Lift the lid on your Canon i9900 with the printer off, and then turn it on. Wait for the cartridge to stop moving and the green light to stop flashing and light steady-on. Remove all eight (!) cartridges and set them aside. Flip up the gray lever at the top-right of the carriage. The printhead is now loose, pick it up and pull it out. Unplug the printer.

There are two compatible printheads for this printer. One (the original) is the QQY6-0055, and the other (a later replacement) is the QY6-0076. To my knowledge, there are NO OTHER PRINTHEADS that are compatible with this printer.

The model of your printhead should be molded or stamped into the plastic somewhere on it. You will need good lighting to see it! (A flashlight is good for this.)

MY PRINTHEAD IS A QY6-0055. If you have the QY6-0076 printhead, you cannot help me (sorry), and you should follow the directions in Step One, in reverse order, to put your printhead back in the printer.

You will need a soldering iron, solder, and tweezers or fine needlenose pliers for this.

The printhead's circuitry consists of two principal parts. One is a green PCB with lots of contacts on one side, and a SOP-8 serial (SPI) ROM chip on the other. The second part is a flexible circuit board, silicone glued to the green PCB, that acts as a wiring harness to permit communication between the printer and the printhead's actual, er, head, where the ink comes out.

That green PCB is held on with four "heat stakes" -- plastic columns, integral to the plastic body of the printhead, that the circuit board has been placed over, where the tops of the columns have been melted to form a rivet-like cap over each hole in the PCB.

Gingerly remove the caps from the heat stakes and (more gingerly) pry the PCB loose -- be VERY careful -- the PCB is thin and silicone snot-glue can easily break. If the PCB cracks or the flexible circuit board comes loose, your printhead is permanently and irrevocably shot to heck and you ABSOLUTELY MUST buy a new one. Don't do that to yourself!

*ahem*

Once you have access to the back of the PCB, use a soldering iron to remove the chip. What worked for me was, using a Hakko 926 iron set to about 750 F and a conical tip, melting a little new solder (I use 60/40 and I don't care) onto the pins of the chip, and then laying the entire tip of the iron across all four pins on one side, then pulling up with a pair of needlenose pliers to free one side... then repeating this on the other side to get the chip off. Have patience, it takes a while. If you're worried about giving the chip heatstroke -- stop and let it cool, don't risk killing it. You can't read out from a dead ROM anyways.

This is the part we've been building up to. I use a TL866A programmer from eBay, and the "MiniPro" software that came with it. This model has been superseded, but use what you have that will work. For your information, the chip is a Seiko S93C56BR, a 2048-bit ROM organized as 128 words of 16 bits each. It is in a SOP-8 package. Depending on your programmer's software, you may have multiple pinout options to select from... at least for me, selecting the wrong one resulted in the chip simply not reading, and did not harm the chip -- YMMV.

If your programmer is like mine, you will need a SOP-to-DIP adapter module. My programmer came with one. Yours may or may not have... again, YMMV. If you don't have one, and you need it -- Amazon and eBay are both seriously chock full of the dang things, and they go for unbelievably tiny sums to boot. Get one. Solder the chip to it, gingerly, and insert the chip in its adapter into the programmer with the programmer OFF AND DISCONNECTED. Plug it in, turn it on, do your thing, and PM me the dump, preferably as an Intel *.hex file for consistency's sake. I'll put it up here as soon as I get it, and if enough people do this then maybe we'll all get something out of it.

Good luck. I haven't done this yet... I'm planning on reattaching the PCB with super glue. We'll see...