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HP L7780 CIS -> General HP88 CIS discussion
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I used to have an Officejet 9110, one of those HP business inkjets with the built in ink pump which makes putting a CIS on these a breeze and you don't have to worry about ink levels as the ink flow is controlled by a pump and pressure sensors in the printer.

I now got an L7780 and due to the rumors that they added an anti refill system (which I've now been told is false) I decided to get a pre built CIS system for it for $55, it works well so far, but part of the ink pump and pressure sensor in these business printers is in the cartridges themselves, and these fake cartridges that came with the CIS don't have the pump part in them, meaning the printer can no longer control ink flow and pressure and I'm concerned this may cause problems or premature wear of the printheads, which are now themselves the inly "ink pump" left, they were not meant to pump ink like that, the printer's ink pump was, and is now non functional.

Do you think this could cause any problems? Should I attach it to original HP cartridges to restore the ink pump's function? It's a quite powerful pump also, when I had forgotten to put small air inlet holes, it actually squashed my ink bottles from the vaccum pressure.

For anyone who wants a CIS, and after reading the nightmares it can be to put on home printers, I really think if you want a CIS, these HP ink pump equipped business printers are by far the best option, and the fastest inkjets available today at 35 pages/minute.

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I wasn't aware of any "pump" in the actual cartridges themselves and so I grabbed an empty original OEM cart and pulled it apart.

In a nutshell there is no pump.. The ink is a silver foil bag with an outlet and if you pull the base off the cartridge you'll find hole plugged with a small plastic ball which is where ink is originally pumped into the cartridge. About the only other difference is a rubber bulb/bump at the base of the cartridge which could, I suppose be used as a sort of pump style device but to be honest I doubt very much if it's required in a CIS situation.

If anything I've discovered that these printers along with the K550, K5400 require a more positive ink pressure so what I have done is elevate my reservoir bottles so the ink level is slightly higher than the top of the cartridges. This seems to work quite well and should offset any pumping issues.


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Printers: (Canon) MP500/830, MX700, iP4000/4200/4300/4500/5200, iX4000(A3) (Epson) C84/86, D88, CX6600, R285/800/1900 (HP) K550, K850, K5400, L7680
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Having had a chance to think this through a little further and cogitate for a bit I realised that the "pump" you'd referred to was perhaps a little misleading.

On the base of the HP88 cartridges there's a rubber bulb which I hadn't really considered. It seems that this bulb gets prodded by some mechanism in the cartridge recepticle on the printer and helps increase pressure somewhat so that it flows into the printhead. In essence it's not so much a pump in the traditional sense as a sort of "hack" that HP have resorted to, to ensure there's sufficient pressure.. at a guess, especially when the ink levels are low.

Thinking about it logically it makes some sense but for anyone who's put together an extension using compatible cartridges that are tube fed from external reservoirs this "pump" mechanism will have no benefit at all. It does however indicate a possible reason for the problems with initial ink flow on the black (it doesn't seem to effect the other colours). You seem to get a sort of starvation banding for the first inch or so and then it kicks in to print normally.

The only solution I've come up with is to raise the ink reservoir levels so they are about an inch or so above the top of the cartridges and adjust as necessary.


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Printers: (Canon) MP500/830, MX700, iP4000/4200/4300/4500/5200, iX4000(A3) (Epson) C84/86, D88, CX6600, R285/800/1900 (HP) K550, K850, K5400, L7680
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Well the black buldge under the cartridges is essentially the "piston chamber" with the piston being on the printer itself. It is in fact an ink pump, you can hear the ink pump motor run during printing, it has a very distinctive sound different from any other motor in the printer (it's the weird sound you hear right after inserting cartridges and closing the cartridge door).

During printing, a piston constantly (or almost, it goes with the sound I described above) pumps against this rubber buldge, when it presses down on it, ink is pumped from the black buldge to the printheads, and when it releases ink is pumped from the cartridge to the black buldge, where it then presses against it again to send it to the printheads, it's a pump system with one way valves. This is also what detects when the cartridge is empty, if the black buldge no longer expands after being pressed, this indicates a vacuum, which itself indicates an empty cartridge.

As I said my cheap pre built CIS system disabled my L7780's ink pump so I no longer hear it run during printing.

Another fact confirming there is indeed an ink pump is that on my old Officejet 9110 whoch had the same cartridge system, I had once gotten an "Ink pump motor stalled" error.

