Disassembly of printhead HP11 (C4810A)

[giuseppe]

Since searching for "HP11 disassembled" did not turn anything up for me, I thought I'd upload a photo somewhere. This forum has proven to be a treasure already, so here is my two cents.

For disassembly you just unclip the top side four times. It is a very easy and reversable process. You don't need to take off the chip or flex band like I did (out of curiousity).

If you want to find out more, the relevant patent should be EP0875385B1. It does not mention though, what the plastic bag between the gray clamps should do that is attached to the top. I guess it is for applying not too high pressure on the ink (or the binder in our case), since it is connected to the outside atmosphere through a vent opening.

This started because I wanted to know, why our ProJet 460 complained that its printhead is too hot (1006: Head Temp Too High). We have just replaced it, but I am still curious to know how things work.

• What does the temperature sensor look like?
• Where should it be located?
• Where would you find more background on the history of this printhead? I know that HP hosts their HP Journal and I would have to go through all the numbers. Is there anything else or can you give some pointers?

[dragonator]

Hello and welcome,

Nice to see an opened HP11. I have the data ready to try the printhead myself, but I have found myself too busy to do anything with it. Can you see how the ink enters the printhead? I have seen the needle, but have a hard time figuring out where I need to insert the ink for this printhead if I made something myself.

Do the grey clamps spring inwards, compressing the bag? Printheads need to be kept at a slight vacuum, else the ink will run out. If the springs clamp the bag, this is a way to keep the printhead at a vacuum even when some ink is pumped in.

The temperature sensor should be right next to the nozzles on the circuit. The way to make these printheads is pretty close to semiconductor manufacturing (the resistors and driving components are on a wafer that also includes the nozzles) and so adding a resistor to this should not be difficult. I do not know how to fix or replace this. The quickest fix I think would be to make the printer just believe the printhead is still working, but I do not currently know if there is an analog pad that gives this value, or if there is an ADC in the printhead.

[KestrelS2B]

Thanks for the little tutorial! I was stuck with my own HP11, I'm embarking on a big project at work, an in-depth, book-sized report about this Cyprus investor visa in 2020, and I was worried it'd take all of my free time, and that I wouldn't be able to fix the heating issue on mine before a while because of that.

[MAsic12345]

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