suddenly faulty when you insert another, that one you just inserted is likely causing the problem.

    Kiran

  7. #7
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    Re: HP Designjet T790 Faulty ink cartridge message

    Only other printer I can try the faulty cartidges on is one we have at my workplace. I can try it there as long as it doesn't mess up THAT printer. (My boss would not be happy if it did.)

  8. #8
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    Re: HP Designjet T790 Faulty ink cartridge message

    Update:
    I put in a new, unexpired yellow ink cartridge and it also read as "faulty". I had another yellow cartridge that had been used in a T1200 printer that was almost empty so I tried that one. It recognized the cartridge and displayed the "low ink" symbol but at least it's reading the cartridge. I tried reinstalling the previous cartridges again and they still read as "faulty". So that means I've tried 3 different yellow cartridges and two out of three have been "faulty". Hmmm. Also, while reseating the yellow cartridge and finally getting it to recognize, then the cyan, and magenta came up as being empty on the display and asking to be replaced. I reseated them a couple times and finally got them back to working. So now all six cartridges are reading. But I noticed the three that threw error codes or came up being empty or faulty are right next to each other. The other three have not had any problems and consistently read as "full" as they should.

    So to deepen the mystery, after the ink cartridges came back on line, the printer would allow me to let the printheads complete their install. So I went to the printhead section and selected "replace printheads", which I didn't actually remove the printheads, it just went into installation mode. Time on screen says it would take about 8 minutes. After that elapsed, it said to wait another 5 minutes. Okay, I expected a long time to complete the printhead install. (Up to an hour, according to the service manual when only replacing one or two printheads.) While waiting, I have my flashlight trained on the carriage and watching it move in and out of home position and watch the service station sled move back and forth with no problems.

    After the 5 minutes are up, I start hearing a very distinct and loud(ish) sound coming from the right side back from the printer. (I believe there's a circuit board back there, according to the service manual. But don't see anything about any relays located back there.) It sounds like a relay clicking. It is accompanied by another sound I can't describe. Very steady. Sort of a humming but like something is turning. And the clicking is rythmic. It follows a distinct pattern. It clicks about 5-6 times in a rythmic patter, then stops for about 15 seconds, then the pattern repeats.

    I watch the service station and other components to see if something it trying to move but being stopped and see nothing. Still sounds like a relay clicking. It does this for about another 2 minutes and then goes into the "possible paper jam" error. Only option then is to use the rear switch to reboot the printer. It then initializes and comes back to it's home screen and gives yellow exclamation points saying the yellow ink cartridge is almost empty and that the cyan/magenta and PK/yellow printheads have not completed the installation.
    While watching the carriage when parked over the sled, I can see whisps of smoke coming out, like the printheads are heating up and burning off excess ink maybe? The service station surfaces below the printheads look wet but that's pretty normal I think.

    After about 45 seconds of this, the printer throws up an 86:01 error code. Display says "Possible paper jam". No paper in the machine, and I can now grab the carriage and freely move it out of the home position, even with the power still on. That's unusual. Usually, you can't move the carriage when there's power present. Anyway, that's been my experience.

    So I reboot the printer and go through the entire process again. Same thing 86:01

    Set up to do it again but this time I load paper. Same results. Same clicking, same carriage movements, same error. So I unload the paper and reboot.

    This time, when rebooting, I get that generic 79:04. I reboot and then it comes back to the home screen after initializing.

    So I think it's time to remove the right hand cover and run it again and see what's clicking in there and see what's making the sounds I hear. Maybe this weekend. I've looked at the service manual and it's pretty complicated, compared to other printers I've worked on.

    I did do a restore on the hard drive from the front panel under "Service Utilities". Also restored to factory defaults and made sure the firmware is still showing the latest firmware update done a few days ago.

    So I'm getting the idea that the service station is not working correctly, causing erroneous codes to show up. Or the hard drive isn't working correctly, giving codes that aren't correct.

    I'm tempted to put in a new hard drive and see if that solves any of the mysterious things like the 12-31-69 dates I saw on the faulty yellow cartridges. Haven't tried the cartridges in another printer yet to see if they actually are faulty.

    As mentioned before, the inside of the printer looks like it just came out of the factory so I think this problem has been going on for some tiime and the previous owner didn't use it very much due to the errors, got fed up and sold it to me for next to nothing. But I'd sure like to pinpoint the problem.