About the black having problem at the start of the first page, this is normally due to air bubbles being trapped in the printhead, this happened to me but after several thousands prints it seems to have gotten the air out, otherwise the solution is to replace the affected printhead or live with the problem (living with this problem will dramatically accelerate the aging of the printheads).

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aab1 wrote:
Well the black buldge under the cartridges is essentially the "piston chamber" with the piston being on the printer itself. It is in fact an ink pump, you can hear the ink pump motor run during printing, it has a very distinctive sound different from any other motor in the printer (it's the weird sound you hear right after inserting cartridges and closing the cartridge door).

Yeah, that makes sense... I wouldn't see it as a pump so much though as a shunt or similar as it's simply enhancing the ink pressure rather than pumping it in the traditional sense.

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During printing, a piston constantly (or almost, it goes with the sound I described above) pumps against this rubber buldge, when it presses down on it, ink is pumped from the black buldge to the printheads, and when it releases ink is pumped from the cartridge to the black buldge, where it then presses against it again to send it to the printheads, it's a pump system with one way valves. This is also what detects when the cartridge is empty, if the black buldge no longer expands after being pressed, this indicates a vacuum, which itself indicates an empty cartridge.

I think where we disagree here is in the definition of "pump". The piston is not constantly increasing pressure forcing/feeding more and more ink to the head, it's simply a one shot pressure increase that ensures that low ink levels don't affect ink flow towards the end of the printers life.

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As I said my cheap pre built CIS system disabled my L7780's ink pump so I no longer hear it run during printing.

Well it doesn't disable it per-se it just doesn't provide a bulb for the piston to press against and regardless because your (and my) CIS system has a vent in the reservoir it negates any effect the piston would have anyway.

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Another fact confirming there is indeed an ink pump is that on my old Officejet 9110 whoch had the same cartridge system, I had once gotten an "Ink pump motor stalled" error.

Again, it's a definition or terminology thing... But if they call it a pump then I guess we can Smile...

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About the black having problem at the start of the first page, this is normally due to air bubbles being trapped in the printhead, this happened to me but after several thousands prints it seems to have gotten the air out, otherwise the solution is to replace the affected printhead or live with the problem (living with this problem will dramatically accelerate the aging of the printheads).

That's about what I figured and in truth I've never really found a successful technique to reducing this problem aside from adding additional pressure by elevating the reservoirs.


_________________
Printers: (Canon) MP500/830, MX700, iP4000/4200/4300/4500/5200, iX4000(A3) (Epson) C84/86, D88, CX6600, R285/800/1900 (HP) K550, K850, K5400, L7680
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Thanks for the reply.

I wanted to correct you on one thing though, you say it provides one shot pressure but that's not how it works, they way I figured it works is that each plastic "piston" that comes and press against the black buldge is spring loaded, this does that even though the printer motor pushes the pistons all the way, they will barely move at all and remain under the pressure of the spring. As the printer prints, the black buldge slowly "deflates" causing the piston to move in more and more under the pressure of the spring (against the pressure of the ink in the black buldge holding it back). Those pistons also have sensors, when it detects the piston has moved all the way out, it knows the black buldge is empty and will retract all pistons (allowing the black buldges to refill with ink) and then pushes them all back, applying a constant pressure to all 4 buldges, so there really is a constant pressure. If ever you have an old broken hp printer like these, you can try cutting one of the ink tubes going to the printheads and I'm sure the ink pump will start pumping constantly, as it only stops once the other side is also pressurized, so you'd hear the pistons move back and forth constantly while ink shoots out the tube.

You can test what I said like this:
Put all 3 colors cartridges in except for the black, put only the small plastic base of the cartridge which holds the memory chip so it detects a cartridge. Now if you closed the door like this you'd get a "Black ink cartridge empty" error as it would detect the buldge has collapsed (in this case it's actually missing, but this simulates an empty cartridge which causes the buldge to collapse under the vacuum pressure). Now open the door and put your finger against the piston and then insert something into the cartridge door sensor so it thinks you closed it. If you resist the pressure of the piston it should let go, but if you slowly allow the piston to move out, it will then retrack and extend again, if you leave it come out several times it will eventually give up on trying to pump ink and declare the cartridge empty.

I've had HP printers with this ink pump system for many years now so I now a lot about them, the L7780 is at least my 4th printer which these HP ink pumps, I think it's an awesome system.

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About the black having problem at the start of the first page, this is normally due to air bubbles being trapped in the printhead, this happened to me but after several thousands prints it seems to have gotten the air out, otherwise the solution is to replace the affected printhead or live with the problem (living with this problem will dramatically accelerate the aging of the printheads).