    Thanks for reading. Would love to hear any insight or suggestions anyone may have.

  9. #9
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    HP Designjet T790 Faulty ink cartridge message

    Kiran Otter's Avatar
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    Re: HP Designjet T790 Faulty ink cartridge message

    Quote Originally Posted by D Hook View Post
    Update:
    I put in a new, unexpired yellow ink cartridge and it also read as "faulty". I had another yellow cartridge that had been used in a T1200 printer that was almost empty so I tried that one. It recognized the cartridge and displayed the "low ink" symbol but at least it's reading the cartridge. I tried reinstalling the previous cartridges again and they still read as "faulty". So that means I've tried 3 different yellow cartridges and two out of three have been "faulty". Hmmm. Also, while reseating the yellow cartridge and finally getting it to recognize, then the cyan, and magenta came up as being empty on the display and asking to be replaced. I reseated them a couple times and finally got them back to working. So now all six cartridges are reading. But I noticed the three that threw error codes or came up being empty or faulty are right next to each other. The other three have not had any problems and consistently read as "full" as they should.
    Like I said, one ink cartridge can cause its neighbor to appear faulty. Always try them by themselves with the other cartridges removed to test.

    Quote Originally Posted by D Hook View Post
    So to deepen the mystery, after the ink cartridges came back on line, the printer would allow me to let the printheads complete their install. So I went to the printhead section and selected "replace printheads", which I didn't actually remove the printheads, it just went into installation mode. Time on screen says it would take about 8 minutes. After that elapsed, it said to wait another 5 minutes. Okay, I expected a long time to complete the printhead install. (Up to an hour, according to the service manual when only replacing one or two printheads.) While waiting, I have my flashlight trained on the carriage and watching it move in and out of home position and watch the service station sled move back and forth with no problems.
    Yeah, it takes an eternity to 'prepare' the printheads. Meanwhile it's dumping a ton of ink into the service station.

    Quote Originally Posted by D Hook View Post
    After the 5 minutes are up, I start hearing a very distinct and loud(ish) sound coming from the right side back from the printer. (I believe there's a circuit board back there, according to the service manual. But don't see anything about any relays located back there.) It sounds like a relay clicking. It is accompanied by another sound I can't describe. Very steady. Sort of a humming but like something is turning. And the clicking is rythmic. It follows a distinct pattern. It clicks about 5-6 times in a rythmic patter, then stops for about 15 seconds, then the pattern repeats.

    I watch the service station and other components to see if something it trying to move but being stopped and see nothing. Still sounds like a relay clicking. It does this for about another 2 minutes and then goes into the "possible paper jam" error. Only option then is to use the rear switch to reboot the printer. It then initializes and comes back to it's home screen and gives yellow exclamation points saying the yellow ink cartridge is almost empty and that the cyan/magenta and PK/yellow printheads have not completed the installation.
    The clicking sound is the primer on the side of the service station. Usually when it gets stuck in this mode it's because of a printhead. Remove the printheads and start the printer, then go through the process of installing the printheads again.

    You probably just have a bad printhead. Sometimes the plastic that carries the electrical circuit down to the nozzles separates from around the nozzles and can cause interference with the service station. Looks like this:

    bad head.jpg

    If the printheads are all the originals, and this printer sat somewhere unused for a long time, I would just flat out replace all 3. Even if you do get past getting them initialized I would suspect there to be a lot of nozzles out due to them sitting.

    I wouldn't replace the hard drive. Nothing you've described suggests it's at fault. Make sure the contacts that mate with the ink cartridges are clean and not covered in ink. It sounds like the cyan or other cartridge is really the bad one but making the yellow misbehave. They're all connected through a matrix so as I said, one cartridge can cause another to appear faulty or do odd things.

    Kiran

  10. #10
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    HP Designjet T790 Faulty ink cartridge message

    Kiran Otter's Avatar
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    Re: HP Designjet T790 Faulty ink cartridge message

    Also, inspect the belt that draws the carriage back and forth. At this age, I would suspect it as starting to dry-rot. It should be shiny. If it looks flat and bits are coming off, it needs to be replaced. Usually they last 3-5 years, regardless of how much the printer is used.. at least here in South Florida.

    Kiran

    PS - I forgot, these use a heavier belt that lasts much longer. But still inspected it just the same.

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