That's about what I figured and in truth I've never really found a successful technique to reducing this problem aside from adding additional pressure by elevating the reservoirs.


Actually the blank ink problem is having to do with that most places sells this Ciss with dye black ink while the ink should be pigment.

It does not happen at all when you run it with correct kind of ink.

At least that is been my experience.

I could not get good black print until this was discovered and changed to pigment black.

/Amin

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Color_Workshop wrote:
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About the black having problem at the start of the first page, this is normally due to air bubbles being trapped in the printhead, this happened to me but after several thousands prints it seems to have gotten the air out, otherwise the solution is to replace the affected printhead or live with the problem (living with this problem will dramatically accelerate the aging of the printheads).

That's about what I figured and in truth I've never really found a successful technique to reducing this problem aside from adding additional pressure by elevating the reservoirs.


Actually the blank ink problem is having to do with that most places sells this Ciss with dye black ink while the ink should be pigment.

It does not happen at all when you run it with correct kind of ink.

At least that is been my experience.

I could not get good black print until this was discovered and changed to pigment black.

/Amin


This is also true, my CIS system had dye black ink and I had this issue, I replaced the in and made several photocopies with the scanner lid open to print whole black pages to pump that junk out of the system, it's now running normally.

By the way, I noticed the original HP ink gives me dark pitch black, but even my pigment ink refill isn't as black, have you found a pigment black refill ink that's as black as HP's? Most people would probably swear the original HP black is laser toner since it's such a deep, pitch black.

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This is also true, my CIS system had dye black ink and I had this issue, I replaced the in and made several photocopies with the scanner lid open to print whole black pages to pump that junk out of the system, it's now running normally.

By the way, I noticed the original HP ink gives me dark pitch black, but even my pigment ink refill isn't as black, have you found a pigment black refill ink that's as black as HP's? Most people would probably swear the original HP black is laser toner since it's such a deep, pitch black.



Hi

Actually, it will sound like self promotion when I answer this question of yours but I will first explain who I am:

I am co owner of a company named Color Workshop, we are based in Sweden.
We sell ciss that we import from China and then quality control them.
After this we fill the ciss with ink from an American factory or Nazdar/Lyson ink. Nazdar is an American company that offers Screen inks and they have since January or February of 2006 bought up the British company Lyson and now offer theres ink as theirs digital line of ink.
We have just started with Lyson ink and products so we have not had time to update our page yet with all the information.

But the pigment black ink that we offer for this HP printers comes from the American factory and it is as black as any Laser printers print on plain paper.

So to answer your question, yes I believe we offer ink that is as black as HPs original pigment black.

our web page is in Swedish, but I am not sure if I am allowed to type the web address here so if you are interested or have any questions don't hesitate to send a PM to me.

Best regards,
Amin

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aab1 wrote:
I wanted to correct you on one thing though, you say it provides one shot pressure but that's not how it works, they way I figured it works is that each plastic "piston" that comes and press against the black buldge is spring loaded, this does that even though the printer motor pushes the pistons all the way, they will barely move at all and remain under the pressure of the spring. As the printer prints, the black buldge slowly "deflates" causing the piston to move in more and more under the pressure of the spring (against the pressure of the ink in the black buldge holding it back). Those pistons also have sensors, when it detects the piston has moved all the way out, it knows the black buldge is empty and will retract all pistons (allowing the black buldges to refill with ink) and then pushes them all back, applying a constant pressure to all 4 buldges, so there really is a constant pressure. If ever you have an old broken hp printer like these, you can try cutting one of the ink tubes going to the printheads and I'm sure the ink pump will start pumping constantly, as it only stops once the other side is also pressurized, so you'd hear the pistons move back and forth constantly while ink shoots out the tube.


Ah... I see... Ok... well I stand corrected then.. I had assumed (stupid of me) that the bulge part allowed free flow back and forth into the silver bag reservoir part of the cartridge but from what you seem to be saying there's actually a one way valve in there that allows ink to feed in to the bulb but not back into reservoir part. If that's true then it makes sense that the system you've mentioned does indeed provide a constant pressure and I'm seriously wondering why the CIS cartridges haven't mirrored this (probably too difficult or cost prohibitive).

Thanks for the explanation though and being patient with my "You're wrong" Smile


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Printers: (Canon) MP500/830, MX700, iP4000/4200/4300/4500/5200, iX4000(A3) (Epson) C84/86, D88, CX6600, R285/800/1900 (HP) K550, K850, K5400, L7680
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